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/extable.h> /* search_exception_tables */ 11#include <linux/memblock.h> /* max_low_pfn */ 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/prefetch.h> /* prefetchw */ 18#include <linux/context_tracking.h> /* exception_enter(), ... */ 19#include <linux/uaccess.h> /* faulthandler_disabled() */ 20#include <linux/efi.h> /* efi_crash_gracefully_on_page_fault()*/ 21#include <linux/mm_types.h> 22#include <linux/mm.h> /* find_and_lock_vma() */ 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 <asm/trace/exceptions.h> 42 43/* 44 * Returns 0 if mmiotrace is disabled, or if the fault is not 45 * handled by mmiotrace: 46 */ 47static nokprobe_inline int 48kmmio_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 */ 71static inline int 72check_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 114static 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 123static int 124is_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 172DEFINE_SPINLOCK(pgd_lock); 173LIST_HEAD(pgd_list); 174 175#ifdef CONFIG_X86_32 176static 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 */ 233static 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} 264NOKPROBE_SYMBOL(vmalloc_fault); 265 266void 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 290static bool low_pfn(unsigned long pfn) 291{ 292 return pfn < max_low_pfn; 293} 294 295static 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)); 329out: 330 pr_cont("\n"); 331} 332 333#else /* CONFIG_X86_64: */ 334 335#ifdef CONFIG_CPU_SUP_AMD 336static const char errata93_warning[] = 337KERN_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 344static int bad_address(void *p) 345{ 346 unsigned long dummy; 347 348 return get_kernel_nofault(dummy, (unsigned long *)p); 349} 350 351static 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)); 397out: 398 pr_cont("\n"); 399 return; 400bad: 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 */ 420static 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 */ 455static 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: */ 465static 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 478static 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 509static void 510show_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 pgd_t *pgd; 518 pte_t *pte; 519 520 pgd = __va(read_cr3_pa()); 521 pgd += pgd_index(address); 522 523 pte = lookup_address_in_pgd(pgd, address, &level); 524 525 if (pte && pte_present(*pte) && !pte_exec(*pte)) 526 pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n", 527 from_kuid(&init_user_ns, current_uid())); 528 if (pte && pte_present(*pte) && pte_exec(*pte) && 529 (pgd_flags(*pgd) & _PAGE_USER) && 530 (__read_cr4() & X86_CR4_SMEP)) 531 pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n", 532 from_kuid(&init_user_ns, current_uid())); 533 } 534 535 if (address < PAGE_SIZE && !user_mode(regs)) 536 pr_alert("BUG: kernel NULL pointer dereference, address: %px\n", 537 (void *)address); 538 else 539 pr_alert("BUG: unable to handle page fault for address: %px\n", 540 (void *)address); 541 542 pr_alert("#PF: %s %s in %s mode\n", 543 (error_code & X86_PF_USER) ? "user" : "supervisor", 544 (error_code & X86_PF_INSTR) ? "instruction fetch" : 545 (error_code & X86_PF_WRITE) ? "write access" : 546 "read access", 547 user_mode(regs) ? "user" : "kernel"); 548 pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code, 549 !(error_code & X86_PF_PROT) ? "not-present page" : 550 (error_code & X86_PF_RSVD) ? "reserved bit violation" : 551 (error_code & X86_PF_PK) ? "protection keys violation" : 552 (error_code & X86_PF_RMP) ? "RMP violation" : 553 "permissions violation"); 554 555 if (!(error_code & X86_PF_USER) && user_mode(regs)) { 556 struct desc_ptr idt, gdt; 557 u16 ldtr, tr; 558 559 /* 560 * This can happen for quite a few reasons. The more obvious 561 * ones are faults accessing the GDT, or LDT. Perhaps 562 * surprisingly, if the CPU tries to deliver a benign or 563 * contributory exception from user code and gets a page fault 564 * during delivery, the page fault can be delivered as though 565 * it originated directly from user code. This could happen 566 * due to wrong permissions on the IDT, GDT, LDT, TSS, or 567 * kernel or IST stack. 