1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * PowerPC version 4 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) 5 * 6 * Derived from "arch/i386/mm/fault.c" 7 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 8 * 9 * Modified by Cort Dougan and Paul Mackerras. 10 * 11 * Modified for PPC64 by Dave Engebretsen (engebret@ibm.com) 12 */ 13 14 #include <linux/signal.h> 15 #include <linux/sched.h> 16 #include <linux/sched/task_stack.h> 17 #include <linux/kernel.h> 18 #include <linux/errno.h> 19 #include <linux/string.h> 20 #include <linux/types.h> 21 #include <linux/pagemap.h> 22 #include <linux/ptrace.h> 23 #include <linux/mman.h> 24 #include <linux/mm.h> 25 #include <linux/interrupt.h> 26 #include <linux/highmem.h> 27 #include <linux/extable.h> 28 #include <linux/kprobes.h> 29 #include <linux/kdebug.h> 30 #include <linux/perf_event.h> 31 #include <linux/ratelimit.h> 32 #include <linux/context_tracking.h> 33 #include <linux/hugetlb.h> 34 #include <linux/uaccess.h> 35 #include <linux/kfence.h> 36 #include <linux/pkeys.h> 37 38 #include <asm/firmware.h> 39 #include <asm/interrupt.h> 40 #include <asm/page.h> 41 #include <asm/mmu.h> 42 #include <asm/mmu_context.h> 43 #include <asm/siginfo.h> 44 #include <asm/debug.h> 45 #include <asm/kup.h> 46 #include <asm/inst.h> 47 48 49 /* 50 * do_page_fault error handling helpers 51 */ 52 53 static int 54 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long address, int si_code) 55 { 56 /* 57 * If we are in kernel mode, bail out with a SEGV, this will 58 * be caught by the assembly which will restore the non-volatile 59 * registers before calling bad_page_fault() 60 */ 61 if (!user_mode(regs)) 62 return SIGSEGV; 63 64 _exception(SIGSEGV, regs, si_code, address); 65 66 return 0; 67 } 68 69 static noinline int bad_area_nosemaphore(struct pt_regs *regs, unsigned long address) 70 { 71 return __bad_area_nosemaphore(regs, address, SEGV_MAPERR); 72 } 73 74 static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code) 75 { 76 struct mm_struct *mm = current->mm; 77 78 /* 79 * Something tried to access memory that isn't in our memory map.. 80 * Fix it, but check if it's kernel or user first.. 81 */ 82 mmap_read_unlock(mm); 83 84 return __bad_area_nosemaphore(regs, address, si_code); 85 } 86 87 static noinline int bad_area(struct pt_regs *regs, unsigned long address) 88 { 89 return __bad_area(regs, address, SEGV_MAPERR); 90 } 91 92 static noinline int bad_access_pkey(struct pt_regs *regs, unsigned long address, 93 struct vm_area_struct *vma) 94 { 95 struct mm_struct *mm = current->mm; 96 int pkey; 97 98 /* 99 * We don't try to fetch the pkey from page table because reading 100 * page table without locking doesn't guarantee stable pte value. 101 * Hence the pkey value that we return to userspace can be different 102 * from the pkey that actually caused access error. 103 * 104 * It does *not* guarantee that the VMA we find here 105 * was the one that we faulted on. 106 * 107 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4); 108 * 2. T1 : set AMR to deny access to pkey=4, touches, page 109 * 3. T1 : faults... 110 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5); 111 * 5. T1 : enters fault handler, takes mmap_lock, etc... 112 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really 113 * faulted on a pte with its pkey=4. 