1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 1995 Linus Torvalds 4 * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs. 5 * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar 6 */ 7 #include <linux/sched.h> /* test_thread_flag(), ... */ 8 #include <linux/sched/task_stack.h> /* task_stack_*(), ... */ 9 #include <linux/kdebug.h> /* oops_begin/end, ... */ 10 #include <linux/memblock.h> /* max_low_pfn */ 11 #include <linux/bpf_defs.h> /* bpf_arena_handle_page_fault */ 12 #include <linux/kfence.h> /* kfence_handle_page_fault */ 13 #include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */ 14 #include <linux/mmiotrace.h> /* kmmio_handler, ... */ 15 #include <linux/perf_event.h> /* perf_sw_event */ 16 #include <linux/hugetlb.h> /* hstate_index_to_shift */ 17 #include <linux/context_tracking.h> /* exception_enter(), ... */ 18 #include <linux/uaccess.h> /* faulthandler_disabled() */ 19 #include <linux/efi.h> /* efi_crash_gracefully_on_page_fault()*/ 20 #include <linux/mm_types.h> 21 #include <linux/mm.h> /* find_and_lock_vma() */ 22 #include <linux/vmalloc.h> 23 24 #include <asm/cpufeature.h> /* boot_cpu_has, ... */ 25 #include <asm/traps.h> /* dotraplinkage, ... */ 26 #include <asm/fixmap.h> /* VSYSCALL_ADDR */ 27 #include <asm/vsyscall.h> /* emulate_vsyscall */ 28 #include <asm/vm86.h> /* struct vm86 */ 29 #include <asm/mmu_context.h> /* vma_pkey() */ 30 #include <asm/efi.h> /* efi_crash_gracefully_on_page_fault()*/ 31 #include <asm/desc.h> /* store_idt(), ... */ 32 #include <asm/cpu_entry_area.h> /* exception stack */ 33 #include <asm/pgtable_areas.h> /* VMALLOC_START, ... */ 34 #include <asm/kvm_para.h> /* kvm_handle_async_pf */ 35 #include <asm/vdso.h> /* fixup_vdso_exception() */ 36 #include <asm/irq_stack.h> 37 #include <asm/fred.h> 38 #include <asm/sev.h> /* snp_dump_hva_rmpentry() */ 39 40 #define CREATE_TRACE_POINTS 41 #include <trace/events/exceptions.h> 42 43 /* 44 * Returns 0 if mmiotrace is disabled, or if the fault is not 45 * handled by mmiotrace: 46 */ 47 static nokprobe_inline int 48 kmmio_fault(struct pt_regs *regs, unsigned long addr) 49 { 50 if (unlikely(is_kmmio_active())) 51 if (kmmio_handler(regs, addr) == 1) 52 return -1; 53 return 0; 54 } 55 56 /* 57 * Prefetch quirks: 58 * 59 * 32-bit mode: 60 * 61 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. 62 * Check that here and ignore it. This is AMD erratum #91. 63 * 64 * 64-bit mode: 65 * 66 * Sometimes the CPU reports invalid exceptions on prefetch. 67 * Check that here and ignore it. 68 * 69 * Opcode checker based on code by Richard Brunner. 70 */ 71 static inline int 72 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, 73 unsigned char opcode, int *prefetch) 74 { 75 unsigned char instr_hi = opcode & 0xf0; 76 unsigned char instr_lo = opcode & 0x0f; 77 78 switch (instr_hi) { 79 case 0x20: 80 case 0x30: 81 /* 82 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. 83 * In X86_64 long mode, the CPU will signal invalid 84 * opcode if some of these prefixes are present so 85 * X86_64 will never get here anyway 86 */ 87 return ((instr_lo & 7) == 0x6); 88 #ifdef CONFIG_X86_64 89 case 0x40: 90 /* 91 * In 64-bit mode 0x40..0x4F are valid REX prefixes 92 */ 93 return (!user_mode(regs) || user_64bit_mode(regs)); 94 #endif 95 case 0x60: 96 /* 0x64 thru 0x67 are valid prefixes in all modes. */ 97 return (instr_lo & 0xC) == 0x4; 98 case 0xF0: 99 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */ 100 return !instr_lo || (instr_lo>>1) == 1; 101 case 0x00: 102 /* Prefetch instruction is 0x0F0D or 0x0F18 */ 103 if (get_kernel_nofault(opcode, instr)) 104 return 0; 105 106 *prefetch = (instr_lo == 0xF) && 107 (opcode == 0x0D || opcode == 0x18); 108 return 0; 109 default: 110 return 0; 111 } 112 } 113 114 static bool is_amd_k8_pre_npt(void) 115 { 116 struct cpuinfo_x86 *c = &boot_cpu_data; 117 118 return unlikely(IS_ENABLED(CONFIG_CPU_SUP_AMD) && 119 c->x86_vendor == X86_VENDOR_AMD && 120 c->x86 == 0xf && c->x86_model < 0x40); 121 } 122 123 static int 124 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) 125 { 126 unsigned char *max_instr; 127 unsigned char *instr; 128 int prefetch = 0; 129 130 /* Erratum #91 affects AMD K8, pre-NPT CPUs */ 131 if (!is_amd_k8_pre_npt()) 132 return 0; 133 134 /* 135 * If it was a exec (instruction fetch) fault on NX page, then 136 * do not ignore the fault: 137 */ 138 if (error_code & X86_PF_INSTR) 139 return 0; 140 141 instr = (void *)convert_ip_to_linear(current, regs); 142 max_instr = instr + 15; 143 144 /* 145 * This code has historically always bailed out if IP points to a 146 * not-present page (e.g. due to a race). No one has ever 147 * complained about this. 148 */ 149 pagefault_disable(); 150 151 while (instr < max_instr) { 152 unsigned char opcode; 153 154 if (user_mode(regs)) { 155 if (get_user(opcode, (unsigned char __user *) instr)) 156 break; 157 } else { 158 if (get_kernel_nofault(opcode, instr)) 159 break; 160 } 161 162 instr++; 163 164 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch)) 165 break; 166 } 167 168 pagefault_enable(); 169 return prefetch; 170 } 171 172 DEFINE_SPINLOCK(pgd_lock); 173 LIST_HEAD(pgd_list); 174 175 #ifdef CONFIG_X86_32 176 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) 177 { 178 unsigned index = pgd_index(address); 179 pgd_t *pgd_k; 180 p4d_t *p4d, *p4d_k; 181 pud_t *pud, *pud_k; 182 pmd_t *pmd, *pmd_k; 183 184 pgd += index; 185 pgd_k = init_mm.pgd + index; 186 187 if (!pgd_present(*pgd_k)) 188 return NULL; 189 190 /* 191 * set_pgd(pgd, *pgd_k); here would be useless on PAE 192 * and redundant with the set_pmd() on non-PAE. As would 193 * set_p4d/set_pud. 194 */ 195 p4d = p4d_offset(pgd, address); 196 p4d_k = p4d_offset(pgd_k, address); 197 if (!p4d_present(*p4d_k)) 198 return NULL; 199 200 pud = pud_offset(p4d, address); 201 pud_k = pud_offset(p4d_k, address); 202 if (!pud_present(*pud_k)) 203 return NULL; 204 205 pmd = pmd_offset(pud, address); 206 pmd_k = pmd_offset(pud_k, address); 207 208 if (pmd_present(*pmd) != pmd_present(*pmd_k)) 209 set_pmd(pmd, *pmd_k); 210 211 if (!pmd_present(*pmd_k)) 212 return NULL; 213 else 214 BUG_ON(pmd_pfn(*pmd) != pmd_pfn(*pmd_k)); 215 216 return pmd_k; 217 } 218 219 /* 220 * Handle a fault on the vmalloc or module mapping area 221 * 222 * This is needed because there is a race condition between the time 223 * when the vmalloc mapping code updates the PMD to the point in time 224 * where it synchronizes this update with the other page-tables in the 225 * system. 