1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 1994 Linus Torvalds 4 * 5 * Cyrix stuff, June 1998 by: 6 * - Rafael R. Reilova (moved everything from head.S), 7 * <rreilova@ececs.uc.edu> 8 * - Channing Corn (tests & fixes), 9 * - Andrew D. Balsa (code cleanup). 10 */ 11 #include <linux/init.h> 12 #include <linux/cpu.h> 13 #include <linux/module.h> 14 #include <linux/nospec.h> 15 #include <linux/prctl.h> 16 #include <linux/sched/smt.h> 17 #include <linux/pgtable.h> 18 #include <linux/bpf.h> 19 20 #include <asm/spec-ctrl.h> 21 #include <asm/cmdline.h> 22 #include <asm/bugs.h> 23 #include <asm/processor.h> 24 #include <asm/processor-flags.h> 25 #include <asm/fpu/api.h> 26 #include <asm/msr.h> 27 #include <asm/vmx.h> 28 #include <asm/paravirt.h> 29 #include <asm/cpu_device_id.h> 30 #include <asm/e820/api.h> 31 #include <asm/hypervisor.h> 32 #include <asm/tlbflush.h> 33 #include <asm/cpu.h> 34 35 #include "cpu.h" 36 37 static void __init spectre_v1_select_mitigation(void); 38 static void __init spectre_v2_select_mitigation(void); 39 static void __init retbleed_select_mitigation(void); 40 static void __init spectre_v2_user_select_mitigation(void); 41 static void __init ssb_select_mitigation(void); 42 static void __init l1tf_select_mitigation(void); 43 static void __init mds_select_mitigation(void); 44 static void __init md_clear_update_mitigation(void); 45 static void __init md_clear_select_mitigation(void); 46 static void __init taa_select_mitigation(void); 47 static void __init mmio_select_mitigation(void); 48 static void __init srbds_select_mitigation(void); 49 static void __init l1d_flush_select_mitigation(void); 50 static void __init srso_select_mitigation(void); 51 static void __init gds_select_mitigation(void); 52 53 /* The base value of the SPEC_CTRL MSR without task-specific bits set */ 54 u64 x86_spec_ctrl_base; 55 EXPORT_SYMBOL_GPL(x86_spec_ctrl_base); 56 57 /* The current value of the SPEC_CTRL MSR with task-specific bits set */ 58 DEFINE_PER_CPU(u64, x86_spec_ctrl_current); 59 EXPORT_PER_CPU_SYMBOL_GPL(x86_spec_ctrl_current); 60 61 u64 x86_pred_cmd __ro_after_init = PRED_CMD_IBPB; 62 EXPORT_SYMBOL_GPL(x86_pred_cmd); 63 64 static u64 __ro_after_init x86_arch_cap_msr; 65 66 static DEFINE_MUTEX(spec_ctrl_mutex); 67 68 void (*x86_return_thunk)(void) __ro_after_init = __x86_return_thunk; 69 70 /* Update SPEC_CTRL MSR and its cached copy unconditionally */ 71 static void update_spec_ctrl(u64 val) 72 { 73 this_cpu_write(x86_spec_ctrl_current, val); 74 wrmsrl(MSR_IA32_SPEC_CTRL, val); 75 } 76 77 /* 78 * Keep track of the SPEC_CTRL MSR value for the current task, which may differ 79 * from x86_spec_ctrl_base due to STIBP/SSB in __speculation_ctrl_update(). 80 */ 81 void update_spec_ctrl_cond(u64 val) 82 { 83 if (this_cpu_read(x86_spec_ctrl_current) == val) 84 return; 85 86 this_cpu_write(x86_spec_ctrl_current, val); 87 88 /* 89 * When KERNEL_IBRS this MSR is written on return-to-user, unless 90 * forced the update can be delayed until that time. 91 */ 92 if (!cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS)) 93 wrmsrl(MSR_IA32_SPEC_CTRL, val); 94 } 95 96 noinstr u64 spec_ctrl_current(void) 97 { 98 return this_cpu_read(x86_spec_ctrl_current); 99 } 100 EXPORT_SYMBOL_GPL(spec_ctrl_current); 101 102 /* 103 * AMD specific MSR info for Speculative Store Bypass control. 104 * x86_amd_ls_cfg_ssbd_mask is initialized in identify_boot_cpu(). 105 */ 106 u64 __ro_after_init x86_amd_ls_cfg_base; 107 u64 __ro_after_init x86_amd_ls_cfg_ssbd_mask; 108 109 /* Control conditional STIBP in switch_to() */ 110 DEFINE_STATIC_KEY_FALSE(switch_to_cond_stibp); 111 /* Control conditional IBPB in switch_mm() */ 112 DEFINE_STATIC_KEY_FALSE(switch_mm_cond_ibpb); 113 /* Control unconditional IBPB in switch_mm() */ 114 DEFINE_STATIC_KEY_FALSE(switch_mm_always_ibpb); 115 116 /* Control MDS CPU buffer clear before idling (halt, mwait) */ 117 DEFINE_STATIC_KEY_FALSE(mds_idle_clear); 118 EXPORT_SYMBOL_GPL(mds_idle_clear); 119 120 /* 121 * Controls whether l1d flush based mitigations are enabled, 122 * based on hw features and admin setting via boot parameter 123 * defaults to false 124 */ 125 DEFINE_STATIC_KEY_FALSE(switch_mm_cond_l1d_flush); 126 127 /* Controls CPU Fill buffer clear before KVM guest MMIO accesses */ 128 DEFINE_STATIC_KEY_FALSE(mmio_stale_data_clear); 129 EXPORT_SYMBOL_GPL(mmio_stale_data_clear); 130 131 void __init cpu_select_mitigations(void) 132 { 133 /* 134 * Read the SPEC_CTRL MSR to account for reserved bits which may 135 * have unknown values. AMD64_LS_CFG MSR is cached in the early AMD 136 * init code as it is not enumerated and depends on the family. 137 */ 138 if (cpu_feature_enabled(X86_FEATURE_MSR_SPEC_CTRL)) { 139 rdmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base); 140 141 /* 142 * Previously running kernel (kexec), may have some controls 143 * turned ON. Clear them and let the mitigations setup below 144 * rediscover them based on configuration. 145 */ 146 x86_spec_ctrl_base &= ~SPEC_CTRL_MITIGATIONS_MASK; 147 } 148 149 x86_arch_cap_msr = x86_read_arch_cap_msr(); 150 151 /* Select the proper CPU mitigations before patching alternatives: */ 152 spectre_v1_select_mitigation(); 153 spectre_v2_select_mitigation(); 154 /* 155 * retbleed_select_mitigation() relies on the state set by 156 * spectre_v2_select_mitigation(); specifically it wants to know about 157 * spectre_v2=ibrs. 158 */ 159 retbleed_select_mitigation(); 160 /* 161 * spectre_v2_user_select_mitigation() relies on the state set by 162 * retbleed_select_mitigation(); specifically the STIBP selection is 163 * forced for UNRET or IBPB. 164 */ 165 spectre_v2_user_select_mitigation(); 166 ssb_select_mitigation(); 167 l1tf_select_mitigation(); 168 md_clear_select_mitigation(); 169 srbds_select_mitigation(); 170 l1d_flush_select_mitigation(); 171 172 /* 173 * srso_select_mitigation() depends and must run after 174 * retbleed_select_mitigation(). 175 */ 176 srso_select_mitigation(); 177 gds_select_mitigation(); 178 } 179 180 /* 181 * NOTE: This function is *only* called for SVM, since Intel uses 182 * MSR_IA32_SPEC_CTRL for SSBD. 183 */ 184 void 185 x86_virt_spec_ctrl(u64 guest_virt_spec_ctrl, bool setguest) 186 { 187 u64 guestval, hostval; 188 struct thread_info *ti = current_thread_info(); 189 190 /* 191 * If SSBD is not handled in MSR_SPEC_CTRL on AMD, update 192 * MSR_AMD64_L2_CFG or MSR_VIRT_SPEC_CTRL if supported. 193 */ 194 if (!static_cpu_has(X86_FEATURE_LS_CFG_SSBD) && 195 !static_cpu_has(X86_FEATURE_VIRT_SSBD)) 196 return; 197 198 /* 199 * If the host has SSBD mitigation enabled, force it in the host's 200 * virtual MSR value. If its not permanently enabled, evaluate 201 * current's TIF_SSBD thread flag. 202 */ 203 if (static_cpu_has(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE)) 204 hostval = SPEC_CTRL_SSBD; 205 else 206 hostval = ssbd_tif_to_spec_ctrl(ti->flags); 207 208 /* Sanitize the guest value */ 209 guestval = guest_virt_spec_ctrl & SPEC_CTRL_SSBD; 210 211 if (hostval != guestval) { 212 unsigned long tif; 213 214 tif = setguest ? ssbd_spec_ctrl_to_tif(guestval) : 215 ssbd_spec_ctrl_to_tif(hostval); 216 217 speculation_ctrl_update(tif); 218 } 219 } 220 EXPORT_SYMBOL_GPL(x86_virt_spec_ctrl); 221 222 static void x86_amd_ssb_disable(void) 223 { 224 u64 msrval = x86_amd_ls_cfg_base | x86_amd_ls_cfg_ssbd_mask; 225 226 if (boot_cpu_has(X86_FEATURE_VIRT_SSBD)) 227 wrmsrl(MSR_AMD64_VIRT_SPEC_CTRL, SPEC_CTRL_SSBD); 228 else if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD)) 229 wrmsrl(MSR_AMD64_LS_CFG, msrval); 230 } 231 232 #undef pr_fmt 233 #define pr_fmt(fmt) "MDS: " fmt 234 235 /* Default mitigation for MDS-affected CPUs */ 236 static enum mds_mitigations mds_mitigation __ro_after_init = MDS_MITIGATION_FULL; 237 static bool mds_nosmt __ro_after_init = false; 238 239 static const char * const mds_strings[] = { 240 [MDS_MITIGATION_OFF] = "Vulnerable", 241 [MDS_MITIGATION_FULL] = "Mitigation: Clear CPU buffers", 242 [MDS_MITIGATION_VMWERV] = "Vulnerable: Clear CPU buffers attempted, no microcode", 243 }; 244 245 static void __init mds_select_mitigation(void) 246 { 247 if (!boot_cpu_has_bug(X86_BUG_MDS) || cpu_mitigations_off()) { 248 mds_mitigation = MDS_MITIGATION_OFF; 249 return; 250 } 251 252 if (mds_mitigation == MDS_MITIGATION_FULL) { 253 if (!boot_cpu_has(X86_FEATURE_MD_CLEAR)) 254 mds_mitigation = MDS_MITIGATION_VMWERV; 255 256 setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF); 257 258 if (!boot_cpu_has(X86_BUG_MSBDS_ONLY) && 259 (mds_nosmt || cpu_mitigations_auto_nosmt())) 260 cpu_smt_disable(false); 261 } 262 } 263 264 static int __init mds_cmdline(char *str) 265 { 266 if (!boot_cpu_has_bug(X86_BUG_MDS)) 267 return 0; 268 269 if (!str) 270 return -EINVAL; 271 272 if (!strcmp(str, "off")) 273 mds_mitigation = MDS_MITIGATION_OFF; 274 else if (!strcmp(str, "full")) 275 mds_mitigation = MDS_MITIGATION_FULL; 276 else if (!strcmp(str, "full,nosmt")) { 277 mds_mitigation = MDS_MITIGATION_FULL; 278 mds_nosmt = true; 279 } 280 281 return 0; 282 } 283 early_param("mds", mds_cmdline); 284 285 #undef pr_fmt 286 #define pr_fmt(fmt) "TAA: " fmt 287 288 enum taa_mitigations { 289 TAA_MITIGATION_OFF, 290 TAA_MITIGATION_UCODE_NEEDED, 291 TAA_MITIGATION_VERW, 292 TAA_MITIGATION_TSX_DISABLED, 293 }; 294 295 /* Default mitigation for TAA-affected CPUs */ 296 static enum taa_mitigations taa_mitigation __ro_after_init = TAA_MITIGATION_VERW; 297 static bool taa_nosmt __ro_after_init; 298 299 static const char * const taa_strings[] = { 300 [TAA_MITIGATION_OFF] = "Vulnerable", 301 [TAA_MITIGATION_UCODE_NEEDED] = "Vulnerable: Clear CPU buffers attempted, no microcode", 302 [TAA_MITIGATION_VERW] = "Mitigation: Clear CPU buffers", 303 [TAA_MITIGATION_TSX_DISABLED] = "Mitigation: TSX disabled", 304 }; 305 306 static void __init taa_select_mitigation(void) 307 { 308 if (!boot_cpu_has_bug(X86_BUG_TAA)) { 309 taa_mitigation = TAA_MITIGATION_OFF; 310 return; 311 } 312 313 /* TSX previously disabled by tsx=off */ 314 if (!boot_cpu_has(X86_FEATURE_RTM)) { 315 taa_mitigation = TAA_MITIGATION_TSX_DISABLED; 316 return; 317 } 318 319 if (cpu_mitigations_off()) { 320 taa_mitigation = TAA_MITIGATION_OFF; 321 return; 322 } 323 324 /* 325 * TAA mitigation via VERW is turned off if both 326 * tsx_async_abort=off and mds=off are specified. 327 */ 328 if (taa_mitigation == TAA_MITIGATION_OFF && 329 mds_mitigation == MDS_MITIGATION_OFF) 330 return; 331 332 if (boot_cpu_has(X86_FEATURE_MD_CLEAR)) 333 taa_mitigation = TAA_MITIGATION_VERW; 334 else 335 taa_mitigation = TAA_MITIGATION_UCODE_NEEDED; 336 337 /* 338 * VERW doesn't clear the CPU buffers when MD_CLEAR=1 and MDS_NO=1. 339 * A microcode update fixes this behavior to clear CPU buffers. It also 340 * adds support for MSR_IA32_TSX_CTRL which is enumerated by the 341 * ARCH_CAP_TSX_CTRL_MSR bit. 342 * 343 * On MDS_NO=1 CPUs if ARCH_CAP_TSX_CTRL_MSR is not set, microcode 344 * update is required. 345 */ 346 if ( (x86_arch_cap_msr & ARCH_CAP_MDS_NO) && 347 !(x86_arch_cap_msr & ARCH_CAP_TSX_CTRL_MSR)) 348 taa_mitigation = TAA_MITIGATION_UCODE_NEEDED; 349 350 /* 351 * TSX is enabled, select alternate mitigation for TAA which is 352 * the same as MDS. Enable MDS static branch to clear CPU buffers. 