114 */ 115 pkey = vma_pkey(vma); 116 117 mmap_read_unlock(mm); 118 119 /* 120 * If we are in kernel mode, bail out with a SEGV, this will 121 * be caught by the assembly which will restore the non-volatile 122 * registers before calling bad_page_fault() 123 */ 124 if (!user_mode(regs)) 125 return SIGSEGV; 126 127 _exception_pkey(regs, address, pkey); 128 129 return 0; 130 } 131 132 static noinline int bad_access(struct pt_regs *regs, unsigned long address) 133 { 134 return __bad_area(regs, address, SEGV_ACCERR); 135 } 136 137 static int do_sigbus(struct pt_regs *regs, unsigned long address, 138 vm_fault_t fault) 139 { 140 if (!user_mode(regs)) 141 return SIGBUS; 142 143 current->thread.trap_nr = BUS_ADRERR; 144 #ifdef CONFIG_MEMORY_FAILURE 145 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { 146 unsigned int lsb = 0; /* shutup gcc */ 147 148 pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", 149 current->comm, current->pid, address); 150 151 if (fault & VM_FAULT_HWPOISON_LARGE) 152 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 153 if (fault & VM_FAULT_HWPOISON) 154 lsb = PAGE_SHIFT; 155 156 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb); 157 return 0; 158 } 159 160 #endif 161 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address); 162 return 0; 163 } 164 165 static int mm_fault_error(struct pt_regs *regs, unsigned long addr, 166 vm_fault_t fault) 167 { 168 /* 169 * Kernel page fault interrupted by SIGKILL. We have no reason to 170 * continue processing. 171 */ 172 if (fatal_signal_pending(current) && !user_mode(regs)) 173 return SIGKILL; 174 175 /* Out of memory */ 176 if (fault & VM_FAULT_OOM) { 177 /* 178 * We ran out of memory, or some other thing happened to us that 179 * made us unable to handle the page fault gracefully. 180 */ 181 if (!user_mode(regs)) 182 return SIGSEGV; 183 pagefault_out_of_memory(); 184 } else { 185 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| 186 VM_FAULT_HWPOISON_LARGE)) 187 return do_sigbus(regs, addr, fault); 188 else if (fault & VM_FAULT_SIGSEGV) 189 return bad_area_nosemaphore(regs, addr); 190 else 191 BUG(); 192 } 193 return 0; 194 } 195 196 /* Is this a bad kernel fault ? */ 197 static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code, 198 unsigned long address, bool is_write) 199 { 200 int is_exec = TRAP(regs) == INTERRUPT_INST_STORAGE; 201 202 if (is_exec) { 203 pr_crit_ratelimited("kernel tried to execute %s page (%lx) - exploit attempt? (uid: %d)\n", 204 address >= TASK_SIZE ? "exec-protected" : "user", 205 address, 206 from_kuid(&init_user_ns, current_uid())); 207 208 // Kernel exec fault is always bad 209 return true; 210 } 211 212 // Kernel fault on kernel address is bad 213 if (address >= TASK_SIZE) 214 return true; 215 216 // Read/write fault blocked by KUAP is bad, it can never succeed. 217 if (bad_kuap_fault(regs, address, is_write)) { 218 pr_crit_ratelimited("Kernel attempted to %s user page (%lx) - exploit attempt? (uid: %d)\n", 219 is_write ? "write" : "read", address, 220 from_kuid(&init_user_ns, current_uid())); 221 222 // Fault on user outside of certain regions (eg. copy_tofrom_user()) is bad 223 if (!search_exception_tables(regs->nip)) 224 return true; 225 226 // Read/write fault in a valid region (the exception table search passed 227 // above), but blocked by KUAP is bad, it can never succeed. 228 return WARN(true, "Bug: %s fault blocked by KUAP!", is_write ? "Write" : "Read"); 229 } 230 231 // What's left? Kernel fault on user and allowed by KUAP in the faulting context. 