226 * 227 * In this race window another thread/CPU can map an area on the same 228 * PMD, finds it already present and does not synchronize it with the 229 * rest of the system yet. As a result v[mz]alloc might return areas 230 * which are not mapped in every page-table in the system, causing an 231 * unhandled page-fault when they are accessed. 232 */ 233 static noinline int vmalloc_fault(unsigned long address) 234 { 235 unsigned long pgd_paddr; 236 pmd_t *pmd_k; 237 pte_t *pte_k; 238 239 /* Make sure we are in vmalloc area: */ 240 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 241 return -1; 242 243 /* 244 * Synchronize this task's top level page-table 245 * with the 'reference' page table. 246 * 247 * Do _not_ use "current" here. We might be inside 248 * an interrupt in the middle of a task switch.. 249 */ 250 pgd_paddr = read_cr3_pa(); 251 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); 252 if (!pmd_k) 253 return -1; 254 255 if (pmd_leaf(*pmd_k)) 256 return 0; 257 258 pte_k = pte_offset_kernel(pmd_k, address); 259 if (!pte_present(*pte_k)) 260 return -1; 261 262 return 0; 263 } 264 NOKPROBE_SYMBOL(vmalloc_fault); 265 266 void arch_sync_kernel_mappings(unsigned long start, unsigned long end) 267 { 268 unsigned long addr; 269 270 for (addr = start & PMD_MASK; 271 addr >= TASK_SIZE_MAX && addr < VMALLOC_END; 272 addr += PMD_SIZE) { 273 struct page *page; 274 275 spin_lock(&pgd_lock); 276 list_for_each_entry(page, &pgd_list, lru) { 277 spinlock_t *pgt_lock; 278 279 /* the pgt_lock only for Xen */ 280 pgt_lock = &pgd_page_get_mm(page)->page_table_lock; 281 282 spin_lock(pgt_lock); 283 vmalloc_sync_one(page_address(page), addr); 284 spin_unlock(pgt_lock); 285 } 286 spin_unlock(&pgd_lock); 287 } 288 } 289 290 static bool low_pfn(unsigned long pfn) 291 { 292 return pfn < max_low_pfn; 293 } 294 295 static void dump_pagetable(unsigned long address) 296 { 297 pgd_t *base = __va(read_cr3_pa()); 298 pgd_t *pgd = &base[pgd_index(address)]; 299 p4d_t *p4d; 300 pud_t *pud; 301 pmd_t *pmd; 302 pte_t *pte; 303 304 #ifdef CONFIG_X86_PAE 305 pr_info("*pdpt = %016Lx ", pgd_val(*pgd)); 306 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd)) 307 goto out; 308 #define pr_pde pr_cont 309 #else 310 #define pr_pde pr_info 311 #endif 312 p4d = p4d_offset(pgd, address); 313 pud = pud_offset(p4d, address); 314 pmd = pmd_offset(pud, address); 315 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd)); 316 #undef pr_pde 317 318 /* 319 * We must not directly access the pte in the highpte 320 * case if the page table is located in highmem. 321 * And let's rather not kmap-atomic the pte, just in case 322 * it's allocated already: 323 */ 324 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_leaf(*pmd)) 325 goto out; 326 327 pte = pte_offset_kernel(pmd, address); 328 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte)); 329 out: 330 pr_cont("\n"); 331 } 332 333 #else /* CONFIG_X86_64: */ 334 335 #ifdef CONFIG_CPU_SUP_AMD 336 static const char errata93_warning[] = 337 KERN_ERR 338 "******* Your BIOS seems to not contain a fix for K8 errata #93\n" 339 "******* Working around it, but it may cause SEGVs or burn power.\n" 340 "******* Please consider a BIOS update.\n" 341 "******* Disabling USB legacy in the BIOS may also help.\n"; 342 #endif 343 344 static int bad_address(void *p) 345 { 346 unsigned long dummy; 347 348 return get_kernel_nofault(dummy, (unsigned long *)p); 349 } 350 351 static void dump_pagetable(unsigned long address) 352 { 353 pgd_t *base = __va(read_cr3_pa()); 354 pgd_t *pgd = base + pgd_index(address); 355 p4d_t *p4d; 356 pud_t *pud; 357 pmd_t *pmd; 358 pte_t *pte; 359 360 if (bad_address(pgd)) 361 goto bad; 362 363 pr_info("PGD %lx ", pgd_val(*pgd)); 364 365 if (!pgd_present(*pgd)) 366 goto out; 367 368 p4d = p4d_offset(pgd, address); 369 if (bad_address(p4d)) 370 goto bad; 371 372 pr_cont("P4D %lx ", p4d_val(*p4d)); 373 if (!p4d_present(*p4d) || p4d_leaf(*p4d)) 374 goto out; 375 376 pud = pud_offset(p4d, address); 377 if (bad_address(pud)) 378 goto bad; 379 380 pr_cont("PUD %lx ", pud_val(*pud)); 381 if (!pud_present(*pud) || pud_leaf(*pud)) 382 goto out; 383 384 pmd = pmd_offset(pud, address); 385 if (bad_address(pmd)) 386 goto bad; 387 388 pr_cont("PMD %lx ", pmd_val(*pmd)); 389 if (!pmd_present(*pmd) || pmd_leaf(*pmd)) 390 goto out; 391 392 pte = pte_offset_kernel(pmd, address); 393 if (bad_address(pte)) 394 goto bad; 395 396 pr_cont("PTE %lx", pte_val(*pte)); 397 out: 398 pr_cont("\n"); 399 return; 400 bad: 401 pr_info("BAD\n"); 402 } 403 404 #endif /* CONFIG_X86_64 */ 405 406 /* 407 * Workaround for K8 erratum #93 & buggy BIOS. 408 * 409 * BIOS SMM functions are required to use a specific workaround 410 * to avoid corruption of the 64bit RIP register on C stepping K8. 411 * 412 * A lot of BIOS that didn't get tested properly miss this. 413 * 414 * The OS sees this as a page fault with the upper 32bits of RIP cleared. 