353 * 354 * For guests that can't determine whether the correct microcode is 355 * present on host, enable the mitigation for UCODE_NEEDED as well. 356 */ 357 setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF); 358 359 if (taa_nosmt || cpu_mitigations_auto_nosmt()) 360 cpu_smt_disable(false); 361 } 362 363 static int __init tsx_async_abort_parse_cmdline(char *str) 364 { 365 if (!boot_cpu_has_bug(X86_BUG_TAA)) 366 return 0; 367 368 if (!str) 369 return -EINVAL; 370 371 if (!strcmp(str, "off")) { 372 taa_mitigation = TAA_MITIGATION_OFF; 373 } else if (!strcmp(str, "full")) { 374 taa_mitigation = TAA_MITIGATION_VERW; 375 } else if (!strcmp(str, "full,nosmt")) { 376 taa_mitigation = TAA_MITIGATION_VERW; 377 taa_nosmt = true; 378 } 379 380 return 0; 381 } 382 early_param("tsx_async_abort", tsx_async_abort_parse_cmdline); 383 384 #undef pr_fmt 385 #define pr_fmt(fmt) "MMIO Stale Data: " fmt 386 387 enum mmio_mitigations { 388 MMIO_MITIGATION_OFF, 389 MMIO_MITIGATION_UCODE_NEEDED, 390 MMIO_MITIGATION_VERW, 391 }; 392 393 /* Default mitigation for Processor MMIO Stale Data vulnerabilities */ 394 static enum mmio_mitigations mmio_mitigation __ro_after_init = MMIO_MITIGATION_VERW; 395 static bool mmio_nosmt __ro_after_init = false; 396 397 static const char * const mmio_strings[] = { 398 [MMIO_MITIGATION_OFF] = "Vulnerable", 399 [MMIO_MITIGATION_UCODE_NEEDED] = "Vulnerable: Clear CPU buffers attempted, no microcode", 400 [MMIO_MITIGATION_VERW] = "Mitigation: Clear CPU buffers", 401 }; 402 403 static void __init mmio_select_mitigation(void) 404 { 405 if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA) || 406 boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN) || 407 cpu_mitigations_off()) { 408 mmio_mitigation = MMIO_MITIGATION_OFF; 409 return; 410 } 411 412 if (mmio_mitigation == MMIO_MITIGATION_OFF) 413 return; 414 415 /* 416 * Enable CPU buffer clear mitigation for host and VMM, if also affected 417 * by MDS or TAA. Otherwise, enable mitigation for VMM only. 418 */ 419 if (boot_cpu_has_bug(X86_BUG_MDS) || (boot_cpu_has_bug(X86_BUG_TAA) && 420 boot_cpu_has(X86_FEATURE_RTM))) 421 setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF); 422 423 /* 424 * X86_FEATURE_CLEAR_CPU_BUF could be enabled by other VERW based 425 * mitigations, disable KVM-only mitigation in that case. 426 */ 427 if (boot_cpu_has(X86_FEATURE_CLEAR_CPU_BUF)) 428 static_branch_disable(&mmio_stale_data_clear); 429 else 430 static_branch_enable(&mmio_stale_data_clear); 431 432 /* 433 * If Processor-MMIO-Stale-Data bug is present and Fill Buffer data can 434 * be propagated to uncore buffers, clearing the Fill buffers on idle 435 * is required irrespective of SMT state. 436 */ 437 if (!(x86_arch_cap_msr & ARCH_CAP_FBSDP_NO)) 438 static_branch_enable(&mds_idle_clear); 439 440 /* 441 * Check if the system has the right microcode. 442 * 443 * CPU Fill buffer clear mitigation is enumerated by either an explicit 444 * FB_CLEAR or by the presence of both MD_CLEAR and L1D_FLUSH on MDS 445 * affected systems. 446 */ 447 if ((x86_arch_cap_msr & ARCH_CAP_FB_CLEAR) || 448 (boot_cpu_has(X86_FEATURE_MD_CLEAR) && 449 boot_cpu_has(X86_FEATURE_FLUSH_L1D) && 450 !(x86_arch_cap_msr & ARCH_CAP_MDS_NO))) 451 mmio_mitigation = MMIO_MITIGATION_VERW; 452 else 453 mmio_mitigation = MMIO_MITIGATION_UCODE_NEEDED; 454 455 if (mmio_nosmt || cpu_mitigations_auto_nosmt()) 456 cpu_smt_disable(false); 457 } 458 459 static int __init mmio_stale_data_parse_cmdline(char *str) 460 { 461 if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA)) 462 return 0; 463 464 if (!str) 465 return -EINVAL; 466 467 if (!strcmp(str, "off")) { 468 mmio_mitigation = MMIO_MITIGATION_OFF; 469 } else if (!strcmp(str, "full")) { 470 mmio_mitigation = MMIO_MITIGATION_VERW; 471 } else if (!strcmp(str, "full,nosmt")) { 472 mmio_mitigation = MMIO_MITIGATION_VERW; 473 mmio_nosmt = true; 474 } 475 476 return 0; 477 } 478 early_param("mmio_stale_data", mmio_stale_data_parse_cmdline); 479 480 #undef pr_fmt 481 #define pr_fmt(fmt) "Register File Data Sampling: " fmt 482 483 enum rfds_mitigations { 484 RFDS_MITIGATION_OFF, 485 RFDS_MITIGATION_VERW, 486 RFDS_MITIGATION_UCODE_NEEDED, 487 }; 488 489 /* Default mitigation for Register File Data Sampling */ 490 static enum rfds_mitigations rfds_mitigation __ro_after_init = 491 IS_ENABLED(CONFIG_MITIGATION_RFDS) ? RFDS_MITIGATION_VERW : RFDS_MITIGATION_OFF; 492 493 static const char * const rfds_strings[] = { 494 [RFDS_MITIGATION_OFF] = "Vulnerable", 495 [RFDS_MITIGATION_VERW] = "Mitigation: Clear Register File", 496 [RFDS_MITIGATION_UCODE_NEEDED] = "Vulnerable: No microcode", 497 }; 498 499 static void __init rfds_select_mitigation(void) 500 { 501 if (!boot_cpu_has_bug(X86_BUG_RFDS) || cpu_mitigations_off()) { 502 rfds_mitigation = RFDS_MITIGATION_OFF; 503 return; 504 } 505 if (rfds_mitigation == RFDS_MITIGATION_OFF) 506 return; 507 508 if (x86_arch_cap_msr & ARCH_CAP_RFDS_CLEAR) 509 setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF); 510 else 511 rfds_mitigation = RFDS_MITIGATION_UCODE_NEEDED; 512 } 513 514 static __init int rfds_parse_cmdline(char *str) 515 { 516 if (!str) 517 return -EINVAL; 518 519 if (!boot_cpu_has_bug(X86_BUG_RFDS)) 520 return 0; 521 522 if (!strcmp(str, "off")) 523 rfds_mitigation = RFDS_MITIGATION_OFF; 524 else if (!strcmp(str, "on")) 525 rfds_mitigation = RFDS_MITIGATION_VERW; 526 527 return 0; 528 } 529 early_param("reg_file_data_sampling", rfds_parse_cmdline); 530 531 #undef pr_fmt 532 #define pr_fmt(fmt) "" fmt 533 534 static void __init md_clear_update_mitigation(void) 535 { 536 if (cpu_mitigations_off()) 537 return; 538 539 if (!boot_cpu_has(X86_FEATURE_CLEAR_CPU_BUF)) 540 goto out; 541 542 /* 543 * X86_FEATURE_CLEAR_CPU_BUF is now enabled. Update MDS, TAA and MMIO 544 * Stale Data mitigation, if necessary. 545 */ 546 if (mds_mitigation == MDS_MITIGATION_OFF && 547 boot_cpu_has_bug(X86_BUG_MDS)) { 548 mds_mitigation = MDS_MITIGATION_FULL; 549 mds_select_mitigation(); 550 } 551 if (taa_mitigation == TAA_MITIGATION_OFF && 552 boot_cpu_has_bug(X86_BUG_TAA)) { 553 taa_mitigation = TAA_MITIGATION_VERW; 554 taa_select_mitigation(); 555 } 556 /* 557 * MMIO_MITIGATION_OFF is not checked here so that mmio_stale_data_clear 558 * gets updated correctly as per X86_FEATURE_CLEAR_CPU_BUF state. 559 */ 560 if (boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA)) { 561 mmio_mitigation = MMIO_MITIGATION_VERW; 562 mmio_select_mitigation(); 563 } 564 if (rfds_mitigation == RFDS_MITIGATION_OFF && 565 boot_cpu_has_bug(X86_BUG_RFDS)) { 566 rfds_mitigation = RFDS_MITIGATION_VERW; 567 rfds_select_mitigation(); 568 } 569 out: 570 if (boot_cpu_has_bug(X86_BUG_MDS)) 571 pr_info("MDS: %s\n", mds_strings[mds_mitigation]); 572 if (boot_cpu_has_bug(X86_BUG_TAA)) 573 pr_info("TAA: %s\n", taa_strings[taa_mitigation]); 574 if (boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA)) 575 pr_info("MMIO Stale Data: %s\n", mmio_strings[mmio_mitigation]); 576 else if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN)) 577 pr_info("MMIO Stale Data: Unknown: No mitigations\n"); 578 if (boot_cpu_has_bug(X86_BUG_RFDS)) 579 pr_info("Register File Data Sampling: %s\n", rfds_strings[rfds_mitigation]); 580 } 581 582 static void __init md_clear_select_mitigation(void) 583 { 584 mds_select_mitigation(); 585 taa_select_mitigation(); 586 mmio_select_mitigation(); 587 rfds_select_mitigation(); 588 589 /* 590 * As these mitigations are inter-related and rely on VERW instruction 591 * to clear the microarchitural buffers, update and print their status 592 * after mitigation selection is done for each of these vulnerabilities. 593 */ 594 md_clear_update_mitigation(); 595 } 596 597 #undef pr_fmt 598 #define pr_fmt(fmt) "SRBDS: " fmt 599 600 enum srbds_mitigations { 601 SRBDS_MITIGATION_OFF, 602 SRBDS_MITIGATION_UCODE_NEEDED, 603 SRBDS_MITIGATION_FULL, 604 SRBDS_MITIGATION_TSX_OFF, 605 SRBDS_MITIGATION_HYPERVISOR, 606 }; 607 608 static enum srbds_mitigations srbds_mitigation __ro_after_init = SRBDS_MITIGATION_FULL; 609 610 static const char * const srbds_strings[] = { 611 [SRBDS_MITIGATION_OFF] = "Vulnerable", 612 [SRBDS_MITIGATION_UCODE_NEEDED] = "Vulnerable: No microcode", 613 [SRBDS_MITIGATION_FULL] = "Mitigation: Microcode", 614 [SRBDS_MITIGATION_TSX_OFF] = "Mitigation: TSX disabled", 615 [SRBDS_MITIGATION_HYPERVISOR] = "Unknown: Dependent on hypervisor status", 616 }; 617 618 static bool srbds_off; 619 620 void update_srbds_msr(void) 621 { 622 u64 mcu_ctrl; 623 624 if (!boot_cpu_has_bug(X86_BUG_SRBDS)) 625 return; 626 627 if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) 628 return; 629 630 if (srbds_mitigation == SRBDS_MITIGATION_UCODE_NEEDED) 631 return; 632 633 /* 634 * A MDS_NO CPU for which SRBDS mitigation is not needed due to TSX 635 * being disabled and it hasn't received the SRBDS MSR microcode. 636 */ 637 if (!boot_cpu_has(X86_FEATURE_SRBDS_CTRL)) 638 return; 639 640 rdmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl); 641 642 switch (srbds_mitigation) { 643 case SRBDS_MITIGATION_OFF: 644 case SRBDS_MITIGATION_TSX_OFF: 645 mcu_ctrl |= RNGDS_MITG_DIS; 646 break; 647 case SRBDS_MITIGATION_FULL: 648 mcu_ctrl &= ~RNGDS_MITG_DIS; 649 break; 650 default: 651 break; 652 } 653 654 wrmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl); 655 } 656 657 static void __init srbds_select_mitigation(void) 658 { 659 if (!boot_cpu_has_bug(X86_BUG_SRBDS)) 660 return; 661 662 /* 663 * Check to see if this is one of the MDS_NO systems supporting TSX that 664 * are only exposed to SRBDS when TSX is enabled or when CPU is affected 665 * by Processor MMIO Stale Data vulnerability. 666 */ 667 if ((x86_arch_cap_msr & ARCH_CAP_MDS_NO) && !boot_cpu_has(X86_FEATURE_RTM) && 668 !boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA)) 669 srbds_mitigation = SRBDS_MITIGATION_TSX_OFF; 670 else if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) 671 srbds_mitigation = SRBDS_MITIGATION_HYPERVISOR; 672 else if (!boot_cpu_has(X86_FEATURE_SRBDS_CTRL)) 673 srbds_mitigation = SRBDS_MITIGATION_UCODE_NEEDED; 674 else if (cpu_mitigations_off() || srbds_off) 675 srbds_mitigation = SRBDS_MITIGATION_OFF; 676 677 update_srbds_msr(); 678 pr_info("%s\n", srbds_strings[srbds_mitigation]); 679 } 680 681 static int __init srbds_parse_cmdline(char *str) 682 { 683 if (!str) 684 return -EINVAL; 685 686 if (!boot_cpu_has_bug(X86_BUG_SRBDS)) 687 return 0; 688 689 srbds_off = !strcmp(str, "off"); 690 return 0; 691 } 692 early_param("srbds", srbds_parse_cmdline); 693 694 #undef pr_fmt 695 #define pr_fmt(fmt) "L1D Flush : " fmt 696 697 enum l1d_flush_mitigations { 698 L1D_FLUSH_OFF = 0, 699 L1D_FLUSH_ON, 700 }; 701 702 static enum l1d_flush_mitigations l1d_flush_mitigation __initdata = L1D_FLUSH_OFF; 703 704 static void __init l1d_flush_select_mitigation(void) 705 { 706 if (!l1d_flush_mitigation || !boot_cpu_has(X86_FEATURE_FLUSH_L1D)) 707 return; 708 709 static_branch_enable(&switch_mm_cond_l1d_flush); 710 pr_info("Conditional flush on switch_mm() enabled\n"); 711 } 712 713 static int __init l1d_flush_parse_cmdline(char *str) 714 { 715 if (!strcmp(str, "on")) 716 l1d_flush_mitigation = L1D_FLUSH_ON; 717 718 return 0; 719 } 720 early_param("l1d_flush", l1d_flush_parse_cmdline); 721 722 #undef pr_fmt 723 #define pr_fmt(fmt) "GDS: " fmt 724 725 enum gds_mitigations { 726 GDS_MITIGATION_OFF, 727 GDS_MITIGATION_UCODE_NEEDED, 728 GDS_MITIGATION_FORCE, 729 GDS_MITIGATION_FULL, 730 GDS_MITIGATION_FULL_LOCKED, 731 GDS_MITIGATION_HYPERVISOR, 732 }; 733 734 #if IS_ENABLED(CONFIG_MITIGATION_GDS_FORCE) 735 static enum gds_mitigations gds_mitigation __ro_after_init = GDS_MITIGATION_FORCE; 736 #else 737 static enum gds_mitigations gds_mitigation __ro_after_init = GDS_MITIGATION_FULL; 738 #endif 739 740 static const char * const gds_strings[] = { 741 [GDS_MITIGATION_OFF] = "Vulnerable", 742 [GDS_MITIGATION_UCODE_NEEDED] = "Vulnerable: No microcode", 743 [GDS_MITIGATION_FORCE] = "Mitigation: AVX disabled, no microcode", 744 [GDS_MITIGATION_FULL] = "Mitigation: Microcode", 745 [GDS_MITIGATION_FULL_LOCKED] = "Mitigation: Microcode (locked)", 746 [GDS_MITIGATION_HYPERVISOR] = "Unknown: Dependent on hypervisor status", 747 }; 748 749 bool gds_ucode_mitigated(void) 750 { 751 return (gds_mitigation == GDS_MITIGATION_FULL || 752 gds_mitigation == GDS_MITIGATION_FULL_LOCKED); 753 } 754 EXPORT_SYMBOL_GPL(gds_ucode_mitigated); 755 756 void update_gds_msr(void) 757 { 758 u64 mcu_ctrl_after; 759 u64 mcu_ctrl; 760 761 switch (gds_mitigation) { 762 case GDS_MITIGATION_OFF: 763 rdmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl); 764 mcu_ctrl |= GDS_MITG_DIS; 765 break; 766 case GDS_MITIGATION_FULL_LOCKED: 767 /* 768 * The LOCKED state comes from the boot CPU. APs might not have 769 * the same state. Make sure the mitigation is enabled on all 770 * CPUs. 771 */ 772 case GDS_MITIGATION_FULL: 773 rdmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl); 774 mcu_ctrl &= ~GDS_MITG_DIS; 775 break; 776 case GDS_MITIGATION_FORCE: 777 case GDS_MITIGATION_UCODE_NEEDED: 778 case GDS_MITIGATION_HYPERVISOR: 779 return; 780 } 781 782 wrmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl); 783 784 /* 785 * Check to make sure that the WRMSR value was not ignored. Writes to 786 * GDS_MITG_DIS will be ignored if this processor is locked but the boot 787 * processor was not. 788 */ 789 rdmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl_after); 790 WARN_ON_ONCE(mcu_ctrl != mcu_ctrl_after); 791 } 792 793 static void __init gds_select_mitigation(void) 794 { 795 u64 mcu_ctrl; 796 797 if (!boot_cpu_has_bug(X86_BUG_GDS)) 798 return; 799 800 if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) { 801 gds_mitigation = GDS_MITIGATION_HYPERVISOR; 802 goto out; 803 } 804 805 if (cpu_mitigations_off()) 806 gds_mitigation = GDS_MITIGATION_OFF; 807 /* Will verify below that mitigation _can_ be disabled */ 808 809 /* No microcode */ 810 if (!