232 return false; 233 } 234 235 static bool access_pkey_error(bool is_write, bool is_exec, bool is_pkey, 236 struct vm_area_struct *vma) 237 { 238 /* 239 * Make sure to check the VMA so that we do not perform 240 * faults just to hit a pkey fault as soon as we fill in a 241 * page. Only called for current mm, hence foreign == 0 242 */ 243 if (!arch_vma_access_permitted(vma, is_write, is_exec, 0)) 244 return true; 245 246 return false; 247 } 248 249 static bool access_error(bool is_write, bool is_exec, struct vm_area_struct *vma) 250 { 251 /* 252 * Allow execution from readable areas if the MMU does not 253 * provide separate controls over reading and executing. 254 * 255 * Note: That code used to not be enabled for 4xx/BookE. 256 * It is now as I/D cache coherency for these is done at 257 * set_pte_at() time and I see no reason why the test 258 * below wouldn't be valid on those processors. This -may- 259 * break programs compiled with a really old ABI though. 260 */ 261 if (is_exec) { 262 return !(vma->vm_flags & VM_EXEC) && 263 (cpu_has_feature(CPU_FTR_NOEXECUTE) || 264 !(vma->vm_flags & (VM_READ | VM_WRITE))); 265 } 266 267 if (is_write) { 268 if (unlikely(!(vma->vm_flags & VM_WRITE))) 269 return true; 270 return false; 271 } 272 273 /* 274 * Check for a read fault. This could be caused by a read on an 275 * inaccessible page (i.e. PROT_NONE), or a Radix MMU execute-only page. 276 */ 277 if (unlikely(!(vma->vm_flags & VM_READ))) 278 return true; 279 /* 280 * We should ideally do the vma pkey access check here. But in the 281 * fault path, handle_mm_fault() also does the same check. To avoid 282 * these multiple checks, we skip it here and handle access error due 283 * to pkeys later. 284 */ 285 return false; 286 } 287 288 #ifdef CONFIG_PPC_SMLPAR 289 static inline void cmo_account_page_fault(void) 290 { 291 if (firmware_has_feature(FW_FEATURE_CMO)) { 292 u32 page_ins; 293 294 preempt_disable(); 295 page_ins = be32_to_cpu(get_lppaca()->page_ins); 296 page_ins += 1 << PAGE_FACTOR; 297 get_lppaca()->page_ins = cpu_to_be32(page_ins); 298 preempt_enable(); 299 } 300 } 301 #else 302 static inline void cmo_account_page_fault(void) { } 303 #endif /* CONFIG_PPC_SMLPAR */ 304 305 static void sanity_check_fault(bool is_write, bool is_user, 306 unsigned long error_code, unsigned long address) 307 { 308 /* 309 * Userspace trying to access kernel address, we get PROTFAULT for that. 310 */ 311 if (is_user && address >= TASK_SIZE) { 312 if ((long)address == -1) 313 return; 314 315 pr_crit_ratelimited("%s[%d]: User access of kernel address (%lx) - exploit attempt? (uid: %d)\n", 316 current->comm, current->pid, address, 317 from_kuid(&init_user_ns, current_uid())); 318 return; 319 } 320 321 if (!IS_ENABLED(CONFIG_PPC_BOOK3S)) 322 return; 323 324 /* 325 * For hash translation mode, we should never get a 326 * PROTFAULT. Any update to pte to reduce access will result in us 327 * removing the hash page table entry, thus resulting in a DSISR_NOHPTE 328 * fault instead of DSISR_PROTFAULT. 329 * 330 * A pte update to relax the access will not result in a hash page table 331 * entry invalidate and hence can result in DSISR_PROTFAULT. 332 * ptep_set_access_flags() doesn't do a hpte flush. This is why we have 333 * the special !is_write in the below conditional. 334 * 335 * For platforms that doesn't supports coherent icache and do support 336 * per page noexec bit, we do setup things such that we do the 337 * sync between D/I cache via fault. But that is handled via low level 338 * hash fault code (hash_page_do_lazy_icache()) and we should not reach 339 * here in such case. 340 * 341 * For wrong access that can result in PROTFAULT, the above vma->vm_flags 342 * check should handle those and hence we should fall to the bad_area 343 * handling correctly. 