415 * Try to work around it here. 416 * 417 * Note we only handle faults in kernel here. 418 * Does nothing on 32-bit. 419 */ 420 static int is_errata93(struct pt_regs *regs, unsigned long address) 421 { 422 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD) 423 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD 424 || boot_cpu_data.x86 != 0xf) 425 return 0; 426 427 if (user_mode(regs)) 428 return 0; 429 430 if (address != regs->ip) 431 return 0; 432 433 if ((address >> 32) != 0) 434 return 0; 435 436 address |= 0xffffffffUL << 32; 437 if ((address >= (u64)_stext && address <= (u64)_etext) || 438 (address >= MODULES_VADDR && address <= MODULES_END)) { 439 printk_once(errata93_warning); 440 regs->ip = address; 441 return 1; 442 } 443 #endif 444 return 0; 445 } 446 447 /* 448 * Work around K8 erratum #100 K8 in compat mode occasionally jumps 449 * to illegal addresses >4GB. 450 * 451 * We catch this in the page fault handler because these addresses 452 * are not reachable. Just detect this case and return. Any code 453 * segment in LDT is compatibility mode. 454 */ 455 static int is_errata100(struct pt_regs *regs, unsigned long address) 456 { 457 #ifdef CONFIG_X86_64 458 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32)) 459 return 1; 460 #endif 461 return 0; 462 } 463 464 /* Pentium F0 0F C7 C8 bug workaround: */ 465 static int is_f00f_bug(struct pt_regs *regs, unsigned long error_code, 466 unsigned long address) 467 { 468 #ifdef CONFIG_X86_F00F_BUG 469 if (boot_cpu_has_bug(X86_BUG_F00F) && !(error_code & X86_PF_USER) && 470 idt_is_f00f_address(address)) { 471 handle_invalid_op(regs); 472 return 1; 473 } 474 #endif 475 return 0; 476 } 477 478 static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index) 479 { 480 u32 offset = (index >> 3) * sizeof(struct desc_struct); 481 unsigned long addr; 482 struct ldttss_desc desc; 483 484 if (index == 0) { 485 pr_alert("%s: NULL\n", name); 486 return; 487 } 488 489 if (offset + sizeof(struct ldttss_desc) >= gdt->size) { 490 pr_alert("%s: 0x%hx -- out of bounds\n", name, index); 491 return; 492 } 493 494 if (copy_from_kernel_nofault(&desc, (void *)(gdt->address + offset), 495 sizeof(struct ldttss_desc))) { 496 pr_alert("%s: 0x%hx -- GDT entry is not readable\n", 497 name, index); 498 return; 499 } 500 501 addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24); 502 #ifdef CONFIG_X86_64 503 addr |= ((u64)desc.base3 << 32); 504 #endif 505 pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n", 506 name, index, addr, (desc.limit0 | (desc.limit1 << 16))); 507 } 508 509 static void 510 show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address) 511 { 512 if (!oops_may_print()) 513 return; 514 515 if (error_code & X86_PF_INSTR) { 516 unsigned int level; 517 bool nx, rw; 518 pgd_t *pgd; 519 pte_t *pte; 520 521 pgd = __va(read_cr3_pa()); 522 pgd += pgd_index(address); 523 524 pte = lookup_address_in_pgd_attr(pgd, address, &level, &nx, &rw); 525 526 if (pte && pte_present(*pte) && (!pte_exec(*pte) || nx)) 527 pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n", 528 from_kuid(&init_user_ns, current_uid())); 529 if (pte && pte_present(*pte) && pte_exec(*pte) && !nx && 530 (pgd_flags(*pgd) & _PAGE_USER) && 531 (__read_cr4() & X86_CR4_SMEP)) 532 pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n", 533 from_kuid(&init_user_ns, current_uid())); 534 } 535 536 if (address < PAGE_SIZE && !user_mode(regs)) 537 pr_alert("BUG: kernel NULL pointer dereference, address: %px\n", 538 (void *)address); 539 else 540 pr_alert("BUG: unable to handle page fault for address: %px\n", 541 (void *)address); 542 543 pr_alert("#PF: %s %s in %s mode\n", 544 (error_code & X86_PF_USER) ? "user" : "supervisor", 545 (error_code & X86_PF_INSTR) ? "instruction fetch" : 546 (error_code & X86_PF_WRITE) ? "write access" : 547 "read access", 548 user_mode(regs) ? "user" : "kernel"); 549 pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code, 550 !(error_code & X86_PF_PROT) ? "not-present page" : 551 (error_code & X86_PF_RSVD) ? "reserved bit violation" : 552 (error_code & X86_PF_PK) ? "protection keys violation" : 553 (error_code & X86_PF_RMP) ? "RMP violation" : 554 "permissions violation"); 555 556 if (!(error_code & X86_PF_USER) && user_mode(regs)) { 557 struct desc_ptr idt, gdt; 558 u16 ldtr, tr; 559 560 /* 561 * This can happen for quite a few reasons. The more obvious 562 * ones are faults accessing the GDT, or LDT. Perhaps 563 * surprisingly, if the CPU tries to deliver a benign or 564 * contributory exception from user code and gets a page fault 565 * during delivery, the page fault can be delivered as though 566 * it originated directly from user code. This could happen 567 * due to wrong permissions on the IDT, GDT, LDT, TSS, or 568 * kernel or IST stack. 569 */ 570 store_idt(&idt); 571 572 /* Usable even on Xen PV -- it's just slow. */ 573 native_store_gdt(&gdt); 574 575 pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n", 576 idt.address, idt.size, gdt.address, gdt.size); 577 578 store_ldt(ldtr); 579 show_ldttss(&gdt, "LDTR", ldtr); 580 581 store_tr(tr); 582 show_ldttss(&gdt, "TR", tr); 583 } 584 585 dump_pagetable(address); 586 587 if (error_code & X86_PF_RMP) 588 snp_dump_hva_rmpentry(address); 589 } 590 591 static noinline void 592 pgtable_bad(struct pt_regs *regs, unsigned long error_code, 593 unsigned long address) 594 { 595 struct task_struct *tsk; 596 unsigned long flags; 597 int sig; 598 599 flags = oops_begin(); 600 tsk = current; 601 sig = SIGKILL; 602 603 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", 604 tsk->comm, address); 605 dump_pagetable(address); 606 607 if (__die("Bad pagetable", regs, error_code)) 608 sig = 0; 609 610 oops_end(flags, regs, sig); 611 } 612 613 static void sanitize_error_code(unsigned long address, 614 unsigned long *error_code) 615 { 616 /* 617 * To avoid leaking information about the kernel page 618 * table layout, pretend that user-mode accesses to 619 * kernel addresses are always protection faults. 