(x86_arch_cap_msr & ARCH_CAP_GDS_CTRL)) { 811 if (gds_mitigation == GDS_MITIGATION_FORCE) { 812 /* 813 * This only needs to be done on the boot CPU so do it 814 * here rather than in update_gds_msr() 815 */ 816 setup_clear_cpu_cap(X86_FEATURE_AVX); 817 pr_warn("Microcode update needed! Disabling AVX as mitigation.\n"); 818 } else { 819 gds_mitigation = GDS_MITIGATION_UCODE_NEEDED; 820 } 821 goto out; 822 } 823 824 /* Microcode has mitigation, use it */ 825 if (gds_mitigation == GDS_MITIGATION_FORCE) 826 gds_mitigation = GDS_MITIGATION_FULL; 827 828 rdmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl); 829 if (mcu_ctrl & GDS_MITG_LOCKED) { 830 if (gds_mitigation == GDS_MITIGATION_OFF) 831 pr_warn("Mitigation locked. Disable failed.\n"); 832 833 /* 834 * The mitigation is selected from the boot CPU. All other CPUs 835 * _should_ have the same state. If the boot CPU isn't locked 836 * but others are then update_gds_msr() will WARN() of the state 837 * mismatch. If the boot CPU is locked update_gds_msr() will 838 * ensure the other CPUs have the mitigation enabled. 839 */ 840 gds_mitigation = GDS_MITIGATION_FULL_LOCKED; 841 } 842 843 update_gds_msr(); 844 out: 845 pr_info("%s\n", gds_strings[gds_mitigation]); 846 } 847 848 static int __init gds_parse_cmdline(char *str) 849 { 850 if (!str) 851 return -EINVAL; 852 853 if (!boot_cpu_has_bug(X86_BUG_GDS)) 854 return 0; 855 856 if (!strcmp(str, "off")) 857 gds_mitigation = GDS_MITIGATION_OFF; 858 else if (!strcmp(str, "force")) 859 gds_mitigation = GDS_MITIGATION_FORCE; 860 861 return 0; 862 } 863 early_param("gather_data_sampling", gds_parse_cmdline); 864 865 #undef pr_fmt 866 #define pr_fmt(fmt) "Spectre V1 : " fmt 867 868 enum spectre_v1_mitigation { 869 SPECTRE_V1_MITIGATION_NONE, 870 SPECTRE_V1_MITIGATION_AUTO, 871 }; 872 873 static enum spectre_v1_mitigation spectre_v1_mitigation __ro_after_init = 874 SPECTRE_V1_MITIGATION_AUTO; 875 876 static const char * const spectre_v1_strings[] = { 877 [SPECTRE_V1_MITIGATION_NONE] = "Vulnerable: __user pointer sanitization and usercopy barriers only; no swapgs barriers", 878 [SPECTRE_V1_MITIGATION_AUTO] = "Mitigation: usercopy/swapgs barriers and __user pointer sanitization", 879 }; 880 881 /* 882 * Does SMAP provide full mitigation against speculative kernel access to 883 * userspace? 884 */ 885 static bool smap_works_speculatively(void) 886 { 887 if (!boot_cpu_has(X86_FEATURE_SMAP)) 888 return false; 889 890 /* 891 * On CPUs which are vulnerable to Meltdown, SMAP does not 892 * prevent speculative access to user data in the L1 cache. 893 * Consider SMAP to be non-functional as a mitigation on these 894 * CPUs. 895 */ 896 if (boot_cpu_has(X86_BUG_CPU_MELTDOWN)) 897 return false; 898 899 return true; 900 } 901 902 static void __init spectre_v1_select_mitigation(void) 903 { 904 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V1) || cpu_mitigations_off()) { 905 spectre_v1_mitigation = SPECTRE_V1_MITIGATION_NONE; 906 return; 907 } 908 909 if (spectre_v1_mitigation == SPECTRE_V1_MITIGATION_AUTO) { 910 /* 911 * With Spectre v1, a user can speculatively control either 912 * path of a conditional swapgs with a user-controlled GS 913 * value. The mitigation is to add lfences to both code paths. 914 * 915 * If FSGSBASE is enabled, the user can put a kernel address in 916 * GS, in which case SMAP provides no protection. 917 * 918 * If FSGSBASE is disabled, the user can only put a user space 919 * address in GS. That makes an attack harder, but still 920 * possible if there's no SMAP protection. 921 */ 922 if (boot_cpu_has(X86_FEATURE_FSGSBASE) || 923 !smap_works_speculatively()) { 924 /* 925 * Mitigation can be provided from SWAPGS itself or 926 * PTI as the CR3 write in the Meltdown mitigation 927 * is serializing. 928 * 929 * If neither is there, mitigate with an LFENCE to 930 * stop speculation through swapgs. 931 */ 932 if (boot_cpu_has_bug(X86_BUG_SWAPGS) && 933 !boot_cpu_has(X86_FEATURE_PTI)) 934 setup_force_cpu_cap(X86_FEATURE_FENCE_SWAPGS_USER); 935 936 /* 937 * Enable lfences in the kernel entry (non-swapgs) 938 * paths, to prevent user entry from speculatively 939 * skipping swapgs. 940 */ 941 setup_force_cpu_cap(X86_FEATURE_FENCE_SWAPGS_KERNEL); 942 } 943 } 944 945 pr_info("%s\n", spectre_v1_strings[spectre_v1_mitigation]); 946 } 947 948 static int __init nospectre_v1_cmdline(char *str) 949 { 950 spectre_v1_mitigation = SPECTRE_V1_MITIGATION_NONE; 951 return 0; 952 } 953 early_param("nospectre_v1", nospectre_v1_cmdline); 954 955 enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init = SPECTRE_V2_NONE; 956 957 #undef pr_fmt 958 #define pr_fmt(fmt) "RETBleed: " fmt 959 960 enum retbleed_mitigation { 961 RETBLEED_MITIGATION_NONE, 962 RETBLEED_MITIGATION_UNRET, 963 RETBLEED_MITIGATION_IBPB, 964 RETBLEED_MITIGATION_IBRS, 965 RETBLEED_MITIGATION_EIBRS, 966 RETBLEED_MITIGATION_STUFF, 967 }; 968 969 enum retbleed_mitigation_cmd { 970 RETBLEED_CMD_OFF, 971 RETBLEED_CMD_AUTO, 972 RETBLEED_CMD_UNRET, 973 RETBLEED_CMD_IBPB, 974 RETBLEED_CMD_STUFF, 975 }; 976 977 static const char * const retbleed_strings[] = { 978 [RETBLEED_MITIGATION_NONE] = "Vulnerable", 979 [RETBLEED_MITIGATION_UNRET] = "Mitigation: untrained return thunk", 980 [RETBLEED_MITIGATION_IBPB] = "Mitigation: IBPB", 981 [RETBLEED_MITIGATION_IBRS] = "Mitigation: IBRS", 982 [RETBLEED_MITIGATION_EIBRS] = "Mitigation: Enhanced IBRS", 983 [RETBLEED_MITIGATION_STUFF] = "Mitigation: Stuffing", 984 }; 985 986 static enum retbleed_mitigation retbleed_mitigation __ro_after_init = 987 RETBLEED_MITIGATION_NONE; 988 static enum retbleed_mitigation_cmd retbleed_cmd __ro_after_init = 989 RETBLEED_CMD_AUTO; 990 991 static int __ro_after_init retbleed_nosmt = false; 992 993 static int __init retbleed_parse_cmdline(char *str) 994 { 995 if (!str) 996 return -EINVAL; 997 998 while (str) { 999 char *next = strchr(str, ','); 1000 if (next) { 1001 *next = 0; 1002 next++; 1003 } 1004 1005 if (!strcmp(str, "off")) { 1006 retbleed_cmd = RETBLEED_CMD_OFF; 1007 } else if (!strcmp(str, "auto")) { 1008 retbleed_cmd = RETBLEED_CMD_AUTO; 1009 } else if (!strcmp(str, "unret")) { 1010 retbleed_cmd = RETBLEED_CMD_UNRET; 1011 } else if (!strcmp(str, "ibpb")) { 1012 retbleed_cmd = RETBLEED_CMD_IBPB; 1013 } else if (!strcmp(str, "stuff")) { 1014 retbleed_cmd = RETBLEED_CMD_STUFF; 1015 } else if (!strcmp(str, "nosmt")) { 1016 retbleed_nosmt = true; 1017 } else if (!strcmp(str, "force")) { 1018 setup_force_cpu_bug(X86_BUG_RETBLEED); 1019 } else { 1020 pr_err("Ignoring unknown retbleed option (%s).", str); 1021 } 1022 1023 str = next; 1024 } 1025 1026 return 0; 1027 } 1028 early_param("retbleed", retbleed_parse_cmdline); 1029 1030 #define RETBLEED_UNTRAIN_MSG "WARNING: BTB untrained return thunk mitigation is only effective on AMD/Hygon!\n" 1031 #define RETBLEED_INTEL_MSG "WARNING: Spectre v2 mitigation leaves CPU vulnerable to RETBleed attacks, data leaks possible!\n" 1032 1033 static void __init retbleed_select_mitigation(void) 1034 { 1035 bool mitigate_smt = false; 1036 1037 if (!boot_cpu_has_bug(X86_BUG_RETBLEED) || cpu_mitigations_off()) 1038 return; 1039 1040 switch (retbleed_cmd) { 1041 case RETBLEED_CMD_OFF: 1042 return; 1043 1044 case RETBLEED_CMD_UNRET: 1045 if (IS_ENABLED(CONFIG_MITIGATION_UNRET_ENTRY)) { 1046 retbleed_mitigation = RETBLEED_MITIGATION_UNRET; 1047 } else { 1048 pr_err("WARNING: kernel not compiled with MITIGATION_UNRET_ENTRY.\n"); 1049 goto do_cmd_auto; 1050 } 1051 break; 1052 1053 case RETBLEED_CMD_IBPB: 1054 if (!boot_cpu_has(X86_FEATURE_IBPB)) { 1055 pr_err("WARNING: CPU does not support IBPB.\n"); 1056 goto do_cmd_auto; 1057 } else if (IS_ENABLED(CONFIG_MITIGATION_IBPB_ENTRY)) { 1058 retbleed_mitigation = RETBLEED_MITIGATION_IBPB; 1059 } else { 1060 pr_err("WARNING: kernel not compiled with MITIGATION_IBPB_ENTRY.\n"); 1061 goto do_cmd_auto; 1062 } 1063 break; 1064 1065 case RETBLEED_CMD_STUFF: 1066 if (IS_ENABLED(CONFIG_MITIGATION_CALL_DEPTH_TRACKING) && 1067 spectre_v2_enabled == SPECTRE_V2_RETPOLINE) { 1068 retbleed_mitigation = RETBLEED_MITIGATION_STUFF; 1069 1070 } else { 1071 if (IS_ENABLED(CONFIG_MITIGATION_CALL_DEPTH_TRACKING)) 1072 pr_err("WARNING: retbleed=stuff depends on spectre_v2=retpoline\n"); 1073 else 1074 pr_err("WARNING: kernel not compiled with MITIGATION_CALL_DEPTH_TRACKING.\n"); 1075 1076 goto do_cmd_auto; 1077 } 1078 break; 1079 1080 do_cmd_auto: 1081 case RETBLEED_CMD_AUTO: 1082 if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || 1083 boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) { 1084 if (IS_ENABLED(CONFIG_MITIGATION_UNRET_ENTRY)) 1085 retbleed_mitigation = RETBLEED_MITIGATION_UNRET; 1086 else if (IS_ENABLED(CONFIG_MITIGATION_IBPB_ENTRY) && 1087 boot_cpu_has(X86_FEATURE_IBPB)) 1088 retbleed_mitigation = RETBLEED_MITIGATION_IBPB; 1089 } 1090 1091 /* 1092 * The Intel mitigation (IBRS or eIBRS) was already selected in 1093 * spectre_v2_select_mitigation(). 'retbleed_mitigation' will 1094 * be set accordingly below. 1095 */ 1096 1097 break; 1098 } 1099 1100 switch (retbleed_mitigation) { 1101 case RETBLEED_MITIGATION_UNRET: 1102 setup_force_cpu_cap(X86_FEATURE_RETHUNK); 1103 setup_force_cpu_cap(X86_FEATURE_UNRET); 1104 1105 x86_return_thunk = retbleed_return_thunk; 1106 1107 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD && 1108 boot_cpu_data.x86_vendor != X86_VENDOR_HYGON) 1109 pr_err(RETBLEED_UNTRAIN_MSG); 1110 1111 mitigate_smt = true; 1112 break; 1113 1114 case RETBLEED_MITIGATION_IBPB: 1115 setup_force_cpu_cap(X86_FEATURE_ENTRY_IBPB); 1116 setup_force_cpu_cap(X86_FEATURE_IBPB_ON_VMEXIT); 1117 mitigate_smt = true; 1118 break; 1119 1120 case RETBLEED_MITIGATION_STUFF: 1121 setup_force_cpu_cap(X86_FEATURE_RETHUNK); 1122 setup_force_cpu_cap(X86_FEATURE_CALL_DEPTH); 1123 1124 x86_return_thunk = call_depth_return_thunk; 1125 break; 1126 1127 default: 1128 break; 1129 } 1130 1131 if (mitigate_smt && !boot_cpu_has(X86_FEATURE_STIBP) && 1132 (retbleed_nosmt || cpu_mitigations_auto_nosmt())) 1133 cpu_smt_disable(false); 1134 1135 /* 1136 * Let IBRS trump all on Intel without affecting the effects of the 1137 * retbleed= cmdline option except for call depth based stuffing 1138 */ 1139 if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) { 1140 switch (spectre_v2_enabled) { 1141 case SPECTRE_V2_IBRS: 1142 retbleed_mitigation = RETBLEED_MITIGATION_IBRS; 1143 break; 1144 case SPECTRE_V2_EIBRS: 1145 case SPECTRE_V2_EIBRS_RETPOLINE: 1146 case SPECTRE_V2_EIBRS_LFENCE: 1147 retbleed_mitigation = RETBLEED_MITIGATION_EIBRS; 1148 break; 1149 default: 1150 if (retbleed_mitigation != RETBLEED_MITIGATION_STUFF) 1151 pr_err(RETBLEED_INTEL_MSG); 1152 } 1153 } 1154 1155 pr_info("%s\n", retbleed_strings[retbleed_mitigation]); 1156 } 1157 1158 #undef pr_fmt 1159 #define pr_fmt(fmt) "Spectre V2 : " fmt 1160 1161 static enum spectre_v2_user_mitigation spectre_v2_user_stibp __ro_after_init = 1162 SPECTRE_V2_USER_NONE; 1163 static enum spectre_v2_user_mitigation spectre_v2_user_ibpb __ro_after_init = 1164 SPECTRE_V2_USER_NONE; 1165 1166 #ifdef CONFIG_MITIGATION_RETPOLINE 1167 static bool spectre_v2_bad_module; 1168 1169 bool retpoline_module_ok(bool has_retpoline) 1170 { 1171 if (spectre_v2_enabled == SPECTRE_V2_NONE || has_retpoline) 1172 return true; 1173 1174 pr_err("System may be vulnerable to spectre v2\n"); 1175 spectre_v2_bad_module = true; 1176 return false; 1177 } 1178 1179 static inline const char *spectre_v2_module_string(void) 1180 { 1181 return spectre_v2_bad_module ? " - vulnerable module loaded" : ""; 1182 } 1183 #else 1184 static inline const char *spectre_v2_module_string(void) { return ""; } 1185 #endif 1186 1187 #define SPECTRE_V2_LFENCE_MSG "WARNING: LFENCE mitigation is not recommended for this CPU, data leaks possible!