344 * 345 * For embedded with per page exec support that doesn't support coherent 346 * icache we do get PROTFAULT and we handle that D/I cache sync in 347 * set_pte_at while taking the noexec/prot fault. Hence this is WARN_ON 348 * is conditional for server MMU. 349 * 350 * For radix, we can get prot fault for autonuma case, because radix 351 * page table will have them marked noaccess for user. 352 */ 353 if (radix_enabled() || is_write) 354 return; 355 356 WARN_ON_ONCE(error_code & DSISR_PROTFAULT); 357 } 358 359 /* 360 * Define the correct "is_write" bit in error_code based 361 * on the processor family 362 */ 363 #if (defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 364 #define page_fault_is_write(__err) ((__err) & ESR_DST) 365 #else 366 #define page_fault_is_write(__err) ((__err) & DSISR_ISSTORE) 367 #endif 368 369 #if defined(CONFIG_4xx) || defined(CONFIG_BOOKE) 370 #define page_fault_is_bad(__err) (0) 371 #elif defined(CONFIG_PPC_8xx) 372 #define page_fault_is_bad(__err) ((__err) & DSISR_NOEXEC_OR_G) 373 #elif defined(CONFIG_PPC64) 374 static int page_fault_is_bad(unsigned long err) 375 { 376 unsigned long flag = DSISR_BAD_FAULT_64S; 377 378 /* 379 * PAPR+ v2.11 § 14.15.3.4.1 (unreleased) 380 * If byte 0, bit 3 of pi-attribute-specifier-type in 381 * ibm,pi-features property is defined, ignore the DSI error 382 * which is caused by the paste instruction on the 383 * suspended NX window. 384 */ 385 if (mmu_has_feature(MMU_FTR_NX_DSI)) 386 flag &= ~DSISR_BAD_COPYPASTE; 387 388 return err & flag; 389 } 390 #else 391 #define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_32S) 392 #endif 393 394 /* 395 * For 600- and 800-family processors, the error_code parameter is DSISR 396 * for a data fault, SRR1 for an instruction fault. 397 * For 400-family processors the error_code parameter is ESR for a data fault, 398 * 0 for an instruction fault. 399 * For 64-bit processors, the error_code parameter is DSISR for a data access 400 * fault, SRR1 & 0x08000000 for an instruction access fault. 401 * 402 * The return value is 0 if the fault was handled, or the signal 403 * number if this is a kernel fault that can't be handled here. 404 */ 405 static int ___do_page_fault(struct pt_regs *regs, unsigned long address, 406 unsigned long error_code) 407 { 408 struct vm_area_struct * vma; 409 struct mm_struct *mm = current->mm; 410 unsigned int flags = FAULT_FLAG_DEFAULT; 411 int is_exec = TRAP(regs) == INTERRUPT_INST_STORAGE; 412 int is_user = user_mode(regs); 413 int is_write = page_fault_is_write(error_code); 414 vm_fault_t fault, major = 0; 415 bool kprobe_fault = kprobe_page_fault(regs, 11); 416 417 if (unlikely(debugger_fault_handler(regs) || kprobe_fault)) 418 return 0; 419 420 if (unlikely(page_fault_is_bad(error_code))) { 421 if (is_user) { 422 _exception(SIGBUS, regs, BUS_OBJERR, address); 423 return 0; 424 } 425 return SIGBUS; 426 } 427 428 /* Additional sanity check(s) */ 429 sanity_check_fault(is_write, is_user, error_code, address); 430 431 /* 432 * The kernel should never take an execute fault nor should it 433 * take a page fault to a kernel address or a page fault to a user 434 * address outside of dedicated places 435 */ 436 if (unlikely(!is_user && bad_kernel_fault(regs, error_code, address, is_write))) { 437 if (kfence_handle_page_fault(address, is_write, regs)) 438 return 0; 439 440 return SIGSEGV; 441 } 442 443 /* 444 * If we're in an interrupt, have no user context or are running 445 * in a region with pagefaults disabled then we must not take the fault 446 */ 447 if (unlikely(faulthandler_disabled() || !mm)) { 448 if (is_user) 449 printk_ratelimited(KERN_ERR "Page fault in user mode" 450 " with faulthandler_disabled()=%d" 451 " mm=%p\n", 452 faulthandler_disabled(), mm); 453 return bad_area_nosemaphore(regs, address); 454 } 455 456 interrupt_cond_local_irq_enable(regs); 457 458 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 459 460 /* 461 * We want to do this outside mmap_lock, because reading code around nip 462 * can result in fault, which will cause a deadlock when called with 463 * mmap_lock held 464 */ 465 if (is_user) 466 flags |= FAULT_FLAG_USER; 467 if (is_write) 468 flags |= FAULT_FLAG_WRITE; 469 if (is_exec) 470 flags |= FAULT_FLAG_INSTRUCTION; 471 472 /* When running in the kernel we expect faults to occur only to 473 * addresses in user space. All other faults represent errors in the 474 * kernel and should generate an OOPS. Unfortunately, in the case of an 475 * erroneous fault occurring in a code path which already holds mmap_lock 476 * we will deadlock attempting to validate the fault against the 477 * address space. Luckily the kernel only validly references user 478 * space from well defined areas of code, which are listed in the 479 * exceptions table. 480 * 481 * As the vast majority of faults will be valid we will only perform 482 * the source reference check when there is a possibility of a deadlock. 483 * Attempt to lock the address space, if we cannot we then validate the 484 * source. If this is invalid we can skip the address space check, 485 * thus avoiding the deadlock. 486 */ 487 if (unlikely(!mmap_read_trylock(mm))) { 488 if (!is_user && !search_exception_tables(regs->nip)) 489 return bad_area_nosemaphore(regs, address); 490 491 retry: 492 mmap_read_lock(mm); 493 } else { 494 /* 495 * The above down_read_trylock() might have succeeded in 496 * which case we'll have missed the might_sleep() from 497 * down_read(): 498 */ 499 might_sleep(); 500 } 501 502 vma = find_vma(mm, address); 503 if (unlikely(!vma)) 504 return bad_area(regs, address); 505 506 if (unlikely(vma->vm_start > address)) { 507 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) 508 return bad_area(regs, address); 509 510 if (unlikely(expand_stack(vma, address))) 511 return bad_area(regs, address); 512 } 513 514 if (unlikely(access_pkey_error(is_write, is_exec, 515 (error_code & DSISR_KEYFAULT), vma))) 516 return bad_access_pkey(regs, address, vma); 517 518 if (unlikely(access_error(is_write, is_exec, vma))) 519 return bad_access(regs, address); 520 521 /* 522 * If for any reason at all we couldn't handle the fault, 523 * make sure we exit gracefully rather than endlessly redo 524 * the fault. 525 */ 526 fault = handle_mm_fault(vma, address, flags, regs); 527 528 major |= fault & VM_FAULT_MAJOR; 529 530 if (fault_signal_pending(fault, regs)) 531 return user_mode(regs) ? 0 : SIGBUS; 532 533 /* The fault is fully completed (including releasing mmap lock) */ 534 if (fault & VM_FAULT_COMPLETED) 535 goto out; 536 537 /* 538 * Handle the retry right now, the mmap_lock has been released in that 539 * case. 540 */ 541 if (unlikely(fault & VM_FAULT_RETRY)) { 542 flags |= FAULT_FLAG_TRIED; 543 goto retry; 544 } 545 546 mmap_read_unlock(current->mm); 547 548 if (unlikely(fault & VM_FAULT_ERROR)) 549 return mm_fault_error(regs, address, fault); 550 551 out: 552 /* 553 * Major/minor page fault accounting. 