620 * 621 * NB: This means that failed vsyscalls with vsyscall=none 622 * will have the PROT bit. This doesn't leak any 623 * information and does not appear to cause any problems. 624 */ 625 if (address >= TASK_SIZE_MAX) 626 *error_code |= X86_PF_PROT; 627 } 628 629 static void set_signal_archinfo(unsigned long address, 630 unsigned long error_code) 631 { 632 struct task_struct *tsk = current; 633 634 tsk->thread.trap_nr = X86_TRAP_PF; 635 tsk->thread.error_code = error_code | X86_PF_USER; 636 tsk->thread.cr2 = address; 637 } 638 639 static noinline void 640 page_fault_oops(struct pt_regs *regs, unsigned long error_code, 641 unsigned long address) 642 { 643 #ifdef CONFIG_VMAP_STACK 644 struct stack_info info; 645 #endif 646 unsigned long flags; 647 int sig; 648 649 if (user_mode(regs)) { 650 /* 651 * Implicit kernel access from user mode? Skip the stack 652 * overflow and EFI special cases. 653 */ 654 goto oops; 655 } 656 657 #ifdef CONFIG_VMAP_STACK 658 /* 659 * Stack overflow? During boot, we can fault near the initial 660 * stack in the direct map, but that's not an overflow -- check 661 * that we're in vmalloc space to avoid this. 662 */ 663 if (is_vmalloc_addr((void *)address) && 664 get_stack_guard_info((void *)address, &info)) { 665 /* 666 * We're likely to be running with very little stack space 667 * left. It's plausible that we'd hit this condition but 668 * double-fault even before we get this far, in which case 669 * we're fine: the double-fault handler will deal with it. 670 * 671 * We don't want to make it all the way into the oops code 672 * and then double-fault, though, because we're likely to 673 * break the console driver and lose most of the stack dump. 674 */ 675 call_on_stack(__this_cpu_ist_top_va(DF) - sizeof(void*), 676 handle_stack_overflow, 677 ASM_CALL_ARG3, 678 , [arg1] "r" (regs), [arg2] "r" (address), [arg3] "r" (&info)); 679 680 BUG(); 681 } 682 #endif 683 684 /* 685 * Buggy firmware could access regions which might page fault. If 686 * this happens, EFI has a special OOPS path that will try to 687 * avoid hanging the system. 688 */ 689 if (IS_ENABLED(CONFIG_EFI)) 690 efi_crash_gracefully_on_page_fault(address, regs); 691 692 /* Only not-present faults should be handled by KFENCE or BPF arena. */ 693 if (!(error_code & X86_PF_PROT)) { 694 if (kfence_handle_page_fault(address, error_code & X86_PF_WRITE, regs)) 695 return; 696 if (bpf_arena_handle_page_fault(address, error_code & X86_PF_WRITE, regs->ip)) 697 return; 698 } 699 700 oops: 701 /* 702 * Oops. The kernel tried to access some bad page. We'll have to 703 * terminate things with extreme prejudice: 704 */ 705 flags = oops_begin(); 706 707 show_fault_oops(regs, error_code, address); 708 709 if (task_stack_end_corrupted(current)) 710 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); 711 712 sig = SIGKILL; 713 if (__die("Oops", regs, error_code)) 714 sig = 0; 715 716 /* Executive summary in case the body of the oops scrolled away */ 717 printk(KERN_DEFAULT "CR2: %016lx\n", address); 718 719 oops_end(flags, regs, sig); 720 } 721 722 static noinline void 723 kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code, 724 unsigned long address, int signal, int si_code, 725 u32 pkey) 726 { 727 WARN_ON_ONCE(user_mode(regs)); 728 729 /* Are we prepared to handle this kernel fault? */ 730 if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) 731 return; 732 733 /* 734 * AMD erratum #91 manifests as a spurious page fault on a PREFETCH 735 * instruction. 736 */ 737 if (is_prefetch(regs, error_code, address)) 738 return; 739 740 page_fault_oops(regs, error_code, address); 741 } 742 743 /* 744 * Print out info about fatal segfaults, if the show_unhandled_signals 745 * sysctl is set: 746 */ 747 static inline void 748 show_signal_msg(struct pt_regs *regs, unsigned long error_code, 749 unsigned long address, struct task_struct *tsk) 750 { 751 const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG; 752 /* This is a racy snapshot, but it's better than nothing. */ 753 int cpu = raw_smp_processor_id(); 754 755 if (!unhandled_signal(tsk, SIGSEGV)) 756 return; 757 758 if (!printk_ratelimit()) 759 return; 760 761 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx", 762 loglvl, tsk->comm, task_pid_nr(tsk), address, 763 (void *)regs->ip, (void *)regs->sp, error_code); 764 765 print_vma_addr(KERN_CONT " in ", regs->ip); 766 767 /* 768 * Dump the likely CPU where the fatal segfault happened. 769 * This can help identify faulty hardware. 770 */ 771 printk(KERN_CONT " likely on CPU %d (core %d, socket %d)", cpu, 772 topology_core_id(cpu), topology_physical_package_id(cpu)); 773 774 775 printk(KERN_CONT "\n"); 776 777 show_opcodes(regs, loglvl); 778 } 779 780 static void 781 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 782 unsigned long address, u32 pkey, int si_code) 783 { 784 struct task_struct *tsk = current; 785 786 if (!user_mode(regs)) { 787 kernelmode_fixup_or_oops(regs, error_code, address, 788 SIGSEGV, si_code, pkey); 789 return; 790 } 791 792 if (!(error_code & X86_PF_USER)) { 793 /* Implicit user access to kernel memory -- just oops */ 794 page_fault_oops(regs, error_code, address); 795 return; 796 } 797 798 /* 799 * User mode accesses just cause a SIGSEGV. 