568 */ 569 store_idt(&idt); 570 571 /* Usable even on Xen PV -- it's just slow. */ 572 native_store_gdt(&gdt); 573 574 pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n", 575 idt.address, idt.size, gdt.address, gdt.size); 576 577 store_ldt(ldtr); 578 show_ldttss(&gdt, "LDTR", ldtr); 579 580 store_tr(tr); 581 show_ldttss(&gdt, "TR", tr); 582 } 583 584 dump_pagetable(address); 585 586 if (error_code & X86_PF_RMP) 587 snp_dump_hva_rmpentry(address); 588} 589 590static noinline void 591pgtable_bad(struct pt_regs *regs, unsigned long error_code, 592 unsigned long address) 593{ 594 struct task_struct *tsk; 595 unsigned long flags; 596 int sig; 597 598 flags = oops_begin(); 599 tsk = current; 600 sig = SIGKILL; 601 602 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", 603 tsk->comm, address); 604 dump_pagetable(address); 605 606 if (__die("Bad pagetable", regs, error_code)) 607 sig = 0; 608 609 oops_end(flags, regs, sig); 610} 611 612static void sanitize_error_code(unsigned long address, 613 unsigned long *error_code) 614{ 615 /* 616 * To avoid leaking information about the kernel page 617 * table layout, pretend that user-mode accesses to 618 * kernel addresses are always protection faults. 619 * 620 * NB: This means that failed vsyscalls with vsyscall=none 621 * will have the PROT bit. This doesn't leak any 622 * information and does not appear to cause any problems. 623 */ 624 if (address >= TASK_SIZE_MAX) 625 *error_code |= X86_PF_PROT; 626} 627 628static void set_signal_archinfo(unsigned long address, 629 unsigned long error_code) 630{ 631 struct task_struct *tsk = current; 632 633 tsk->thread.trap_nr = X86_TRAP_PF; 634 tsk->thread.error_code = error_code | X86_PF_USER; 635 tsk->thread.cr2 = address; 636} 637 638static noinline void 639page_fault_oops(struct pt_regs *regs, unsigned long error_code, 640 unsigned long address) 641{ 642#ifdef CONFIG_VMAP_STACK 643 struct stack_info info; 644#endif 645 unsigned long flags; 646 int sig; 647 648 if (user_mode(regs)) { 649 /* 650 * Implicit kernel access from user mode? Skip the stack 651 * overflow and EFI special cases. 652 */ 653 goto oops; 654 } 655 656#ifdef CONFIG_VMAP_STACK 657 /* 658 * Stack overflow? During boot, we can fault near the initial 659 * stack in the direct map, but that's not an overflow -- check 660 * that we're in vmalloc space to avoid this. 661 */ 662 if (is_vmalloc_addr((void *)address) && 663 get_stack_guard_info((void *)address, &info)) { 664 /* 665 * We're likely to be running with very little stack space 666 * left. It's plausible that we'd hit this condition but 667 * double-fault even before we get this far, in which case 668 * we're fine: the double-fault handler will deal with it. 669 * 670 * We don't want to make it all the way into the oops code 671 * and then double-fault, though, because we're likely to 672 * break the console driver and lose most of the stack dump. 673 */ 674 call_on_stack(__this_cpu_ist_top_va(DF) - sizeof(void*), 675 handle_stack_overflow, 676 ASM_CALL_ARG3, 677 , [arg1] "r" (regs), [arg2] "r" (address), [arg3] "r" (&info)); 678 679 unreachable(); 680 } 681#endif 682 683 /* 684 * Buggy firmware could access regions which might page fault. If 685 * this happens, EFI has a special OOPS path that will try to 686 * avoid hanging the system. 687 */ 688 if (IS_ENABLED(CONFIG_EFI)) 689 efi_crash_gracefully_on_page_fault(address); 690 691 /* Only not-present faults should be handled by KFENCE. */ 692 if (!(error_code & X86_PF_PROT) && 693 kfence_handle_page_fault(address, error_code & X86_PF_WRITE, regs)) 694 return; 695 696oops: 697 /* 698 * Oops. The kernel tried to access some bad page. We'll have to 699 * terminate things with extreme prejudice: 700 */ 701 flags = oops_begin(); 702 703 show_fault_oops(regs, error_code, address); 704 705 if (task_stack_end_corrupted(current)) 706 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); 707 708 sig = SIGKILL; 709 if (__die("Oops", regs, error_code)) 710 sig = 0; 711 712 /* Executive summary in case the body of the oops scrolled away */ 713 printk(KERN_DEFAULT "CR2: %016lx\n", address); 714 715 oops_end(flags, regs, sig); 716} 717 718static noinline void 719kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code, 720 unsigned long address, int signal, int si_code, 721 u32 pkey) 722{ 723 WARN_ON_ONCE(user_mode(regs)); 724 725 /* Are we prepared to handle this kernel fault? */ 726 if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) { 727 /* 728 * Any interrupt that takes a fault gets the fixup. This makes 729 * the below recursive fault logic only apply to a faults from 730 * task context. 