\n" 1188 #define SPECTRE_V2_EIBRS_EBPF_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS on, data leaks possible via Spectre v2 BHB attacks!\n" 1189 #define SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS+LFENCE mitigation and SMT, data leaks possible via Spectre v2 BHB attacks!\n" 1190 #define SPECTRE_V2_IBRS_PERF_MSG "WARNING: IBRS mitigation selected on Enhanced IBRS CPU, this may cause unnecessary performance loss\n" 1191 1192 #ifdef CONFIG_BPF_SYSCALL 1193 void unpriv_ebpf_notify(int new_state) 1194 { 1195 if (new_state) 1196 return; 1197 1198 /* Unprivileged eBPF is enabled */ 1199 1200 switch (spectre_v2_enabled) { 1201 case SPECTRE_V2_EIBRS: 1202 pr_err(SPECTRE_V2_EIBRS_EBPF_MSG); 1203 break; 1204 case SPECTRE_V2_EIBRS_LFENCE: 1205 if (sched_smt_active()) 1206 pr_err(SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG); 1207 break; 1208 default: 1209 break; 1210 } 1211 } 1212 #endif 1213 1214 static inline bool match_option(const char *arg, int arglen, const char *opt) 1215 { 1216 int len = strlen(opt); 1217 1218 return len == arglen && !strncmp(arg, opt, len); 1219 } 1220 1221 /* The kernel command line selection for spectre v2 */ 1222 enum spectre_v2_mitigation_cmd { 1223 SPECTRE_V2_CMD_NONE, 1224 SPECTRE_V2_CMD_AUTO, 1225 SPECTRE_V2_CMD_FORCE, 1226 SPECTRE_V2_CMD_RETPOLINE, 1227 SPECTRE_V2_CMD_RETPOLINE_GENERIC, 1228 SPECTRE_V2_CMD_RETPOLINE_LFENCE, 1229 SPECTRE_V2_CMD_EIBRS, 1230 SPECTRE_V2_CMD_EIBRS_RETPOLINE, 1231 SPECTRE_V2_CMD_EIBRS_LFENCE, 1232 SPECTRE_V2_CMD_IBRS, 1233 }; 1234 1235 enum spectre_v2_user_cmd { 1236 SPECTRE_V2_USER_CMD_NONE, 1237 SPECTRE_V2_USER_CMD_AUTO, 1238 SPECTRE_V2_USER_CMD_FORCE, 1239 SPECTRE_V2_USER_CMD_PRCTL, 1240 SPECTRE_V2_USER_CMD_PRCTL_IBPB, 1241 SPECTRE_V2_USER_CMD_SECCOMP, 1242 SPECTRE_V2_USER_CMD_SECCOMP_IBPB, 1243 }; 1244 1245 static const char * const spectre_v2_user_strings[] = { 1246 [SPECTRE_V2_USER_NONE] = "User space: Vulnerable", 1247 [SPECTRE_V2_USER_STRICT] = "User space: Mitigation: STIBP protection", 1248 [SPECTRE_V2_USER_STRICT_PREFERRED] = "User space: Mitigation: STIBP always-on protection", 1249 [SPECTRE_V2_USER_PRCTL] = "User space: Mitigation: STIBP via prctl", 1250 [SPECTRE_V2_USER_SECCOMP] = "User space: Mitigation: STIBP via seccomp and prctl", 1251 }; 1252 1253 static const struct { 1254 const char *option; 1255 enum spectre_v2_user_cmd cmd; 1256 bool secure; 1257 } v2_user_options[] __initconst = { 1258 { "auto", SPECTRE_V2_USER_CMD_AUTO, false }, 1259 { "off", SPECTRE_V2_USER_CMD_NONE, false }, 1260 { "on", SPECTRE_V2_USER_CMD_FORCE, true }, 1261 { "prctl", SPECTRE_V2_USER_CMD_PRCTL, false }, 1262 { "prctl,ibpb", SPECTRE_V2_USER_CMD_PRCTL_IBPB, false }, 1263 { "seccomp", SPECTRE_V2_USER_CMD_SECCOMP, false }, 1264 { "seccomp,ibpb", SPECTRE_V2_USER_CMD_SECCOMP_IBPB, false }, 1265 }; 1266 1267 static void __init spec_v2_user_print_cond(const char *reason, bool secure) 1268 { 1269 if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2) != secure) 1270 pr_info("spectre_v2_user=%s forced on command line.\n", reason); 1271 } 1272 1273 static __ro_after_init enum spectre_v2_mitigation_cmd spectre_v2_cmd; 1274 1275 static enum spectre_v2_user_cmd __init 1276 spectre_v2_parse_user_cmdline(void) 1277 { 1278 char arg[20]; 1279 int ret, i; 1280 1281 switch (spectre_v2_cmd) { 1282 case SPECTRE_V2_CMD_NONE: 1283 return SPECTRE_V2_USER_CMD_NONE; 1284 case SPECTRE_V2_CMD_FORCE: 1285 return SPECTRE_V2_USER_CMD_FORCE; 1286 default: 1287 break; 1288 } 1289 1290 ret = cmdline_find_option(boot_command_line, "spectre_v2_user", 1291 arg, sizeof(arg)); 1292 if (ret < 0) 1293 return SPECTRE_V2_USER_CMD_AUTO; 1294 1295 for (i = 0; i < ARRAY_SIZE(v2_user_options); i++) { 1296 if (match_option(arg, ret, v2_user_options[i].option)) { 1297 spec_v2_user_print_cond(v2_user_options[i].option, 1298 v2_user_options[i].secure); 1299 return v2_user_options[i].cmd; 1300 } 1301 } 1302 1303 pr_err("Unknown user space protection option (%s). Switching to AUTO select\n", arg); 1304 return SPECTRE_V2_USER_CMD_AUTO; 1305 } 1306 1307 static inline bool spectre_v2_in_ibrs_mode(enum spectre_v2_mitigation mode) 1308 { 1309 return spectre_v2_in_eibrs_mode(mode) || mode == SPECTRE_V2_IBRS; 1310 } 1311 1312 static void __init 1313 spectre_v2_user_select_mitigation(void) 1314 { 1315 enum spectre_v2_user_mitigation mode = SPECTRE_V2_USER_NONE; 1316 bool smt_possible = IS_ENABLED(CONFIG_SMP); 1317 enum spectre_v2_user_cmd cmd; 1318 1319 if (!boot_cpu_has(X86_FEATURE_IBPB) && !boot_cpu_has(X86_FEATURE_STIBP)) 1320 return; 1321 1322 if (cpu_smt_control == CPU_SMT_FORCE_DISABLED || 1323 cpu_smt_control == CPU_SMT_NOT_SUPPORTED) 1324 smt_possible = false; 1325 1326 cmd = spectre_v2_parse_user_cmdline(); 1327 switch (cmd) { 1328 case SPECTRE_V2_USER_CMD_NONE: 1329 goto set_mode; 1330 case SPECTRE_V2_USER_CMD_FORCE: 1331 mode = SPECTRE_V2_USER_STRICT; 1332 break; 1333 case SPECTRE_V2_USER_CMD_AUTO: 1334 case SPECTRE_V2_USER_CMD_PRCTL: 1335 case SPECTRE_V2_USER_CMD_PRCTL_IBPB: 1336 mode = SPECTRE_V2_USER_PRCTL; 1337 break; 1338 case SPECTRE_V2_USER_CMD_SECCOMP: 1339 case SPECTRE_V2_USER_CMD_SECCOMP_IBPB: 1340 if (IS_ENABLED(CONFIG_SECCOMP)) 1341 mode = SPECTRE_V2_USER_SECCOMP; 1342 else 1343 mode = SPECTRE_V2_USER_PRCTL; 1344 break; 1345 } 1346 1347 /* Initialize Indirect Branch Prediction Barrier */ 1348 if (boot_cpu_has(X86_FEATURE_IBPB)) { 1349 setup_force_cpu_cap(X86_FEATURE_USE_IBPB); 1350 1351 spectre_v2_user_ibpb = mode; 1352 switch (cmd) { 1353 case SPECTRE_V2_USER_CMD_NONE: 1354 break; 1355 case SPECTRE_V2_USER_CMD_FORCE: 1356 case SPECTRE_V2_USER_CMD_PRCTL_IBPB: 1357 case SPECTRE_V2_USER_CMD_SECCOMP_IBPB: 1358 static_branch_enable(&switch_mm_always_ibpb); 1359 spectre_v2_user_ibpb = SPECTRE_V2_USER_STRICT; 1360 break; 1361 case SPECTRE_V2_USER_CMD_PRCTL: 1362 case SPECTRE_V2_USER_CMD_AUTO: 1363 case SPECTRE_V2_USER_CMD_SECCOMP: 1364 static_branch_enable(&switch_mm_cond_ibpb); 1365 break; 1366 } 1367 1368 pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n", 1369 static_key_enabled(&switch_mm_always_ibpb) ? 1370 "always-on" : "conditional"); 1371 } 1372 1373 /* 1374 * If no STIBP, Intel enhanced IBRS is enabled, or SMT impossible, STIBP 1375 * is not required. 1376 * 1377 * Intel's Enhanced IBRS also protects against cross-thread branch target 1378 * injection in user-mode as the IBRS bit remains always set which 1379 * implicitly enables cross-thread protections. However, in legacy IBRS 1380 * mode, the IBRS bit is set only on kernel entry and cleared on return 1381 * to userspace. AMD Automatic IBRS also does not protect userspace. 1382 * These modes therefore disable the implicit cross-thread protection, 1383 * so allow for STIBP to be selected in those cases. 1384 */ 1385 if (!boot_cpu_has(X86_FEATURE_STIBP) || 1386 !smt_possible || 1387 (spectre_v2_in_eibrs_mode(spectre_v2_enabled) && 1388 !boot_cpu_has(X86_FEATURE_AUTOIBRS))) 1389 return; 1390 1391 /* 1392 * At this point, an STIBP mode other than "off" has been set. 1393 * If STIBP support is not being forced, check if STIBP always-on 1394 * is preferred. 1395 */ 1396 if (mode != SPECTRE_V2_USER_STRICT && 1397 boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON)) 1398 mode = SPECTRE_V2_USER_STRICT_PREFERRED; 1399 1400 if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET || 1401 retbleed_mitigation == RETBLEED_MITIGATION_IBPB) { 1402 if (mode != SPECTRE_V2_USER_STRICT && 1403 mode != SPECTRE_V2_USER_STRICT_PREFERRED) 1404 pr_info("Selecting STIBP always-on mode to complement retbleed mitigation\n"); 1405 mode = SPECTRE_V2_USER_STRICT_PREFERRED; 1406 } 1407 1408 spectre_v2_user_stibp = mode; 1409 1410 set_mode: 1411 pr_info("%s\n", spectre_v2_user_strings[mode]); 1412 } 1413 1414 static const char * const spectre_v2_strings[] = { 1415 [SPECTRE_V2_NONE] = "Vulnerable", 1416 [SPECTRE_V2_RETPOLINE] = "Mitigation: Retpolines", 1417 [SPECTRE_V2_LFENCE] = "Mitigation: LFENCE", 1418 [SPECTRE_V2_EIBRS] = "Mitigation: Enhanced / Automatic IBRS", 1419 [SPECTRE_V2_EIBRS_LFENCE] = "Mitigation: Enhanced / Automatic IBRS + LFENCE", 1420 [SPECTRE_V2_EIBRS_RETPOLINE] = "Mitigation: Enhanced / Automatic IBRS + Retpolines", 1421 [SPECTRE_V2_IBRS] = "Mitigation: IBRS", 1422 }; 1423 1424 static const struct { 1425 const char *option; 1426 enum spectre_v2_mitigation_cmd cmd; 1427 bool secure; 1428 } mitigation_options[] __initconst = { 1429 { "off", SPECTRE_V2_CMD_NONE, false }, 1430 { "on", SPECTRE_V2_CMD_FORCE, true }, 1431 { "retpoline", SPECTRE_V2_CMD_RETPOLINE, false }, 1432 { "retpoline,amd", SPECTRE_V2_CMD_RETPOLINE_LFENCE, false }, 1433 { "retpoline,lfence", SPECTRE_V2_CMD_RETPOLINE_LFENCE, false }, 1434 { "retpoline,generic", SPECTRE_V2_CMD_RETPOLINE_GENERIC, false }, 1435 { "eibrs", SPECTRE_V2_CMD_EIBRS, false }, 1436 { "eibrs,lfence", SPECTRE_V2_CMD_EIBRS_LFENCE, false }, 1437 { "eibrs,retpoline", SPECTRE_V2_CMD_EIBRS_RETPOLINE, false }, 1438 { "auto", SPECTRE_V2_CMD_AUTO, false }, 1439 { "ibrs", SPECTRE_V2_CMD_IBRS, false }, 1440 }; 1441 1442 static void __init spec_v2_print_cond(const char *reason, bool secure) 1443 { 1444 if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2) != secure) 1445 pr_info("%s selected on command line.\n", reason); 1446 } 1447 1448 static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void) 1449 { 1450 enum spectre_v2_mitigation_cmd cmd = SPECTRE_V2_CMD_AUTO; 1451 char arg[20]; 1452 int ret, i; 1453 1454 if (cmdline_find_option_bool(boot_command_line, "nospectre_v2") || 1455 cpu_mitigations_off()) 1456 return SPECTRE_V2_CMD_NONE; 1457 1458 ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, sizeof(arg)); 1459 if (ret < 0) 1460 return SPECTRE_V2_CMD_AUTO; 1461 1462 for (i = 0; i < ARRAY_SIZE(mitigation_options); i++) { 1463 if (!match_option(arg, ret, mitigation_options[i].option)) 1464 continue; 1465 cmd = mitigation_options[i].cmd; 1466 break; 1467 } 1468 1469 if (i >= ARRAY_SIZE(mitigation_options)) { 1470 pr_err("unknown option (%s). Switching to AUTO select\n", arg); 1471 return SPECTRE_V2_CMD_AUTO; 1472 } 1473 1474 if ((cmd == SPECTRE_V2_CMD_RETPOLINE || 1475 cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE || 1476 cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC || 1477 cmd == SPECTRE_V2_CMD_EIBRS_LFENCE || 1478 cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) && 1479 !IS_ENABLED(CONFIG_MITIGATION_RETPOLINE)) { 1480 pr_err("%s selected but not compiled in. Switching to AUTO select\n", 1481 mitigation_options[i].option); 1482 return SPECTRE_V2_CMD_AUTO; 1483 } 1484 1485 if ((cmd == SPECTRE_V2_CMD_EIBRS || 1486 cmd == SPECTRE_V2_CMD_EIBRS_LFENCE || 1487 cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) && 1488 !boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) { 1489 pr_err("%s selected but CPU doesn't have Enhanced or Automatic IBRS. Switching to AUTO select\n", 1490 mitigation_options[i].option); 1491 return SPECTRE_V2_CMD_AUTO; 1492 } 1493 1494 if ((cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE || 1495 cmd == SPECTRE_V2_CMD_EIBRS_LFENCE) && 1496 !boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) { 1497 pr_err("%s selected, but CPU doesn't have a serializing LFENCE. Switching to AUTO select\n", 1498 mitigation_options[i].option); 1499 return SPECTRE_V2_CMD_AUTO; 1500 } 1501 1502 if (cmd == SPECTRE_V2_CMD_IBRS && !IS_ENABLED(CONFIG_MITIGATION_IBRS_ENTRY)) { 1503 pr_err("%s selected but not compiled in. Switching to AUTO select\n", 1504 mitigation_options[i].option); 1505 return SPECTRE_V2_CMD_AUTO; 1506 } 1507 1508 if (cmd == SPECTRE_V2_CMD_IBRS && boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) { 1509 pr_err("%s selected but not Intel CPU. Switching to AUTO select\n", 1510 mitigation_options[i].option); 1511 return SPECTRE_V2_CMD_AUTO; 1512 } 1513 1514 if (cmd == SPECTRE_V2_CMD_IBRS && !boot_cpu_has(X86_FEATURE_IBRS)) { 1515 pr_err("%s selected but CPU doesn't have IBRS. Switching to AUTO select\n", 1516 mitigation_options[i].option); 1517 return SPECTRE_V2_CMD_AUTO; 1518 } 1519 1520 if (cmd == SPECTRE_V2_CMD_IBRS && cpu_feature_enabled(X86_FEATURE_XENPV)) { 1521 pr_err("%s selected but running as XenPV guest. Switching to AUTO select\n", 1522 mitigation_options[i].option); 1523 return SPECTRE_V2_CMD_AUTO; 1524 } 1525 1526 spec_v2_print_cond(mitigation_options[i].option, 1527 mitigation_options[i].secure); 1528 return cmd; 1529 } 1530 1531 static enum spectre_v2_mitigation __init spectre_v2_select_retpoline(void) 1532 { 1533 if (!IS_ENABLED(CONFIG_MITIGATION_RETPOLINE)) { 1534 pr_err("Kernel not compiled with retpoline; no mitigation available!"); 1535 return SPECTRE_V2_NONE; 1536 } 1537 1538 return SPECTRE_V2_RETPOLINE; 1539 } 1540 1541 static bool __ro_after_init rrsba_disabled; 1542 1543 /* Disable in-kernel use of non-RSB RET predictors */ 1544 static void __init spec_ctrl_disable_kernel_rrsba(void) 1545 { 1546 if (rrsba_disabled) 1547 return; 1548 1549 if (!