800 * It's possible to have interrupts off here: 801 */ 802 local_irq_enable(); 803 804 /* 805 * Valid to do another page fault here because this one came 806 * from user space: 807 */ 808 if (is_prefetch(regs, error_code, address)) 809 return; 810 811 if (is_errata100(regs, address)) 812 return; 813 814 sanitize_error_code(address, &error_code); 815 816 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address)) 817 return; 818 819 if (likely(show_unhandled_signals)) 820 show_signal_msg(regs, error_code, address, tsk); 821 822 set_signal_archinfo(address, error_code); 823 824 if (si_code == SEGV_PKUERR) 825 force_sig_pkuerr((void __user *)address, pkey); 826 else 827 force_sig_fault(SIGSEGV, si_code, (void __user *)address); 828 } 829 830 static noinline void 831 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 832 unsigned long address) 833 { 834 __bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR); 835 } 836 837 static void 838 __bad_area(struct pt_regs *regs, unsigned long error_code, 839 unsigned long address, struct mm_struct *mm, 840 struct vm_area_struct *vma, u32 pkey, int si_code) 841 { 842 /* 843 * Something tried to access memory that isn't in our memory map.. 844 * Fix it, but check if it's kernel or user first.. 845 */ 846 if (mm) 847 mmap_read_unlock(mm); 848 else 849 vma_end_read(vma); 850 851 __bad_area_nosemaphore(regs, error_code, address, pkey, si_code); 852 } 853 854 static inline bool bad_area_access_from_pkeys(unsigned long error_code, 855 struct vm_area_struct *vma) 856 { 857 /* This code is always called on the current mm */ 858 bool foreign = false; 859 860 if (!cpu_feature_enabled(X86_FEATURE_OSPKE)) 861 return false; 862 if (error_code & X86_PF_PK) 863 return true; 864 /* this checks permission keys on the VMA: */ 865 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE), 866 (error_code & X86_PF_INSTR), foreign)) 867 return true; 868 return false; 869 } 870 871 static noinline void 872 bad_area_access_error(struct pt_regs *regs, unsigned long error_code, 873 unsigned long address, struct mm_struct *mm, 874 struct vm_area_struct *vma) 875 { 876 /* 877 * This OSPKE check is not strictly necessary at runtime. 878 * But, doing it this way allows compiler optimizations 879 * if pkeys are compiled out. 880 */ 881 if (bad_area_access_from_pkeys(error_code, vma)) { 882 /* 883 * A protection key fault means that the PKRU value did not allow 884 * access to some PTE. Userspace can figure out what PKRU was 885 * from the XSAVE state. This function captures the pkey from 886 * the vma and passes it to userspace so userspace can discover 887 * which protection key was set on the PTE. 888 * 889 * If we get here, we know that the hardware signaled a X86_PF_PK 890 * fault and that there was a VMA once we got in the fault 891 * handler. It does *not* guarantee that the VMA we find here 892 * was the one that we faulted on. 893 * 894 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4); 895 * 2. T1 : set PKRU to deny access to pkey=4, touches page 896 * 3. T1 : faults... 897 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5); 898 * 5. T1 : enters fault handler, takes mmap_lock, etc... 899 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really 900 * faulted on a pte with its pkey=4. 901 */ 902 u32 pkey = vma_pkey(vma); 903 904 __bad_area(regs, error_code, address, mm, vma, pkey, SEGV_PKUERR); 905 } else { 906 __bad_area(regs, error_code, address, mm, vma, 0, SEGV_ACCERR); 907 } 908 } 909 910 static void 911 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, 912 vm_fault_t fault) 913 { 914 /* Kernel mode? Handle exceptions or die: */ 915 if (!user_mode(regs)) { 916 kernelmode_fixup_or_oops(regs, error_code, address, 917 SIGBUS, BUS_ADRERR, ARCH_DEFAULT_PKEY); 918 return; 919 } 920 921 /* User-space => ok to do another page fault: */ 922 if (is_prefetch(regs, error_code, address)) 923 return; 924 925 sanitize_error_code(address, &error_code); 926 927 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address)) 928 return; 929 930 set_signal_archinfo(address, error_code); 931 932 #ifdef CONFIG_MEMORY_FAILURE 933 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { 934 struct task_struct *tsk = current; 935 unsigned lsb = 0; 936 937 pr_err( 938 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", 939 tsk->comm, tsk->pid, address); 940 if (fault & VM_FAULT_HWPOISON_LARGE) 941 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 942 if (fault & VM_FAULT_HWPOISON) 943 lsb = PAGE_SHIFT; 944 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb); 945 return; 946 } 947 #endif 948 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address); 949 } 950 951 static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte) 952 { 953 if ((error_code & X86_PF_WRITE) && !pte_write(*pte)) 954 return 0; 955 956 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte)) 957 return 0; 958 959 return 1; 960 } 961 962 /* 963 * Handle a spurious fault caused by a stale TLB entry. 964 * 965 * This allows us to lazily refresh the TLB when increasing the 966 * permissions of a kernel page (RO -> RW or NX -> X). Doing it 967 * eagerly is very expensive since that implies doing a full 968 * cross-processor TLB flush, even if no stale TLB entries exist 969 * on other processors. 970 * 971 * Spurious faults may only occur if the TLB contains an entry with 972 * fewer permission than the page table entry. Non-present (P = 0) 973 * and reserved bit (R = 1) faults are never spurious. 974 * 975 * There are no security implications to leaving a stale TLB when 976 * increasing the permissions on a page. 977 * 978 * Returns non-zero if a spurious fault was handled, zero otherwise. 979 * 980 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3 981 * (Optional Invalidation). 982 */ 983 static noinline int 984 spurious_kernel_fault(unsigned long error_code, unsigned long address) 985 { 986 pgd_t *pgd; 987 p4d_t *p4d; 988 pud_t *pud; 989 pmd_t *pmd; 990 pte_t *pte; 991 int ret; 992 993 /* 994 * Only writes to RO or instruction fetches from NX may cause 995 * spurious faults. 996 * 997 * These could be from user or supervisor accesses but the TLB 998 * is only lazily flushed after a kernel mapping protection 999 * change, so user accesses are not expected to cause spurious 1000 * faults. 