554 */ 555 if (major) 556 cmo_account_page_fault(); 557 558 return 0; 559 } 560 NOKPROBE_SYMBOL(___do_page_fault); 561 562 static __always_inline void __do_page_fault(struct pt_regs *regs) 563 { 564 long err; 565 566 err = ___do_page_fault(regs, regs->dar, regs->dsisr); 567 if (unlikely(err)) 568 bad_page_fault(regs, err); 569 } 570 571 DEFINE_INTERRUPT_HANDLER(do_page_fault) 572 { 573 __do_page_fault(regs); 574 } 575 576 #ifdef CONFIG_PPC_BOOK3S_64 577 /* Same as do_page_fault but interrupt entry has already run in do_hash_fault */ 578 void hash__do_page_fault(struct pt_regs *regs) 579 { 580 __do_page_fault(regs); 581 } 582 NOKPROBE_SYMBOL(hash__do_page_fault); 583 #endif 584 585 /* 586 * bad_page_fault is called when we have a bad access from the kernel. 587 * It is called from the DSI and ISI handlers in head.S and from some 588 * of the procedures in traps.c. 589 */ 590 static void __bad_page_fault(struct pt_regs *regs, int sig) 591 { 592 int is_write = page_fault_is_write(regs->dsisr); 593 const char *msg; 594 595 /* kernel has accessed a bad area */ 596 597 if (regs->dar < PAGE_SIZE) 598 msg = "Kernel NULL pointer dereference"; 599 else 600 msg = "Unable to handle kernel data access"; 601 602 switch (TRAP(regs)) { 603 case INTERRUPT_DATA_STORAGE: 604 case INTERRUPT_H_DATA_STORAGE: 605 pr_alert("BUG: %s on %s at 0x%08lx\n", msg, 606 is_write ? "write" : "read", regs->dar); 607 break; 608 case INTERRUPT_DATA_SEGMENT: 609 pr_alert("BUG: %s at 0x%08lx\n", msg, regs->dar); 610 break; 611 case INTERRUPT_INST_STORAGE: 612 case INTERRUPT_INST_SEGMENT: 613 pr_alert("BUG: Unable to handle kernel instruction fetch%s", 614 regs->nip < PAGE_SIZE ? " (NULL pointer?)\n" : "\n"); 615 break; 616 case INTERRUPT_ALIGNMENT: 617 pr_alert("BUG: Unable to handle kernel unaligned access at 0x%08lx\n", 618 regs->dar); 619 break; 620 default: 621 pr_alert("BUG: Unable to handle unknown paging fault at 0x%08lx\n", 622 regs->dar); 623 break; 624 } 625 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", 626 regs->nip); 627 628 if (task_stack_end_corrupted(current)) 629 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n"); 630 631 die("Kernel access of bad area", regs, sig); 632 } 633 634 void bad_page_fault(struct pt_regs *regs, int sig) 635 { 636 const struct exception_table_entry *entry; 637 638 /* Are we prepared to handle this fault? */ 639 entry = search_exception_tables(instruction_pointer(regs)); 640 if (entry) 641 instruction_pointer_set(regs, extable_fixup(entry)); 642 else 643 __bad_page_fault(regs, sig); 644 } 645 646 #ifdef CONFIG_PPC_BOOK3S_64 647 DEFINE_INTERRUPT_HANDLER(do_bad_page_fault_segv) 648 { 649 bad_page_fault(regs, SIGSEGV); 650 } 651 652 /* 653 * In radix, segment interrupts indicate the EA is not addressable by the 654 * page table geometry, so they are always sent here. 655 * 656 * In hash, this is called if do_slb_fault returns error. Typically it is 657 * because the EA was outside the region allowed by software. 658 */ 659 DEFINE_INTERRUPT_HANDLER(do_bad_segment_interrupt) 660 { 661 int err = regs->result; 662 663 if (err == -EFAULT) { 664 if (user_mode(regs)) 665 _exception(SIGSEGV, regs, SEGV_BNDERR, regs->dar); 666 else 667 bad_page_fault(regs, SIGSEGV); 668 } else if (err == -EINVAL) { 669 unrecoverable_exception(regs); 670 } else { 671 BUG(); 672 } 673 } 674 #endif 675