(x86_arch_cap_msr & ARCH_CAP_RRSBA)) { 1550 rrsba_disabled = true; 1551 return; 1552 } 1553 1554 if (!boot_cpu_has(X86_FEATURE_RRSBA_CTRL)) 1555 return; 1556 1557 x86_spec_ctrl_base |= SPEC_CTRL_RRSBA_DIS_S; 1558 update_spec_ctrl(x86_spec_ctrl_base); 1559 rrsba_disabled = true; 1560 } 1561 1562 static void __init spectre_v2_determine_rsb_fill_type_at_vmexit(enum spectre_v2_mitigation mode) 1563 { 1564 /* 1565 * Similar to context switches, there are two types of RSB attacks 1566 * after VM exit: 1567 * 1568 * 1) RSB underflow 1569 * 1570 * 2) Poisoned RSB entry 1571 * 1572 * When retpoline is enabled, both are mitigated by filling/clearing 1573 * the RSB. 1574 * 1575 * When IBRS is enabled, while #1 would be mitigated by the IBRS branch 1576 * prediction isolation protections, RSB still needs to be cleared 1577 * because of #2. Note that SMEP provides no protection here, unlike 1578 * user-space-poisoned RSB entries. 1579 * 1580 * eIBRS should protect against RSB poisoning, but if the EIBRS_PBRSB 1581 * bug is present then a LITE version of RSB protection is required, 1582 * just a single call needs to retire before a RET is executed. 1583 */ 1584 switch (mode) { 1585 case SPECTRE_V2_NONE: 1586 return; 1587 1588 case SPECTRE_V2_EIBRS_LFENCE: 1589 case SPECTRE_V2_EIBRS: 1590 if (boot_cpu_has_bug(X86_BUG_EIBRS_PBRSB)) { 1591 setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT_LITE); 1592 pr_info("Spectre v2 / PBRSB-eIBRS: Retire a single CALL on VMEXIT\n"); 1593 } 1594 return; 1595 1596 case SPECTRE_V2_EIBRS_RETPOLINE: 1597 case SPECTRE_V2_RETPOLINE: 1598 case SPECTRE_V2_LFENCE: 1599 case SPECTRE_V2_IBRS: 1600 setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT); 1601 pr_info("Spectre v2 / SpectreRSB : Filling RSB on VMEXIT\n"); 1602 return; 1603 } 1604 1605 pr_warn_once("Unknown Spectre v2 mode, disabling RSB mitigation at VM exit"); 1606 dump_stack(); 1607 } 1608 1609 /* 1610 * Set BHI_DIS_S to prevent indirect branches in kernel to be influenced by 1611 * branch history in userspace. Not needed if BHI_NO is set. 1612 */ 1613 static bool __init spec_ctrl_bhi_dis(void) 1614 { 1615 if (!boot_cpu_has(X86_FEATURE_BHI_CTRL)) 1616 return false; 1617 1618 x86_spec_ctrl_base |= SPEC_CTRL_BHI_DIS_S; 1619 update_spec_ctrl(x86_spec_ctrl_base); 1620 setup_force_cpu_cap(X86_FEATURE_CLEAR_BHB_HW); 1621 1622 return true; 1623 } 1624 1625 enum bhi_mitigations { 1626 BHI_MITIGATION_OFF, 1627 BHI_MITIGATION_ON, 1628 BHI_MITIGATION_VMEXIT_ONLY, 1629 }; 1630 1631 static enum bhi_mitigations bhi_mitigation __ro_after_init = 1632 IS_ENABLED(CONFIG_MITIGATION_SPECTRE_BHI) ? BHI_MITIGATION_ON : BHI_MITIGATION_OFF; 1633 1634 static int __init spectre_bhi_parse_cmdline(char *str) 1635 { 1636 if (!str) 1637 return -EINVAL; 1638 1639 if (!strcmp(str, "off")) 1640 bhi_mitigation = BHI_MITIGATION_OFF; 1641 else if (!strcmp(str, "on")) 1642 bhi_mitigation = BHI_MITIGATION_ON; 1643 else if (!strcmp(str, "vmexit")) 1644 bhi_mitigation = BHI_MITIGATION_VMEXIT_ONLY; 1645 else 1646 pr_err("Ignoring unknown spectre_bhi option (%s)", str); 1647 1648 return 0; 1649 } 1650 early_param("spectre_bhi", spectre_bhi_parse_cmdline); 1651 1652 static void __init bhi_select_mitigation(void) 1653 { 1654 if (bhi_mitigation == BHI_MITIGATION_OFF) 1655 return; 1656 1657 /* Retpoline mitigates against BHI unless the CPU has RRSBA behavior */ 1658 if (boot_cpu_has(X86_FEATURE_RETPOLINE) && 1659 !boot_cpu_has(X86_FEATURE_RETPOLINE_LFENCE)) { 1660 spec_ctrl_disable_kernel_rrsba(); 1661 if (rrsba_disabled) 1662 return; 1663 } 1664 1665 /* Mitigate in hardware if supported */ 1666 if (spec_ctrl_bhi_dis()) 1667 return; 1668 1669 if (!IS_ENABLED(CONFIG_X86_64)) 1670 return; 1671 1672 if (bhi_mitigation == BHI_MITIGATION_VMEXIT_ONLY) { 1673 pr_info("Spectre BHI mitigation: SW BHB clearing on VM exit only\n"); 1674 setup_force_cpu_cap(X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT); 1675 return; 1676 } 1677 1678 pr_info("Spectre BHI mitigation: SW BHB clearing on syscall and VM exit\n"); 1679 setup_force_cpu_cap(X86_FEATURE_CLEAR_BHB_LOOP); 1680 setup_force_cpu_cap(X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT); 1681 } 1682 1683 static void __init spectre_v2_select_mitigation(void) 1684 { 1685 enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline(); 1686 enum spectre_v2_mitigation mode = SPECTRE_V2_NONE; 1687 1688 /* 1689 * If the CPU is not affected and the command line mode is NONE or AUTO 1690 * then nothing to do. 1691 */ 1692 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2) && 1693 (cmd == SPECTRE_V2_CMD_NONE || cmd == SPECTRE_V2_CMD_AUTO)) 1694 return; 1695 1696 switch (cmd) { 1697 case SPECTRE_V2_CMD_NONE: 1698 return; 1699 1700 case SPECTRE_V2_CMD_FORCE: 1701 case SPECTRE_V2_CMD_AUTO: 1702 if (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) { 1703 mode = SPECTRE_V2_EIBRS; 1704 break; 1705 } 1706 1707 if (IS_ENABLED(CONFIG_MITIGATION_IBRS_ENTRY) && 1708 boot_cpu_has_bug(X86_BUG_RETBLEED) && 1709 retbleed_cmd != RETBLEED_CMD_OFF && 1710 retbleed_cmd != RETBLEED_CMD_STUFF && 1711 boot_cpu_has(X86_FEATURE_IBRS) && 1712 boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) { 1713 mode = SPECTRE_V2_IBRS; 1714 break; 1715 } 1716 1717 mode = spectre_v2_select_retpoline(); 1718 break; 1719 1720 case SPECTRE_V2_CMD_RETPOLINE_LFENCE: 1721 pr_err(SPECTRE_V2_LFENCE_MSG); 1722 mode = SPECTRE_V2_LFENCE; 1723 break; 1724 1725 case SPECTRE_V2_CMD_RETPOLINE_GENERIC: 1726 mode = SPECTRE_V2_RETPOLINE; 1727 break; 1728 1729 case SPECTRE_V2_CMD_RETPOLINE: 1730 mode = spectre_v2_select_retpoline(); 1731 break; 1732 1733 case SPECTRE_V2_CMD_IBRS: 1734 mode = SPECTRE_V2_IBRS; 1735 break; 1736 1737 case SPECTRE_V2_CMD_EIBRS: 1738 mode = SPECTRE_V2_EIBRS; 1739 break; 1740 1741 case SPECTRE_V2_CMD_EIBRS_LFENCE: 1742 mode = SPECTRE_V2_EIBRS_LFENCE; 1743 break; 1744 1745 case SPECTRE_V2_CMD_EIBRS_RETPOLINE: 1746 mode = SPECTRE_V2_EIBRS_RETPOLINE; 1747 break; 1748 } 1749 1750 if (mode == SPECTRE_V2_EIBRS && unprivileged_ebpf_enabled()) 1751 pr_err(SPECTRE_V2_EIBRS_EBPF_MSG); 1752 1753 if (spectre_v2_in_ibrs_mode(mode)) { 1754 if (boot_cpu_has(X86_FEATURE_AUTOIBRS)) { 1755 msr_set_bit(MSR_EFER, _EFER_AUTOIBRS); 1756 } else { 1757 x86_spec_ctrl_base |= SPEC_CTRL_IBRS; 1758 update_spec_ctrl(x86_spec_ctrl_base); 1759 } 1760 } 1761 1762 switch (mode) { 1763 case SPECTRE_V2_NONE: 1764 case SPECTRE_V2_EIBRS: 1765 break; 1766 1767 case SPECTRE_V2_IBRS: 1768 setup_force_cpu_cap(X86_FEATURE_KERNEL_IBRS); 1769 if (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) 1770 pr_warn(SPECTRE_V2_IBRS_PERF_MSG); 1771 break; 1772 1773 case SPECTRE_V2_LFENCE: 1774 case SPECTRE_V2_EIBRS_LFENCE: 1775 setup_force_cpu_cap(X86_FEATURE_RETPOLINE_LFENCE); 1776 fallthrough; 1777 1778 case SPECTRE_V2_RETPOLINE: 1779 case SPECTRE_V2_EIBRS_RETPOLINE: 1780 setup_force_cpu_cap(X86_FEATURE_RETPOLINE); 1781 break; 1782 } 1783 1784 /* 1785 * Disable alternate RSB predictions in kernel when indirect CALLs and 1786 * JMPs gets protection against BHI and Intramode-BTI, but RET 1787 * prediction from a non-RSB predictor is still a risk. 1788 */ 1789 if (mode == SPECTRE_V2_EIBRS_LFENCE || 1790 mode == SPECTRE_V2_EIBRS_RETPOLINE || 1791 mode == SPECTRE_V2_RETPOLINE) 1792 spec_ctrl_disable_kernel_rrsba(); 1793 1794 if (boot_cpu_has(X86_BUG_BHI)) 1795 bhi_select_mitigation(); 1796 1797 spectre_v2_enabled = mode; 1798 pr_info("%s\n", spectre_v2_strings[mode]); 1799 1800 /* 1801 * If Spectre v2 protection has been enabled, fill the RSB during a 1802 * context switch. In general there are two types of RSB attacks 1803 * across context switches, for which the CALLs/RETs may be unbalanced. 1804 * 1805 * 1) RSB underflow 1806 * 1807 * Some Intel parts have "bottomless RSB". When the RSB is empty, 1808 * speculated return targets may come from the branch predictor, 1809 * which could have a user-poisoned BTB or BHB entry. 1810 * 1811 * AMD has it even worse: *all* returns are speculated from the BTB, 1812 * regardless of the state of the RSB. 1813 * 1814 * When IBRS or eIBRS is enabled, the "user -> kernel" attack 1815 * scenario is mitigated by the IBRS branch prediction isolation 1816 * properties, so the RSB buffer filling wouldn't be necessary to 1817 * protect against this type of attack. 1818 * 1819 * The "user -> user" attack scenario is mitigated by RSB filling. 1820 * 1821 * 2) Poisoned RSB entry 1822 * 1823 * If the 'next' in-kernel return stack is shorter than 'prev', 1824 * 'next' could be tricked into speculating with a user-poisoned RSB 1825 * entry. 1826 * 1827 * The "user -> kernel" attack scenario is mitigated by SMEP and 1828 * eIBRS. 1829 * 1830 * The "user -> user" scenario, also known as SpectreBHB, requires 1831 * RSB clearing. 1832 * 1833 * So to mitigate all cases, unconditionally fill RSB on context 1834 * switches. 1835 * 1836 * FIXME: Is this pointless for retbleed-affected AMD? 1837 */ 1838 setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW); 1839 pr_info("Spectre v2 / SpectreRSB mitigation: Filling RSB on context switch\n"); 1840 1841 spectre_v2_determine_rsb_fill_type_at_vmexit(mode); 1842 1843 /* 1844 * Retpoline protects the kernel, but doesn't protect firmware. IBRS 1845 * and Enhanced IBRS protect firmware too, so enable IBRS around 1846 * firmware calls only when IBRS / Enhanced / Automatic IBRS aren't 1847 * otherwise enabled. 1848 * 1849 * Use "mode" to check Enhanced IBRS instead of boot_cpu_has(), because 1850 * the user might select retpoline on the kernel command line and if 1851 * the CPU supports Enhanced IBRS, kernel might un-intentionally not 1852 * enable IBRS around firmware calls. 1853 */ 1854 if (boot_cpu_has_bug(X86_BUG_RETBLEED) && 1855 boot_cpu_has(X86_FEATURE_IBPB) && 1856 (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || 1857 boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)) { 1858 1859 if (retbleed_cmd != RETBLEED_CMD_IBPB) { 1860 setup_force_cpu_cap(X86_FEATURE_USE_IBPB_FW); 1861 pr_info("Enabling Speculation Barrier for firmware calls\n"); 1862 } 1863 1864 } else if (boot_cpu_has(X86_FEATURE_IBRS) && !spectre_v2_in_ibrs_mode(mode)) { 1865 setup_force_cpu_cap(X86_FEATURE_USE_IBRS_FW); 1866 pr_info("Enabling Restricted Speculation for firmware calls\n"); 1867 } 1868 1869 /* Set up IBPB and STIBP depending on the general spectre V2 command */ 1870 spectre_v2_cmd = cmd; 1871 } 1872 1873 static void update_stibp_msr(void * __unused) 1874 { 1875 u64 val = spec_ctrl_current() | (x86_spec_ctrl_base & SPEC_CTRL_STIBP); 1876 update_spec_ctrl(val); 1877 } 1878 1879 /* Update x86_spec_ctrl_base in case SMT state changed. */ 1880 static void update_stibp_strict(void) 1881 { 1882 u64 mask = x86_spec_ctrl_base & ~SPEC_CTRL_STIBP; 1883 1884 if (sched_smt_active()) 1885 mask |= SPEC_CTRL_STIBP; 1886 1887 if (mask == x86_spec_ctrl_base) 1888 return; 1889 1890 pr_info("Update user space SMT mitigation: STIBP %s\n", 1891 mask & SPEC_CTRL_STIBP ? "always-on" : "off"); 1892 x86_spec_ctrl_base = mask; 1893 on_each_cpu(update_stibp_msr, NULL, 1); 1894 } 1895 1896 /* Update the static key controlling the evaluation of TIF_SPEC_IB */ 1897 static void update_indir_branch_cond(void) 1898 { 1899 if (sched_smt_active()) 1900 static_branch_enable(&switch_to_cond_stibp); 1901 else 1902 static_branch_disable(&switch_to_cond_stibp); 1903 } 1904 1905 #undef pr_fmt 1906 #define pr_fmt(fmt) fmt 1907 1908 /* Update the static key controlling the MDS CPU buffer clear in idle */ 1909 static void update_mds_branch_idle(void) 1910 { 1911 /* 1912 * Enable the idle clearing if SMT is active on CPUs which are 1913 * affected only by MSBDS and not any other MDS variant. 