1001 */ 1002 if (error_code != (X86_PF_WRITE | X86_PF_PROT) && 1003 error_code != (X86_PF_INSTR | X86_PF_PROT)) 1004 return 0; 1005 1006 pgd = init_mm.pgd + pgd_index(address); 1007 if (!pgd_present(*pgd)) 1008 return 0; 1009 1010 p4d = p4d_offset(pgd, address); 1011 if (!p4d_present(*p4d)) 1012 return 0; 1013 1014 if (p4d_leaf(*p4d)) 1015 return spurious_kernel_fault_check(error_code, (pte_t *) p4d); 1016 1017 pud = pud_offset(p4d, address); 1018 if (!pud_present(*pud)) 1019 return 0; 1020 1021 if (pud_leaf(*pud)) 1022 return spurious_kernel_fault_check(error_code, (pte_t *) pud); 1023 1024 pmd = pmd_offset(pud, address); 1025 if (!pmd_present(*pmd)) 1026 return 0; 1027 1028 if (pmd_leaf(*pmd)) 1029 return spurious_kernel_fault_check(error_code, (pte_t *) pmd); 1030 1031 pte = pte_offset_kernel(pmd, address); 1032 if (!pte_present(*pte)) 1033 return 0; 1034 1035 ret = spurious_kernel_fault_check(error_code, pte); 1036 if (!ret) 1037 return 0; 1038 1039 /* 1040 * Make sure we have permissions in PMD. 1041 * If not, then there's a bug in the page tables: 1042 */ 1043 ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd); 1044 WARN_ONCE(!ret, "PMD has incorrect permission bits\n"); 1045 1046 return ret; 1047 } 1048 NOKPROBE_SYMBOL(spurious_kernel_fault); 1049 1050 int show_unhandled_signals = 1; 1051 1052 static inline int 1053 access_error(unsigned long error_code, struct vm_area_struct *vma) 1054 { 1055 /* This is only called for the current mm, so: */ 1056 bool foreign = false; 1057 1058 /* 1059 * Read or write was blocked by protection keys. This is 1060 * always an unconditional error and can never result in 1061 * a follow-up action to resolve the fault, like a COW. 1062 */ 1063 if (error_code & X86_PF_PK) 1064 return 1; 1065 1066 /* 1067 * SGX hardware blocked the access. This usually happens 1068 * when the enclave memory contents have been destroyed, like 1069 * after a suspend/resume cycle. In any case, the kernel can't 1070 * fix the cause of the fault. Handle the fault as an access 1071 * error even in cases where no actual access violation 1072 * occurred. This allows userspace to rebuild the enclave in 1073 * response to the signal. 1074 */ 1075 if (unlikely(error_code & X86_PF_SGX)) 1076 return 1; 1077 1078 /* 1079 * Make sure to check the VMA so that we do not perform 1080 * faults just to hit a X86_PF_PK as soon as we fill in a 1081 * page. 1082 */ 1083 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE), 1084 (error_code & X86_PF_INSTR), foreign)) 1085 return 1; 1086 1087 /* 1088 * Shadow stack accesses (PF_SHSTK=1) are only permitted to 1089 * shadow stack VMAs. All other accesses result in an error. 1090 */ 1091 if (error_code & X86_PF_SHSTK) { 1092 if (unlikely(!(vma->vm_flags & VM_SHADOW_STACK))) 1093 return 1; 1094 if (unlikely(!(vma->vm_flags & VM_WRITE))) 1095 return 1; 1096 return 0; 1097 } 1098 1099 if (error_code & X86_PF_WRITE) { 1100 /* write, present and write, not present: */ 1101 if (unlikely(vma->vm_flags & VM_SHADOW_STACK)) 1102 return 1; 1103 if (unlikely(!(vma->vm_flags & VM_WRITE))) 1104 return 1; 1105 return 0; 1106 } 1107 1108 /* read, present: */ 1109 if (unlikely(error_code & X86_PF_PROT)) 1110 return 1; 1111 1112 /* read, not present: */ 1113 if (unlikely(!vma_is_accessible(vma))) 1114 return 1; 1115 1116 return 0; 1117 } 1118 1119 bool fault_in_kernel_space(unsigned long address) 1120 { 1121 /* 1122 * On 64-bit systems, the vsyscall page is at an address above 1123 * TASK_SIZE_MAX, but is not considered part of the kernel 1124 * address space. 1125 */ 1126 if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address)) 1127 return false; 1128 1129 return address >= TASK_SIZE_MAX; 1130 } 1131 1132 /* 1133 * Called for all faults where 'address' is part of the kernel address 1134 * space. Might get called for faults that originate from *code* that 1135 * ran in userspace or the kernel. 1136 */ 1137 static void 1138 do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code, 1139 unsigned long address) 1140 { 1141 /* 1142 * Protection keys exceptions only happen on user pages. We 1143 * have no user pages in the kernel portion of the address 1144 * space, so do not expect them here. 1145 */ 1146 WARN_ON_ONCE(hw_error_code & X86_PF_PK); 1147 1148 #ifdef CONFIG_X86_32 1149 /* 1150 * We can fault-in kernel-space virtual memory on-demand. The 1151 * 'reference' page table is init_mm.pgd. 1152 * 1153 * NOTE! We MUST NOT take any locks for this case. We may 1154 * be in an interrupt or a critical region, and should 1155 * only copy the information from the master page table, 1156 * nothing more. 1157 * 1158 * Before doing this on-demand faulting, ensure that the 1159 * fault is not any of the following: 1160 * 1. A fault on a PTE with a reserved bit set. 1161 * 2. A fault caused by a user-mode access. (Do not demand- 1162 * fault kernel memory due to user-mode accesses). 1163 * 3. A fault caused by a page-level protection violation. 1164 * (A demand fault would be on a non-present page which 1165 * would have X86_PF_PROT==0). 1166 * 1167 * This is only needed to close a race condition on x86-32 in 1168 * the vmalloc mapping/unmapping code. See the comment above 1169 * vmalloc_fault() for details. On x86-64 the race does not 1170 * exist as the vmalloc mappings don't need to be synchronized 1171 * there. 1172 */ 1173 if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) { 1174 if (vmalloc_fault(address) >= 0) 1175 return; 1176 } 1177 #endif 1178 1179 if (is_f00f_bug(regs, hw_error_code, address)) 1180 return; 1181 1182 /* Was the fault spurious, caused by lazy TLB invalidation? */ 1183 if (spurious_kernel_fault(hw_error_code, address)) 1184 return; 1185 1186 /* kprobes don't want to hook the spurious faults: */ 1187 if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF))) 1188 return; 1189 1190 /* 1191 * Note, despite being a "bad area", there are quite a few 1192 * acceptable reasons to get here, such as erratum fixups 1193 * and handling kernel code that can fault, like get_user(). 1194 * 1195 * Don't take the mm semaphore here. If we fixup a prefetch 1196 * fault we could otherwise deadlock: 1197 */ 1198 bad_area_nosemaphore(regs, hw_error_code, address); 1199 } 1200 NOKPROBE_SYMBOL(do_kern_addr_fault); 1201 1202 /* 1203 * Handle faults in the user portion of the address space. Nothing in here 1204 * should check X86_PF_USER without a specific justification: for almost 1205 * all purposes, we should treat a normal kernel access to user memory 1206 * (e.g. get_user(), put_user(), etc.) the same as the WRUSS instruction. 1207 * The one exception is AC flag handling, which is, per the x86 1208 * architecture, special for WRUSS. 1209 */ 1210 static inline 1211 void do_user_addr_fault(struct pt_regs *regs, 1212 unsigned long error_code, 1213 unsigned long address) 1214 { 1215 struct vm_area_struct *vma; 1216 struct task_struct *tsk; 1217 struct mm_struct *mm; 1218 vm_fault_t fault; 1219 unsigned int flags = FAULT_FLAG_DEFAULT; 1220 1221 tsk = current; 1222 mm = tsk->mm; 1223 1224 if (unlikely((error_code & (X86_PF_USER | X86_PF_INSTR)) == X86_PF_INSTR)) { 1225 /* 1226 * Whoops, this is kernel mode code trying to execute from 1227 * user memory. Unless this is AMD erratum #93, which 1228 * corrupts RIP such that it looks like a user address, 1229 * this is unrecoverable. Don't even try to look up the 1230 * VMA or look for extable entries. 1231 */ 1232 if (is_errata93(regs, address)) 1233 return; 1234 1235 page_fault_oops(regs, error_code, address); 1236 return; 1237 } 1238 1239 /* kprobes don't want to hook the spurious faults: */ 1240 if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF))) 1241 return; 1242 1243 /* 1244 * Reserved bits are never expected to be set on 1245 * entries in the user portion of the page tables. 1246 */ 1247 if (unlikely(error_code & X86_PF_RSVD)) 1248 pgtable_bad(regs, error_code, address); 1249 1250 /* 1251 * If SMAP is on, check for invalid kernel (supervisor) access to user 1252 * pages in the user address space. The odd case here is WRUSS, 1253 * which, according to the preliminary documentation, does not respect 1254 * SMAP and will have the USER bit set so, in all cases, SMAP 1255 * enforcement appears to be consistent with the USER bit. 1256 */ 1257 if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) && 1258 !(error_code & X86_PF_USER) && 1259 !(regs->flags & X86_EFLAGS_AC))) { 1260 /* 1261 * No extable entry here. This was a kernel access to an 1262 * invalid pointer. get_kernel_nofault() will not get here. 1263 */ 1264 page_fault_oops(regs, error_code, address); 1265 return; 1266 } 1267 1268 /* 1269 * If we're in an interrupt, have no user context or are running 1270 * in a region with pagefaults disabled then we must not take the fault 1271 */ 1272 if (unlikely(faulthandler_disabled() || !mm)) { 1273 bad_area_nosemaphore(regs, error_code, address); 1274 return; 1275 } 1276 1277 /* Legacy check - remove this after verifying that it doesn't trigger */ 1278 if (WARN_ON_ONCE(!(regs->flags & X86_EFLAGS_IF))) { 1279 bad_area_nosemaphore(regs, error_code, address); 1280 return; 1281 } 1282 1283 local_irq_enable(); 1284 1285 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 1286 1287 /* 1288 * Read-only permissions can not be expressed in shadow stack PTEs. 1289 * Treat all shadow stack accesses as WRITE faults. This ensures 1290 * that the MM will prepare everything (e.g., break COW) such that 1291 * maybe_mkwrite() can create a proper shadow stack PTE. 1292 */ 1293 if (error_code & X86_PF_SHSTK) 1294 flags |= FAULT_FLAG_WRITE; 1295 if (error_code & X86_PF_WRITE) 1296 flags |= FAULT_FLAG_WRITE; 1297 if (error_code & X86_PF_INSTR) 1298 flags |= FAULT_FLAG_INSTRUCTION; 1299 1300 /* 1301 * We set FAULT_FLAG_USER based on the register state, not 1302 * based on X86_PF_USER. User space accesses that cause 1303 * system page faults are still user accesses. 1304 */ 1305 if (user_mode(regs)) 1306 flags |= FAULT_FLAG_USER; 1307 1308 #ifdef CONFIG_X86_64 1309 /* 1310 * Faults in the vsyscall page might need emulation. The 1311 * vsyscall page is at a high address (>PAGE_OFFSET), but is 1312 * considered to be part of the user address space. 1313 * 1314 * The vsyscall page does not have a "real" VMA, so do this 1315 * emulation before we go searching for VMAs. 1316 * 1317 * PKRU never rejects instruction fetches, so we don't need 1318 * to consider the PF_PK bit. 1319 */ 1320 if (is_vsyscall_vaddr(address)) { 1321 if (emulate_vsyscall_pf(error_code, regs, address)) 1322 return; 1323 } 1324 #endif 1325 1326 if (!(flags & FAULT_FLAG_USER)) 1327 goto lock_mmap; 1328 1329 vma = lock_vma_under_rcu(mm, address); 1330 if (!vma) 1331 goto lock_mmap; 1332 1333 if (unlikely(access_error(error_code, vma))) { 1334 bad_area_access_error(regs, error_code, address, NULL, vma); 1335 count_vm_vma_lock_event(VMA_LOCK_SUCCESS); 1336 return; 1337 } 1338 fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs); 1339 if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED))) 1340 vma_end_read(vma); 1341 1342 if (!(fault & VM_FAULT_RETRY)) { 1343 count_vm_vma_lock_event(VMA_LOCK_SUCCESS); 1344 goto done; 1345 } 1346 count_vm_vma_lock_event(VMA_LOCK_RETRY); 1347 if (fault & VM_FAULT_MAJOR) 1348 flags |= FAULT_FLAG_TRIED; 1349 1350 /* Quick path to respond to signals */ 1351 if (fault_signal_pending(fault, regs)) { 1352 if (!user_mode(regs)) 1353 kernelmode_fixup_or_oops(regs, error_code, address, 1354 SIGBUS, BUS_ADRERR, 1355 ARCH_DEFAULT_PKEY); 1356 return; 1357 } 1358 lock_mmap: 1359 1360 retry: 1361 vma = lock_mm_and_find_vma(mm, address, regs); 1362 if (unlikely(!vma)) { 1363 bad_area_nosemaphore(regs, error_code, address); 1364 return; 1365 } 1366 1367 /* 1368 * Ok, we have a good vm_area for this memory access, so 1369 * we can handle it.. 1370 */ 1371 if (unlikely(access_error(error_code, vma))) { 1372 bad_area_access_error(regs, error_code, address, mm, vma); 1373 return; 1374 } 1375 1376 /* 1377 * If for any reason at all we couldn't handle the fault, 1378 * make sure we exit gracefully rather than endlessly redo 1379 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if 1380 * we get VM_FAULT_RETRY back, the mmap_lock has been unlocked. 