1914 * 1915 * The other variants cannot be mitigated when SMT is enabled, so 1916 * clearing the buffers on idle just to prevent the Store Buffer 1917 * repartitioning leak would be a window dressing exercise. 1918 */ 1919 if (!boot_cpu_has_bug(X86_BUG_MSBDS_ONLY)) 1920 return; 1921 1922 if (sched_smt_active()) { 1923 static_branch_enable(&mds_idle_clear); 1924 } else if (mmio_mitigation == MMIO_MITIGATION_OFF || 1925 (x86_arch_cap_msr & ARCH_CAP_FBSDP_NO)) { 1926 static_branch_disable(&mds_idle_clear); 1927 } 1928 } 1929 1930 #define MDS_MSG_SMT "MDS CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html for more details.\n" 1931 #define TAA_MSG_SMT "TAA CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/tsx_async_abort.html for more details.\n" 1932 #define MMIO_MSG_SMT "MMIO Stale Data CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/processor_mmio_stale_data.html for more details.\n" 1933 1934 void cpu_bugs_smt_update(void) 1935 { 1936 mutex_lock(&spec_ctrl_mutex); 1937 1938 if (sched_smt_active() && unprivileged_ebpf_enabled() && 1939 spectre_v2_enabled == SPECTRE_V2_EIBRS_LFENCE) 1940 pr_warn_once(SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG); 1941 1942 switch (spectre_v2_user_stibp) { 1943 case SPECTRE_V2_USER_NONE: 1944 break; 1945 case SPECTRE_V2_USER_STRICT: 1946 case SPECTRE_V2_USER_STRICT_PREFERRED: 1947 update_stibp_strict(); 1948 break; 1949 case SPECTRE_V2_USER_PRCTL: 1950 case SPECTRE_V2_USER_SECCOMP: 1951 update_indir_branch_cond(); 1952 break; 1953 } 1954 1955 switch (mds_mitigation) { 1956 case MDS_MITIGATION_FULL: 1957 case MDS_MITIGATION_VMWERV: 1958 if (sched_smt_active() && !boot_cpu_has(X86_BUG_MSBDS_ONLY)) 1959 pr_warn_once(MDS_MSG_SMT); 1960 update_mds_branch_idle(); 1961 break; 1962 case MDS_MITIGATION_OFF: 1963 break; 1964 } 1965 1966 switch (taa_mitigation) { 1967 case TAA_MITIGATION_VERW: 1968 case TAA_MITIGATION_UCODE_NEEDED: 1969 if (sched_smt_active()) 1970 pr_warn_once(TAA_MSG_SMT); 1971 break; 1972 case TAA_MITIGATION_TSX_DISABLED: 1973 case TAA_MITIGATION_OFF: 1974 break; 1975 } 1976 1977 switch (mmio_mitigation) { 1978 case MMIO_MITIGATION_VERW: 1979 case MMIO_MITIGATION_UCODE_NEEDED: 1980 if (sched_smt_active()) 1981 pr_warn_once(MMIO_MSG_SMT); 1982 break; 1983 case MMIO_MITIGATION_OFF: 1984 break; 1985 } 1986 1987 mutex_unlock(&spec_ctrl_mutex); 1988 } 1989 1990 #undef pr_fmt 1991 #define pr_fmt(fmt) "Speculative Store Bypass: " fmt 1992 1993 static enum ssb_mitigation ssb_mode __ro_after_init = SPEC_STORE_BYPASS_NONE; 1994 1995 /* The kernel command line selection */ 1996 enum ssb_mitigation_cmd { 1997 SPEC_STORE_BYPASS_CMD_NONE, 1998 SPEC_STORE_BYPASS_CMD_AUTO, 1999 SPEC_STORE_BYPASS_CMD_ON, 2000 SPEC_STORE_BYPASS_CMD_PRCTL, 2001 SPEC_STORE_BYPASS_CMD_SECCOMP, 2002 }; 2003 2004 static const char * const ssb_strings[] = { 2005 [SPEC_STORE_BYPASS_NONE] = "Vulnerable", 2006 [SPEC_STORE_BYPASS_DISABLE] = "Mitigation: Speculative Store Bypass disabled", 2007 [SPEC_STORE_BYPASS_PRCTL] = "Mitigation: Speculative Store Bypass disabled via prctl", 2008 [SPEC_STORE_BYPASS_SECCOMP] = "Mitigation: Speculative Store Bypass disabled via prctl and seccomp", 2009 }; 2010 2011 static const struct { 2012 const char *option; 2013 enum ssb_mitigation_cmd cmd; 2014 } ssb_mitigation_options[] __initconst = { 2015 { "auto", SPEC_STORE_BYPASS_CMD_AUTO }, /* Platform decides */ 2016 { "on", SPEC_STORE_BYPASS_CMD_ON }, /* Disable Speculative Store Bypass */ 2017 { "off", SPEC_STORE_BYPASS_CMD_NONE }, /* Don't touch Speculative Store Bypass */ 2018 { "prctl", SPEC_STORE_BYPASS_CMD_PRCTL }, /* Disable Speculative Store Bypass via prctl */ 2019 { "seccomp", SPEC_STORE_BYPASS_CMD_SECCOMP }, /* Disable Speculative Store Bypass via prctl and seccomp */ 2020 }; 2021 2022 static enum ssb_mitigation_cmd __init ssb_parse_cmdline(void) 2023 { 2024 enum ssb_mitigation_cmd cmd = SPEC_STORE_BYPASS_CMD_AUTO; 2025 char arg[20]; 2026 int ret, i; 2027 2028 if (cmdline_find_option_bool(boot_command_line, "nospec_store_bypass_disable") || 2029 cpu_mitigations_off()) { 2030 return SPEC_STORE_BYPASS_CMD_NONE; 2031 } else { 2032 ret = cmdline_find_option(boot_command_line, "spec_store_bypass_disable", 2033 arg, sizeof(arg)); 2034 if (ret < 0) 2035 return SPEC_STORE_BYPASS_CMD_AUTO; 2036 2037 for (i = 0; i < ARRAY_SIZE(ssb_mitigation_options); i++) { 2038 if (!match_option(arg, ret, ssb_mitigation_options[i].option)) 2039 continue; 2040 2041 cmd = ssb_mitigation_options[i].cmd; 2042 break; 2043 } 2044 2045 if (i >= ARRAY_SIZE(ssb_mitigation_options)) { 2046 pr_err("unknown option (%s). Switching to AUTO select\n", arg); 2047 return SPEC_STORE_BYPASS_CMD_AUTO; 2048 } 2049 } 2050 2051 return cmd; 2052 } 2053 2054 static enum ssb_mitigation __init __ssb_select_mitigation(void) 2055 { 2056 enum ssb_mitigation mode = SPEC_STORE_BYPASS_NONE; 2057 enum ssb_mitigation_cmd cmd; 2058 2059 if (!boot_cpu_has(X86_FEATURE_SSBD)) 2060 return mode; 2061 2062 cmd = ssb_parse_cmdline(); 2063 if (!boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS) && 2064 (cmd == SPEC_STORE_BYPASS_CMD_NONE || 2065 cmd == SPEC_STORE_BYPASS_CMD_AUTO)) 2066 return mode; 2067 2068 switch (cmd) { 2069 case SPEC_STORE_BYPASS_CMD_SECCOMP: 2070 /* 2071 * Choose prctl+seccomp as the default mode if seccomp is 2072 * enabled. 2073 */ 2074 if (IS_ENABLED(CONFIG_SECCOMP)) 2075 mode = SPEC_STORE_BYPASS_SECCOMP; 2076 else 2077 mode = SPEC_STORE_BYPASS_PRCTL; 2078 break; 2079 case SPEC_STORE_BYPASS_CMD_ON: 2080 mode = SPEC_STORE_BYPASS_DISABLE; 2081 break; 2082 case SPEC_STORE_BYPASS_CMD_AUTO: 2083 case SPEC_STORE_BYPASS_CMD_PRCTL: 2084 mode = SPEC_STORE_BYPASS_PRCTL; 2085 break; 2086 case SPEC_STORE_BYPASS_CMD_NONE: 2087 break; 2088 } 2089 2090 /* 2091 * We have three CPU feature flags that are in play here: 2092 * - X86_BUG_SPEC_STORE_BYPASS - CPU is susceptible. 2093 * - X86_FEATURE_SSBD - CPU is able to turn off speculative store bypass 2094 * - X86_FEATURE_SPEC_STORE_BYPASS_DISABLE - engage the mitigation 2095 */ 2096 if (mode == SPEC_STORE_BYPASS_DISABLE) { 2097 setup_force_cpu_cap(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE); 2098 /* 2099 * Intel uses the SPEC CTRL MSR Bit(2) for this, while AMD may 2100 * use a completely different MSR and bit dependent on family. 2101 */ 2102 if (!static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) && 2103 !static_cpu_has(X86_FEATURE_AMD_SSBD)) { 2104 x86_amd_ssb_disable(); 2105 } else { 2106 x86_spec_ctrl_base |= SPEC_CTRL_SSBD; 2107 update_spec_ctrl(x86_spec_ctrl_base); 2108 } 2109 } 2110 2111 return mode; 2112 } 2113 2114 static void ssb_select_mitigation(void) 2115 { 2116 ssb_mode = __ssb_select_mitigation(); 2117 2118 if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS)) 2119 pr_info("%s\n", ssb_strings[ssb_mode]); 2120 } 2121 2122 #undef pr_fmt 2123 #define pr_fmt(fmt) "Speculation prctl: " fmt 2124 2125 static void task_update_spec_tif(struct task_struct *tsk) 2126 { 2127 /* Force the update of the real TIF bits */ 2128 set_tsk_thread_flag(tsk, TIF_SPEC_FORCE_UPDATE); 2129 2130 /* 2131 * Immediately update the speculation control MSRs for the current 2132 * task, but for a non-current task delay setting the CPU 2133 * mitigation until it is scheduled next. 2134 * 2135 * This can only happen for SECCOMP mitigation. For PRCTL it's 2136 * always the current task. 2137 */ 2138 if (tsk == current) 2139 speculation_ctrl_update_current(); 2140 } 2141 2142 static int l1d_flush_prctl_set(struct task_struct *task, unsigned long ctrl) 2143 { 2144 2145 if (!static_branch_unlikely(&switch_mm_cond_l1d_flush)) 2146 return -EPERM; 2147 2148 switch (ctrl) { 2149 case PR_SPEC_ENABLE: 2150 set_ti_thread_flag(&task->thread_info, TIF_SPEC_L1D_FLUSH); 2151 return 0; 2152 case PR_SPEC_DISABLE: 2153 clear_ti_thread_flag(&task->thread_info, TIF_SPEC_L1D_FLUSH); 2154 return 0; 2155 default: 2156 return -ERANGE; 2157 } 2158 } 2159 2160 static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl) 2161 { 2162 if (ssb_mode != SPEC_STORE_BYPASS_PRCTL && 2163 ssb_mode != SPEC_STORE_BYPASS_SECCOMP) 2164 return -ENXIO; 2165 2166 switch (ctrl) { 2167 case PR_SPEC_ENABLE: 2168 /* If speculation is force disabled, enable is not allowed */ 2169 if (task_spec_ssb_force_disable(task)) 2170 return -EPERM; 2171 task_clear_spec_ssb_disable(task); 2172 task_clear_spec_ssb_noexec(task); 2173 task_update_spec_tif(task); 2174 break; 2175 case PR_SPEC_DISABLE: 2176 task_set_spec_ssb_disable(task); 2177 task_clear_spec_ssb_noexec(task); 2178 task_update_spec_tif(task); 2179 break; 2180 case PR_SPEC_FORCE_DISABLE: 2181 task_set_spec_ssb_disable(task); 2182 task_set_spec_ssb_force_disable(task); 2183 task_clear_spec_ssb_noexec(task); 2184 task_update_spec_tif(task); 2185 break; 2186 case PR_SPEC_DISABLE_NOEXEC: 2187 if (task_spec_ssb_force_disable(task)) 2188 return -EPERM; 2189 task_set_spec_ssb_disable(task); 2190 task_set_spec_ssb_noexec(task); 2191 task_update_spec_tif(task); 2192 break; 2193 default: 2194 return -ERANGE; 2195 } 2196 return 0; 2197 } 2198 2199 static bool is_spec_ib_user_controlled(void) 2200 { 2201 return spectre_v2_user_ibpb == SPECTRE_V2_USER_PRCTL || 2202 spectre_v2_user_ibpb == SPECTRE_V2_USER_SECCOMP || 2203 spectre_v2_user_stibp == SPECTRE_V2_USER_PRCTL || 2204 spectre_v2_user_stibp == SPECTRE_V2_USER_SECCOMP; 2205 } 2206 2207 static int ib_prctl_set(struct task_struct *task, unsigned long ctrl) 2208 { 2209 switch (ctrl) { 2210 case PR_SPEC_ENABLE: 2211 if (spectre_v2_user_ibpb == SPECTRE_V2_USER_NONE && 2212 spectre_v2_user_stibp == SPECTRE_V2_USER_NONE) 2213 return 0; 2214 2215 /* 2216 * With strict mode for both IBPB and STIBP, the instruction 2217 * code paths avoid checking this task flag and instead, 2218 * unconditionally run the instruction. However, STIBP and IBPB 2219 * are independent and either can be set to conditionally 2220 * enabled regardless of the mode of the other. 2221 * 2222 * If either is set to conditional, allow the task flag to be 2223 * updated, unless it was force-disabled by a previous prctl 2224 * call. Currently, this is possible on an AMD CPU which has the 2225 * feature X86_FEATURE_AMD_STIBP_ALWAYS_ON. In this case, if the 2226 * kernel is booted with 'spectre_v2_user=seccomp', then 2227 * spectre_v2_user_ibpb == SPECTRE_V2_USER_SECCOMP and 2228 * spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT_PREFERRED. 2229 */ 2230 if (!is_spec_ib_user_controlled() || 2231 task_spec_ib_force_disable(task)) 2232 return -EPERM; 2233 2234 task_clear_spec_ib_disable(task); 2235 task_update_spec_tif(task); 2236 break; 2237 case PR_SPEC_DISABLE: 2238 case PR_SPEC_FORCE_DISABLE: 2239 /* 2240 * Indirect branch speculation is always allowed when 2241 * mitigation is force disabled. 