1381 * 1382 * Note that handle_userfault() may also release and reacquire mmap_lock 1383 * (and not return with VM_FAULT_RETRY), when returning to userland to 1384 * repeat the page fault later with a VM_FAULT_NOPAGE retval 1385 * (potentially after handling any pending signal during the return to 1386 * userland). The return to userland is identified whenever 1387 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags. 1388 */ 1389 fault = handle_mm_fault(vma, address, flags, regs); 1390 1391 if (fault_signal_pending(fault, regs)) { 1392 /* 1393 * Quick path to respond to signals. The core mm code 1394 * has unlocked the mm for us if we get here. 1395 */ 1396 if (!user_mode(regs)) 1397 kernelmode_fixup_or_oops(regs, error_code, address, 1398 SIGBUS, BUS_ADRERR, 1399 ARCH_DEFAULT_PKEY); 1400 return; 1401 } 1402 1403 /* The fault is fully completed (including releasing mmap lock) */ 1404 if (fault & VM_FAULT_COMPLETED) 1405 return; 1406 1407 /* 1408 * If we need to retry the mmap_lock has already been released, 1409 * and if there is a fatal signal pending there is no guarantee 1410 * that we made any progress. Handle this case first. 1411 */ 1412 if (unlikely(fault & VM_FAULT_RETRY)) { 1413 flags |= FAULT_FLAG_TRIED; 1414 goto retry; 1415 } 1416 1417 mmap_read_unlock(mm); 1418 done: 1419 if (likely(!(fault & VM_FAULT_ERROR))) 1420 return; 1421 1422 if (fatal_signal_pending(current) && !user_mode(regs)) { 1423 kernelmode_fixup_or_oops(regs, error_code, address, 1424 0, 0, ARCH_DEFAULT_PKEY); 1425 return; 1426 } 1427 1428 if (fault & VM_FAULT_OOM) { 1429 /* Kernel mode? Handle exceptions or die: */ 1430 if (!user_mode(regs)) { 1431 kernelmode_fixup_or_oops(regs, error_code, address, 1432 SIGSEGV, SEGV_MAPERR, 1433 ARCH_DEFAULT_PKEY); 1434 return; 1435 } 1436 1437 /* 1438 * We ran out of memory, call the OOM killer, and return the 1439 * userspace (which will retry the fault, or kill us if we got 1440 * oom-killed): 1441 */ 1442 pagefault_out_of_memory(); 1443 } else { 1444 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| 1445 VM_FAULT_HWPOISON_LARGE)) 1446 do_sigbus(regs, error_code, address, fault); 1447 else if (fault & VM_FAULT_SIGSEGV) 1448 bad_area_nosemaphore(regs, error_code, address); 1449 else 1450 BUG(); 1451 } 1452 } 1453 NOKPROBE_SYMBOL(do_user_addr_fault); 1454 1455 static __always_inline void 1456 trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code, 1457 unsigned long address) 1458 { 1459 if (user_mode(regs)) 1460 trace_page_fault_user(address, regs, error_code); 1461 else 1462 trace_page_fault_kernel(address, regs, error_code); 1463 } 1464 1465 static __always_inline void 1466 handle_page_fault(struct pt_regs *regs, unsigned long error_code, 1467 unsigned long address) 1468 { 1469 trace_page_fault_entries(regs, error_code, address); 1470 1471 if (unlikely(kmmio_fault(regs, address))) 1472 return; 1473 1474 /* Was the fault on kernel-controlled part of the address space? */ 1475 if (unlikely(fault_in_kernel_space(address))) { 1476 do_kern_addr_fault(regs, error_code, address); 1477 } else { 1478 do_user_addr_fault(regs, error_code, address); 1479 } 1480 /* 1481 * page fault handling might have reenabled interrupts, 1482 * make sure to disable them again. 1483 */ 1484 local_irq_disable(); 1485 } 1486 1487 DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault) 1488 { 1489 irqentry_state_t state; 1490 unsigned long address; 1491 1492 address = cpu_feature_enabled(X86_FEATURE_FRED) ? fred_event_data(regs) : read_cr2(); 1493 1494 /* 1495 * KVM uses #PF vector to deliver 'page not present' events to guests 1496 * (asynchronous page fault mechanism). The event happens when a 1497 * userspace task is trying to access some valid (from guest's point of 1498 * view) memory which is not currently mapped by the host (e.g. the 1499 * memory is swapped out). Note, the corresponding "page ready" event 1500 * which is injected when the memory becomes available, is delivered via 1501 * an interrupt mechanism and not a #PF exception 1502 * (see arch/x86/kernel/kvm.c: sysvec_kvm_asyncpf_interrupt()). 1503 * 1504 * We are relying on the interrupted context being sane (valid RSP, 1505 * relevant locks not held, etc.), which is fine as long as the 1506 * interrupted context had IF=1. We are also relying on the KVM 1507 * async pf type field and CR2 being read consistently instead of 1508 * getting values from real and async page faults mixed up. 1509 * 1510 * Fingers crossed. 1511 * 1512 * The async #PF handling code takes care of idtentry handling 1513 * itself. 1514 */ 1515 if (kvm_handle_async_pf(regs, (u32)address)) 1516 return; 1517 1518 /* 1519 * Entry handling for valid #PF from kernel mode is slightly 1520 * different: RCU is already watching and ct_irq_enter() must not 1521 * be invoked because a kernel fault on a user space address might 1522 * sleep. 1523 * 1524 * In case the fault hit a RCU idle region the conditional entry 1525 * code reenabled RCU to avoid subsequent wreckage which helps 1526 * debuggability. 1527 */ 1528 state = irqentry_enter(regs); 1529 1530 instrumentation_begin(); 1531 handle_page_fault(regs, error_code, address); 1532 instrumentation_end(); 1533 1534 irqentry_exit(regs, state); 1535 } 1536