2242 */ 2243 if (spectre_v2_user_ibpb == SPECTRE_V2_USER_NONE && 2244 spectre_v2_user_stibp == SPECTRE_V2_USER_NONE) 2245 return -EPERM; 2246 2247 if (!is_spec_ib_user_controlled()) 2248 return 0; 2249 2250 task_set_spec_ib_disable(task); 2251 if (ctrl == PR_SPEC_FORCE_DISABLE) 2252 task_set_spec_ib_force_disable(task); 2253 task_update_spec_tif(task); 2254 if (task == current) 2255 indirect_branch_prediction_barrier(); 2256 break; 2257 default: 2258 return -ERANGE; 2259 } 2260 return 0; 2261 } 2262 2263 int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which, 2264 unsigned long ctrl) 2265 { 2266 switch (which) { 2267 case PR_SPEC_STORE_BYPASS: 2268 return ssb_prctl_set(task, ctrl); 2269 case PR_SPEC_INDIRECT_BRANCH: 2270 return ib_prctl_set(task, ctrl); 2271 case PR_SPEC_L1D_FLUSH: 2272 return l1d_flush_prctl_set(task, ctrl); 2273 default: 2274 return -ENODEV; 2275 } 2276 } 2277 2278 #ifdef CONFIG_SECCOMP 2279 void arch_seccomp_spec_mitigate(struct task_struct *task) 2280 { 2281 if (ssb_mode == SPEC_STORE_BYPASS_SECCOMP) 2282 ssb_prctl_set(task, PR_SPEC_FORCE_DISABLE); 2283 if (spectre_v2_user_ibpb == SPECTRE_V2_USER_SECCOMP || 2284 spectre_v2_user_stibp == SPECTRE_V2_USER_SECCOMP) 2285 ib_prctl_set(task, PR_SPEC_FORCE_DISABLE); 2286 } 2287 #endif 2288 2289 static int l1d_flush_prctl_get(struct task_struct *task) 2290 { 2291 if (!static_branch_unlikely(&switch_mm_cond_l1d_flush)) 2292 return PR_SPEC_FORCE_DISABLE; 2293 2294 if (test_ti_thread_flag(&task->thread_info, TIF_SPEC_L1D_FLUSH)) 2295 return PR_SPEC_PRCTL | PR_SPEC_ENABLE; 2296 else 2297 return PR_SPEC_PRCTL | PR_SPEC_DISABLE; 2298 } 2299 2300 static int ssb_prctl_get(struct task_struct *task) 2301 { 2302 switch (ssb_mode) { 2303 case SPEC_STORE_BYPASS_NONE: 2304 if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS)) 2305 return PR_SPEC_ENABLE; 2306 return PR_SPEC_NOT_AFFECTED; 2307 case SPEC_STORE_BYPASS_DISABLE: 2308 return PR_SPEC_DISABLE; 2309 case SPEC_STORE_BYPASS_SECCOMP: 2310 case SPEC_STORE_BYPASS_PRCTL: 2311 if (task_spec_ssb_force_disable(task)) 2312 return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE; 2313 if (task_spec_ssb_noexec(task)) 2314 return PR_SPEC_PRCTL | PR_SPEC_DISABLE_NOEXEC; 2315 if (task_spec_ssb_disable(task)) 2316 return PR_SPEC_PRCTL | PR_SPEC_DISABLE; 2317 return PR_SPEC_PRCTL | PR_SPEC_ENABLE; 2318 } 2319 BUG(); 2320 } 2321 2322 static int ib_prctl_get(struct task_struct *task) 2323 { 2324 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2)) 2325 return PR_SPEC_NOT_AFFECTED; 2326 2327 if (spectre_v2_user_ibpb == SPECTRE_V2_USER_NONE && 2328 spectre_v2_user_stibp == SPECTRE_V2_USER_NONE) 2329 return PR_SPEC_ENABLE; 2330 else if (is_spec_ib_user_controlled()) { 2331 if (task_spec_ib_force_disable(task)) 2332 return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE; 2333 if (task_spec_ib_disable(task)) 2334 return PR_SPEC_PRCTL | PR_SPEC_DISABLE; 2335 return PR_SPEC_PRCTL | PR_SPEC_ENABLE; 2336 } else if (spectre_v2_user_ibpb == SPECTRE_V2_USER_STRICT || 2337 spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT || 2338 spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT_PREFERRED) 2339 return PR_SPEC_DISABLE; 2340 else 2341 return PR_SPEC_NOT_AFFECTED; 2342 } 2343 2344 int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which) 2345 { 2346 switch (which) { 2347 case PR_SPEC_STORE_BYPASS: 2348 return ssb_prctl_get(task); 2349 case PR_SPEC_INDIRECT_BRANCH: 2350 return ib_prctl_get(task); 2351 case PR_SPEC_L1D_FLUSH: 2352 return l1d_flush_prctl_get(task); 2353 default: 2354 return -ENODEV; 2355 } 2356 } 2357 2358 void x86_spec_ctrl_setup_ap(void) 2359 { 2360 if (boot_cpu_has(X86_FEATURE_MSR_SPEC_CTRL)) 2361 update_spec_ctrl(x86_spec_ctrl_base); 2362 2363 if (ssb_mode == SPEC_STORE_BYPASS_DISABLE) 2364 x86_amd_ssb_disable(); 2365 } 2366 2367 bool itlb_multihit_kvm_mitigation; 2368 EXPORT_SYMBOL_GPL(itlb_multihit_kvm_mitigation); 2369 2370 #undef pr_fmt 2371 #define pr_fmt(fmt) "L1TF: " fmt 2372 2373 /* Default mitigation for L1TF-affected CPUs */ 2374 enum l1tf_mitigations l1tf_mitigation __ro_after_init = L1TF_MITIGATION_FLUSH; 2375 #if IS_ENABLED(CONFIG_KVM_INTEL) 2376 EXPORT_SYMBOL_GPL(l1tf_mitigation); 2377 #endif 2378 enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_AUTO; 2379 EXPORT_SYMBOL_GPL(l1tf_vmx_mitigation); 2380 2381 /* 2382 * These CPUs all support 44bits physical address space internally in the 2383 * cache but CPUID can report a smaller number of physical address bits. 2384 * 2385 * The L1TF mitigation uses the top most address bit for the inversion of 2386 * non present PTEs. When the installed memory reaches into the top most 2387 * address bit due to memory holes, which has been observed on machines 2388 * which report 36bits physical address bits and have 32G RAM installed, 2389 * then the mitigation range check in l1tf_select_mitigation() triggers. 2390 * This is a false positive because the mitigation is still possible due to 2391 * the fact that the cache uses 44bit internally. Use the cache bits 2392 * instead of the reported physical bits and adjust them on the affected 2393 * machines to 44bit if the reported bits are less than 44. 2394 */ 2395 static void override_cache_bits(struct cpuinfo_x86 *c) 2396 { 2397 if (c->x86 != 6) 2398 return; 2399 2400 switch (c->x86_vfm) { 2401 case INTEL_NEHALEM: 2402 case INTEL_WESTMERE: 2403 case INTEL_SANDYBRIDGE: 2404 case INTEL_IVYBRIDGE: 2405 case INTEL_HASWELL: 2406 case INTEL_HASWELL_L: 2407 case INTEL_HASWELL_G: 2408 case INTEL_BROADWELL: 2409 case INTEL_BROADWELL_G: 2410 case INTEL_SKYLAKE_L: 2411 case INTEL_SKYLAKE: 2412 case INTEL_KABYLAKE_L: 2413 case INTEL_KABYLAKE: 2414 if (c->x86_cache_bits < 44) 2415 c->x86_cache_bits = 44; 2416 break; 2417 } 2418 } 2419 2420 static void __init l1tf_select_mitigation(void) 2421 { 2422 u64 half_pa; 2423 2424 if (!boot_cpu_has_bug(X86_BUG_L1TF)) 2425 return; 2426 2427 if (cpu_mitigations_off()) 2428 l1tf_mitigation = L1TF_MITIGATION_OFF; 2429 else if (cpu_mitigations_auto_nosmt()) 2430 l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT; 2431 2432 override_cache_bits(&boot_cpu_data); 2433 2434 switch (l1tf_mitigation) { 2435 case L1TF_MITIGATION_OFF: 2436 case L1TF_MITIGATION_FLUSH_NOWARN: 2437 case L1TF_MITIGATION_FLUSH: 2438 break; 2439 case L1TF_MITIGATION_FLUSH_NOSMT: 2440 case L1TF_MITIGATION_FULL: 2441 cpu_smt_disable(false); 2442 break; 2443 case L1TF_MITIGATION_FULL_FORCE: 2444 cpu_smt_disable(true); 2445 break; 2446 } 2447 2448 #if CONFIG_PGTABLE_LEVELS == 2 2449 pr_warn("Kernel not compiled for PAE. No mitigation for L1TF\n"); 2450 return; 2451 #endif 2452 2453 half_pa = (u64)l1tf_pfn_limit() << PAGE_SHIFT; 2454 if (l1tf_mitigation != L1TF_MITIGATION_OFF && 2455 e820__mapped_any(half_pa, ULLONG_MAX - half_pa, E820_TYPE_RAM)) { 2456 pr_warn("System has more than MAX_PA/2 memory. L1TF mitigation not effective.\n"); 2457 pr_info("You may make it effective by booting the kernel with mem=%llu parameter.\n", 2458 half_pa); 2459 pr_info("However, doing so will make a part of your RAM unusable.\n"); 2460 pr_info("Reading https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html might help you decide.\n"); 2461 return; 2462 } 2463 2464 setup_force_cpu_cap(X86_FEATURE_L1TF_PTEINV); 2465 } 2466 2467 static int __init l1tf_cmdline(char *str) 2468 { 2469 if (!boot_cpu_has_bug(X86_BUG_L1TF)) 2470 return 0; 2471 2472 if (!str) 2473 return -EINVAL; 2474 2475 if (!strcmp(str, "off")) 2476 l1tf_mitigation = L1TF_MITIGATION_OFF; 2477 else if (!strcmp(str, "flush,nowarn")) 2478 l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOWARN; 2479 else if (!strcmp(str, "flush")) 2480 l1tf_mitigation = L1TF_MITIGATION_FLUSH; 2481 else if (!strcmp(str, "flush,nosmt")) 2482 l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT; 2483 else if (!strcmp(str, "full")) 2484 l1tf_mitigation = L1TF_MITIGATION_FULL; 2485 else if (!strcmp(str, "full,force")) 2486 l1tf_mitigation = L1TF_MITIGATION_FULL_FORCE; 2487 2488 return 0; 2489 } 2490 early_param("l1tf", l1tf_cmdline); 2491 2492 #undef pr_fmt 2493 #define pr_fmt(fmt) "Speculative Return Stack Overflow: " fmt 2494 2495 enum srso_mitigation { 2496 SRSO_MITIGATION_NONE, 2497 SRSO_MITIGATION_UCODE_NEEDED, 2498 SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED, 2499 SRSO_MITIGATION_MICROCODE, 2500 SRSO_MITIGATION_SAFE_RET, 2501 SRSO_MITIGATION_IBPB, 2502 SRSO_MITIGATION_IBPB_ON_VMEXIT, 2503 }; 2504 2505 enum srso_mitigation_cmd { 2506 SRSO_CMD_OFF, 2507 SRSO_CMD_MICROCODE, 2508 SRSO_CMD_SAFE_RET, 2509 SRSO_CMD_IBPB, 2510 SRSO_CMD_IBPB_ON_VMEXIT, 2511 }; 2512 2513 static const char * const srso_strings[] = { 2514 [SRSO_MITIGATION_NONE] = "Vulnerable", 2515 [SRSO_MITIGATION_UCODE_NEEDED] = "Vulnerable: No microcode", 2516 [SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED] = "Vulnerable: Safe RET, no microcode", 2517 [SRSO_MITIGATION_MICROCODE] = "Vulnerable: Microcode, no safe RET", 2518 [SRSO_MITIGATION_SAFE_RET] = "Mitigation: Safe RET", 2519 [SRSO_MITIGATION_IBPB] = "Mitigation: IBPB", 2520 [SRSO_MITIGATION_IBPB_ON_VMEXIT] = "Mitigation: IBPB on VMEXIT only" 2521 }; 2522 2523 static enum srso_mitigation srso_mitigation __ro_after_init = SRSO_MITIGATION_NONE; 2524 static enum srso_mitigation_cmd srso_cmd __ro_after_init = SRSO_CMD_SAFE_RET; 2525 2526 static int __init srso_parse_cmdline(char *str) 2527 { 2528 if (!str) 2529 return -EINVAL; 2530 2531 if (!strcmp(str, "off")) 2532 srso_cmd = SRSO_CMD_OFF; 2533 else if (!strcmp(str, "microcode")) 2534 srso_cmd = SRSO_CMD_MICROCODE; 2535 else if (!strcmp(str, "safe-ret")) 2536 srso_cmd = SRSO_CMD_SAFE_RET; 2537 else if (!strcmp(str, "ibpb")) 2538 srso_cmd = SRSO_CMD_IBPB; 2539 else if (!strcmp(str, "ibpb-vmexit")) 2540 srso_cmd = SRSO_CMD_IBPB_ON_VMEXIT; 2541 else 2542 pr_err("Ignoring unknown SRSO option (%s).", str); 2543 2544 return 0; 2545 } 2546 early_param("spec_rstack_overflow", srso_parse_cmdline); 2547 2548 #define SRSO_NOTICE "WARNING: See https://kernel.org/doc/html/latest/admin-guide/hw-vuln/srso.html for mitigation options." 2549 2550 static void __init srso_select_mitigation(void) 2551 { 2552 bool has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE); 2553 2554 if (cpu_mitigations_off()) 2555 return; 2556 2557 if (!boot_cpu_has_bug(X86_BUG_SRSO)) { 2558 if (boot_cpu_has(X86_FEATURE_SBPB)) 2559 x86_pred_cmd = PRED_CMD_SBPB; 2560 return; 2561 } 2562 2563 if (has_microcode) { 2564 /* 2565 * Zen1/2 with SMT off aren't vulnerable after the right 2566 * IBPB microcode has been applied. 2567 * 2568 * Zen1/2 don't have SBPB, no need to try to enable it here. 2569 */ 2570 if (boot_cpu_data.x86 < 0x19 && !cpu_smt_possible()) { 2571 setup_force_cpu_cap(X86_FEATURE_SRSO_NO); 2572 return; 2573 } 2574 2575 if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) { 2576 srso_mitigation = SRSO_MITIGATION_IBPB; 2577 goto out; 2578 } 2579 } else { 2580 pr_warn("IBPB-extending microcode not applied!\n"); 2581 pr_warn(SRSO_NOTICE); 2582 2583 /* may be overwritten by SRSO_CMD_SAFE_RET below */ 2584 srso_mitigation = SRSO_MITIGATION_UCODE_NEEDED; 2585 } 2586 2587 switch (srso_cmd) { 2588 case SRSO_CMD_OFF: 2589 if (boot_cpu_has(X86_FEATURE_SBPB)) 2590 x86_pred_cmd = PRED_CMD_SBPB; 2591 return; 2592 2593 case SRSO_CMD_MICROCODE: 2594 if (has_microcode) { 2595 srso_mitigation = SRSO_MITIGATION_MICROCODE; 2596 pr_warn(SRSO_NOTICE); 2597 } 2598 break; 2599 2600 case SRSO_CMD_SAFE_RET: 2601 if (IS_ENABLED(CONFIG_MITIGATION_SRSO)) { 2602 /* 2603 * Enable the return thunk for generated code 2604 * like ftrace, static_call, etc. 2605 */ 2606 setup_force_cpu_cap(X86_FEATURE_RETHUNK); 2607 setup_force_cpu_cap(X86_FEATURE_UNRET); 2608 2609 if (boot_cpu_data.x86 == 0x19) { 2610 setup_force_cpu_cap(X86_FEATURE_SRSO_ALIAS); 2611 x86_return_thunk = srso_alias_return_thunk; 2612 } else { 2613 setup_force_cpu_cap(X86_FEATURE_SRSO); 2614 x86_return_thunk = srso_return_thunk; 2615 } 2616 if (has_microcode) 2617 srso_mitigation = SRSO_MITIGATION_SAFE_RET; 2618 else 2619 srso_mitigation = SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED; 2620 } else { 2621 pr_err("WARNING: kernel not compiled with MITIGATION_SRSO.\n"); 2622 } 2623 break; 2624 2625 case SRSO_CMD_IBPB: 2626 if (IS_ENABLED(CONFIG_MITIGATION_IBPB_ENTRY)) { 2627 if (has_microcode) { 2628 setup_force_cpu_cap(X86_FEATURE_ENTRY_IBPB); 2629 srso_mitigation = SRSO_MITIGATION_IBPB; 2630 } 2631 } else { 2632 pr_err("WARNING: kernel not compiled with MITIGATION_IBPB_ENTRY.\n"); 2633 } 2634 break; 2635 2636 case SRSO_CMD_IBPB_ON_VMEXIT: 2637 if (IS_ENABLED(CONFIG_MITIGATION_SRSO)) { 2638 if (!boot_cpu_has(X86_FEATURE_ENTRY_IBPB) && has_microcode) { 2639 setup_force_cpu_cap(X86_FEATURE_IBPB_ON_VMEXIT); 2640 srso_mitigation = SRSO_MITIGATION_IBPB_ON_VMEXIT; 2641 } 2642 } else { 2643 pr_err("WARNING: kernel not compiled with MITIGATION_SRSO.\n"); 2644 } 2645 break; 2646 } 2647 2648 out: 2649 pr_info("%s\n", srso_strings[srso_mitigation]); 2650 } 2651 2652 #undef pr_fmt 2653 #define pr_fmt(fmt) fmt 2654 2655 #ifdef CONFIG_SYSFS 2656 2657 #define L1TF_DEFAULT_MSG "Mitigation: PTE Inversion" 2658 2659 #if IS_ENABLED(CONFIG_KVM_INTEL) 2660 static const char * const l1tf_vmx_states[] = { 2661 [VMENTER_L1D_FLUSH_AUTO] = "auto", 2662 [VMENTER_L1D_FLUSH_NEVER] = "vulnerable", 2663 [VMENTER_L1D_FLUSH_COND] = "conditional cache flushes", 2664 [VMENTER_L1D_FLUSH_ALWAYS] = "cache flushes", 2665 [VMENTER_L1D_FLUSH_EPT_DISABLED] = "EPT disabled", 2666 [VMENTER_L1D_FLUSH_NOT_REQUIRED] = "flush not necessary" 2667 }; 2668 2669 static ssize_t l1tf_show_state(char *buf) 2670 { 2671 if (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_AUTO) 2672 return sysfs_emit(buf, "%s\n", L1TF_DEFAULT_MSG); 2673 2674 if (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_EPT_DISABLED || 2675 (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_NEVER && 2676 sched_smt_active())) { 2677 return sysfs_emit(buf, "%s; VMX: %s\n", L1TF_DEFAULT_MSG, 2678 l1tf_vmx_states[l1tf_vmx_mitigation]); 2679 } 2680 2681 return sysfs_emit(buf, "%s; VMX: %s, SMT %s\n", L1TF_DEFAULT_MSG, 2682 l1tf_vmx_states[l1tf_vmx_mitigation], 2683 sched_smt_active() ? "vulnerable" : "disabled"); 2684 } 2685 2686 static ssize_t itlb_multihit_show_state(char *buf) 2687 { 2688 if (!boot_cpu_has(X86_FEATURE_MSR_IA32_FEAT_CTL) || 2689 !boot_cpu_has(X86_FEATURE_VMX)) 2690 return sysfs_emit(buf, "KVM: Mitigation: VMX unsupported\n"); 2691 else if (!(cr4_read_shadow() & X86_CR4_VMXE)) 2692 return sysfs_emit(buf, "KVM: Mitigation: VMX disabled\n"); 2693 else if (itlb_multihit_kvm_mitigation) 2694 return sysfs_emit(buf, "KVM: Mitigation: Split huge pages\n"); 2695 else 2696 return sysfs_emit(buf, "KVM: Vulnerable\n"); 2697 } 2698 #else 2699 static ssize_t l1tf_show_state(char *buf) 2700 { 2701 return sysfs_emit(buf, "%s\n", L1TF_DEFAULT_MSG); 2702 } 2703 2704 static ssize_t itlb_multihit_show_state(char *buf) 2705 { 2706 return sysfs_emit(buf, "Processor vulnerable\n"); 2707 } 2708 #endif 2709 2710 static ssize_t mds_show_state(char *buf) 2711 { 2712 if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) { 2713 return sysfs_emit(buf, "%s; SMT Host state unknown\n", 2714 mds_strings[mds_mitigation]); 2715 } 2716 2717 if (boot_cpu_has(X86_BUG_MSBDS_ONLY)) { 2718 return sysfs_emit(buf, "%s; SMT %s\n", mds_strings[mds_mitigation], 2719 (mds_mitigation == MDS_MITIGATION_OFF ? "vulnerable" : 2720 sched_smt_active() ? "mitigated" : "disabled")); 2721 } 2722 2723 return sysfs_emit(buf, "%s; SMT %s\n", mds_strings[mds_mitigation], 2724 sched_smt_active() ? "vulnerable" : "disabled"); 2725 } 2726 2727 static ssize_t tsx_async_abort_show_state(char *buf) 2728 { 2729 if ((taa_mitigation == TAA_MITIGATION_TSX_DISABLED) || 2730 (taa_mitigation == TAA_MITIGATION_OFF)) 2731 return sysfs_emit(buf, "%s\n", taa_strings[taa_mitigation]); 2732 2733 if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) { 2734 return sysfs_emit(buf, "%s; SMT Host state unknown\n", 2735 taa_strings[taa_mitigation]); 2736 } 2737 2738 return sysfs_emit(buf, "%s; SMT %s\n", taa_strings[taa_mitigation], 2739 sched_smt_active() ? "vulnerable" : "disabled"); 2740 } 2741 2742 static ssize_t mmio_stale_data_show_state(char *buf) 2743 { 2744 if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN)) 2745 return sysfs_emit(buf, "Unknown: No mitigations\n"); 2746 2747 if (mmio_mitigation == MMIO_MITIGATION_OFF) 2748 return sysfs_emit(buf, "%s\n", mmio_strings[mmio_mitigation]); 2749 2750 if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) { 2751 return sysfs_emit(buf, "%s; SMT Host state unknown\n", 2752 mmio_strings[mmio_mitigation]); 2753 } 2754 2755 return sysfs_emit(buf, "%s; SMT %s\n", mmio_strings[mmio_mitigation], 2756 sched_smt_active() ? "vulnerable" : "disabled"); 2757 } 2758 2759 static ssize_t rfds_show_state(char *buf) 2760 { 2761 return sysfs_emit(buf, "%s\n", rfds_strings[rfds_mitigation]); 2762 } 2763 2764 static char *stibp_state(void) 2765 { 2766 if (spectre_v2_in_eibrs_mode(spectre_v2_enabled) && 2767 !boot_cpu_has(X86_FEATURE_AUTOIBRS)) 2768 return ""; 2769 2770 switch (spectre_v2_user_stibp) { 2771 case SPECTRE_V2_USER_NONE: 2772 return "; STIBP: disabled"; 2773 case SPECTRE_V2_USER_STRICT: 2774 return "; STIBP: forced"; 2775 case SPECTRE_V2_USER_STRICT_PREFERRED: 2776 return "; STIBP: always-on"; 2777 case SPECTRE_V2_USER_PRCTL: 2778 case SPECTRE_V2_USER_SECCOMP: 2779 if (static_key_enabled(&switch_to_cond_stibp)) 2780 return "; STIBP: conditional"; 2781 } 2782 return ""; 2783 } 2784 2785 static char *ibpb_state(void) 2786 { 2787 if (boot_cpu_has(X86_FEATURE_IBPB)) { 2788 if (static_key_enabled(&switch_mm_always_ibpb)) 2789 return "; IBPB: always-on"; 2790 if (static_key_enabled(&switch_mm_cond_ibpb)) 2791 return "; IBPB: conditional"; 2792 return "; IBPB: disabled"; 2793 } 2794 return ""; 2795 } 2796 2797 static char *pbrsb_eibrs_state(void) 2798 { 2799 if (boot_cpu_has_bug(X86_BUG_EIBRS_PBRSB)) { 2800 if (boot_cpu_has(X86_FEATURE_RSB_VMEXIT_LITE) || 2801 boot_cpu_has(X86_FEATURE_RSB_VMEXIT)) 2802 return "; PBRSB-eIBRS: SW sequence"; 2803 else 2804 return "; PBRSB-eIBRS: Vulnerable"; 2805 } else { 2806 return "; PBRSB-eIBRS: Not affected"; 2807 } 2808 } 2809 2810 static const char *spectre_bhi_state(void) 2811 { 2812 if (!boot_cpu_has_bug(X86_BUG_BHI)) 2813 return "; BHI: Not affected"; 2814 else if (boot_cpu_has(X86_FEATURE_CLEAR_BHB_HW)) 2815 return "; BHI: BHI_DIS_S"; 2816 else if (boot_cpu_has(X86_FEATURE_CLEAR_BHB_LOOP)) 2817 return "; BHI: SW loop, KVM: SW loop"; 2818 else if (boot_cpu_has(X86_FEATURE_RETPOLINE) && 2819 !boot_cpu_has(X86_FEATURE_RETPOLINE_LFENCE) && 2820 rrsba_disabled) 2821 return "; BHI: Retpoline"; 2822 else if (boot_cpu_has(X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT)) 2823 return "; BHI: Vulnerable, KVM: SW loop"; 2824 2825 return "; BHI: Vulnerable"; 2826 } 2827 2828 static ssize_t spectre_v2_show_state(char *buf) 2829 { 2830 if (spectre_v2_enabled == SPECTRE_V2_LFENCE) 2831 return sysfs_emit(buf, "Vulnerable: LFENCE\n"); 2832 2833 if (spectre_v2_enabled == SPECTRE_V2_EIBRS && unprivileged_ebpf_enabled()) 2834 return sysfs_emit(buf, "Vulnerable: eIBRS with unprivileged eBPF\n"); 2835 2836 if (sched_smt_active() && unprivileged_ebpf_enabled() && 2837 spectre_v2_enabled == SPECTRE_V2_EIBRS_LFENCE) 2838 return sysfs_emit(buf, "Vulnerable: eIBRS+LFENCE with unprivileged eBPF and SMT\n"); 2839 2840 return sysfs_emit(buf, "%s%s%s%s%s%s%s%s\n", 2841 spectre_v2_strings[spectre_v2_enabled], 2842 ibpb_state(), 2843 boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? "; IBRS_FW" : "", 2844 stibp_state(), 2845 boot_cpu_has(X86_FEATURE_RSB_CTXSW) ? "; RSB filling" : "", 2846 pbrsb_eibrs_state(), 2847 spectre_bhi_state(), 2848 /* this should always be at the end */ 2849 spectre_v2_module_string()); 2850 } 2851 2852 static ssize_t srbds_show_state(char *buf) 2853 { 2854 return sysfs_emit(buf, "%s\n", srbds_strings[srbds_mitigation]); 2855 } 2856 2857 static ssize_t retbleed_show_state(char *buf) 2858 { 2859 if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET || 2860 retbleed_mitigation == RETBLEED_MITIGATION_IBPB) { 2861 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD && 2862 boot_cpu_data.x86_vendor != X86_VENDOR_HYGON) 2863 return sysfs_emit(buf, "Vulnerable: untrained return thunk / IBPB on non-AMD based uarch\n"); 2864 2865 return sysfs_emit(buf, "%s; SMT %s\n", retbleed_strings[retbleed_mitigation], 2866 !sched_smt_active() ? "disabled" : 2867 spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT || 2868 spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT_PREFERRED ? 2869 "enabled with STIBP protection" : "vulnerable"); 2870 } 2871 2872 return sysfs_emit(buf, "%s\n", retbleed_strings[retbleed_mitigation]); 2873 } 2874 2875 static ssize_t srso_show_state(char *buf) 2876 { 2877 if (boot_cpu_has(X86_FEATURE_SRSO_NO)) 2878 return sysfs_emit(buf, "Mitigation: SMT disabled\n"); 2879 2880 return sysfs_emit(buf, "%s\n", srso_strings[srso_mitigation]); 2881 } 2882 2883 static ssize_t gds_show_state(char *buf) 2884 { 2885 return sysfs_emit(buf, "%s\n", gds_strings[gds_mitigation]); 2886 } 2887 2888 static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr, 2889 char *buf, unsigned int bug) 2890 { 2891 if (!boot_cpu_has_bug(bug)) 2892 return sysfs_emit(buf, "Not affected\n"); 2893 2894 switch (bug) { 2895 case X86_BUG_CPU_MELTDOWN: 2896 if (boot_cpu_has(X86_FEATURE_PTI)) 2897 return sysfs_emit(buf, "Mitigation: PTI\n"); 2898 2899 if (hypervisor_is_type(X86_HYPER_XEN_PV)) 2900 return sysfs_emit(buf, "Unknown (XEN PV detected, hypervisor mitigation required)\n"); 2901 2902 break; 2903 2904 case X86_BUG_SPECTRE_V1: 2905 return sysfs_emit(buf, "%s\n", spectre_v1_strings[spectre_v1_mitigation]); 2906 2907 case X86_BUG_SPECTRE_V2: 2908 return spectre_v2_show_state(buf); 2909 2910 case X86_BUG_SPEC_STORE_BYPASS: 2911 return sysfs_emit(buf, "%s\n", ssb_strings[ssb_mode]); 2912 2913 case X86_BUG_L1TF: 2914 if (boot_cpu_has(X86_FEATURE_L1TF_PTEINV)) 2915 return l1tf_show_state(buf); 2916 break; 2917 2918 case X86_BUG_MDS: 2919 return mds_show_state(buf); 2920 2921 case X86_BUG_TAA: 2922 return tsx_async_abort_show_state(buf); 2923 2924 case X86_BUG_ITLB_MULTIHIT: 2925 return itlb_multihit_show_state(buf); 2926 2927 case X86_BUG_SRBDS: 2928 return srbds_show_state(buf); 2929 2930 case X86_BUG_MMIO_STALE_DATA: 2931 case X86_BUG_MMIO_UNKNOWN: 2932 return mmio_stale_data_show_state(buf); 2933 2934 case X86_BUG_RETBLEED: 2935 return retbleed_show_state(buf); 2936 2937 case X86_BUG_SRSO: 2938 return srso_show_state(buf); 2939 2940 case X86_BUG_GDS: 2941 return gds_show_state(buf); 2942 2943 case X86_BUG_RFDS: 2944 return rfds_show_state(buf); 2945 2946 default: 2947 break; 2948 } 2949 2950 return sysfs_emit(buf, "Vulnerable\n"); 2951 } 2952 2953 ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf) 2954 { 2955 return cpu_show_common(dev, attr, buf, X86_BUG_CPU_MELTDOWN); 2956 } 2957 2958 ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf) 2959 { 2960 return cpu_show_common(dev, attr, buf, X86_BUG_SPECTRE_V1); 2961 } 2962 2963 ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf) 2964 { 2965 return cpu_show_common(dev, attr, buf, X86_BUG_SPECTRE_V2); 2966 } 2967 2968 ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf) 2969 { 2970 return cpu_show_common(dev, attr, buf, X86_BUG_SPEC_STORE_BYPASS); 2971 } 2972 2973 ssize_t cpu_show_l1tf(struct device *dev, struct device_attribute *attr, char *buf) 2974 { 2975 return cpu_show_common(dev, attr, buf, X86_BUG_L1TF); 2976 } 2977 2978 ssize_t cpu_show_mds(struct device *dev, struct device_attribute *attr, char *buf) 2979 { 2980 return cpu_show_common(dev, attr, buf, X86_BUG_MDS); 2981 } 2982 2983 ssize_t cpu_show_tsx_async_abort(struct device *dev, struct device_attribute *attr, char *buf) 2984 { 2985 return cpu_show_common(dev, attr, buf, X86_BUG_TAA); 2986 } 2987 2988 ssize_t cpu_show_itlb_multihit(struct device *dev, struct device_attribute *attr, char *buf) 2989 { 2990 return cpu_show_common(dev, attr, buf, X86_BUG_ITLB_MULTIHIT); 2991 } 2992 2993 ssize_t cpu_show_srbds(struct device *dev, struct device_attribute *attr, char *buf) 2994 { 2995 return cpu_show_common(dev, attr, buf, X86_BUG_SRBDS); 2996 } 2997 2998 ssize_t cpu_show_mmio_stale_data(struct device *dev, struct device_attribute *attr, char *buf) 2999 { 3000 if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN)) 3001 return cpu_show_common(dev, attr, buf, X86_BUG_MMIO_UNKNOWN); 3002 else 3003 return cpu_show_common(dev, attr, buf, X86_BUG_MMIO_STALE_DATA); 3004 } 3005 3006 ssize_t cpu_show_retbleed(struct device *dev, struct device_attribute *attr, char *buf) 3007 { 3008 return cpu_show_common(dev, attr, buf, X86_BUG_RETBLEED); 3009 } 3010 3011 ssize_t cpu_show_spec_rstack_overflow(struct device *dev, struct device_attribute *attr, char *buf) 3012 { 3013 return cpu_show_common(dev, attr, buf, X86_BUG_SRSO); 3014 } 3015 3016 ssize_t cpu_show_gds(struct device *dev, struct device_attribute *attr, char *buf) 3017 { 3018 return cpu_show_common(dev, attr, buf, X86_BUG_GDS); 3019 } 3020 3021 ssize_t cpu_show_reg_file_data_sampling(struct device *dev, struct device_attribute *attr, char *buf) 3022 { 3023 return cpu_show_common(dev, attr, buf, X86_BUG_RFDS); 3024 } 3025 #endif 3026 3027 void __warn_thunk(void) 3028 { 3029 WARN_ONCE(1, "Unpatched return thunk in use. This should not happen!\n"); 3030 } 3031