731 */ 732 if (in_interrupt()) 733 return; 734 735 /* 736 * Per the above we're !in_interrupt(), aka. task context. 737 * 738 * In this case we need to make sure we're not recursively 739 * faulting through the emulate_vsyscall() logic. 740 */ 741 if (current->thread.sig_on_uaccess_err && signal) { 742 sanitize_error_code(address, &error_code); 743 744 set_signal_archinfo(address, error_code); 745 746 if (si_code == SEGV_PKUERR) { 747 force_sig_pkuerr((void __user *)address, pkey); 748 } else { 749 /* XXX: hwpoison faults will set the wrong code. */ 750 force_sig_fault(signal, si_code, (void __user *)address); 751 } 752 } 753 754 /* 755 * Barring that, we can do the fixup and be happy. 756 */ 757 return; 758 } 759 760 /* 761 * AMD erratum #91 manifests as a spurious page fault on a PREFETCH 762 * instruction. 763 */ 764 if (is_prefetch(regs, error_code, address)) 765 return; 766 767 page_fault_oops(regs, error_code, address); 768} 769 770/* 771 * Print out info about fatal segfaults, if the show_unhandled_signals 772 * sysctl is set: 773 */ 774static inline void 775show_signal_msg(struct pt_regs *regs, unsigned long error_code, 776 unsigned long address, struct task_struct *tsk) 777{ 778 const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG; 779 /* This is a racy snapshot, but it's better than nothing. */ 780 int cpu = raw_smp_processor_id(); 781 782 if (!unhandled_signal(tsk, SIGSEGV)) 783 return; 784 785 if (!printk_ratelimit()) 786 return; 787 788 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx", 789 loglvl, tsk->comm, task_pid_nr(tsk), address, 790 (void *)regs->ip, (void *)regs->sp, error_code); 791 792 print_vma_addr(KERN_CONT " in ", regs->ip); 793 794 /* 795 * Dump the likely CPU where the fatal segfault happened. 796 * This can help identify faulty hardware. 797 */ 798 printk(KERN_CONT " likely on CPU %d (core %d, socket %d)", cpu, 799 topology_core_id(cpu), topology_physical_package_id(cpu)); 800 801 802 printk(KERN_CONT "\n"); 803 804 show_opcodes(regs, loglvl); 805} 806 807static void 808__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 809 unsigned long address, u32 pkey, int si_code) 810{ 811 struct task_struct *tsk = current; 812 813 if (!user_mode(regs)) { 814 kernelmode_fixup_or_oops(regs, error_code, address, 815 SIGSEGV, si_code, pkey); 816 return; 817 } 818 819 if (!(error_code & X86_PF_USER)) { 820 /* Implicit user access to kernel memory -- just oops */ 821 page_fault_oops(regs, error_code, address); 822 return; 823 } 824 825 /* 826 * User mode accesses just cause a SIGSEGV. 827 * It's possible to have interrupts off here: 828 */ 829 local_irq_enable(); 830 831 /* 832 * Valid to do another page fault here because this one came 833 * from user space: 834 */ 835 if (is_prefetch(regs, error_code, address)) 836 return; 837 838 if (is_errata100(regs, address)) 839 return; 840 841 sanitize_error_code(address, &error_code); 842 843 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address)) 844 return; 845 846 if (likely(show_unhandled_signals)) 847 show_signal_msg(regs, error_code, address, tsk); 848 849 set_signal_archinfo(address, error_code); 850 851 if (si_code == SEGV_PKUERR) 852 force_sig_pkuerr((void __user *)address, pkey); 853 else 854 force_sig_fault(SIGSEGV, si_code, (void __user *)address); 855 856 local_irq_disable(); 857} 858 859static noinline void 860bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 861 unsigned long address) 862{ 863 __bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR); 864} 865 866static void 867__bad_area(struct pt_regs *regs, unsigned long error_code, 868 unsigned long address, u32 pkey, int si_code) 869{ 870 struct mm_struct *mm = current->mm; 871 /* 872 * Something tried to access memory that isn't in our memory map.. 873 * Fix it, but check if it's kernel or user first.. 874 */ 875 mmap_read_unlock(mm); 876 877 __bad_area_nosemaphore(regs, error_code, address, pkey, si_code); 878} 879 880static inline bool bad_area_access_from_pkeys(unsigned long error_code, 881 struct vm_area_struct *vma) 882{ 883 /* This code is always called on the current mm */ 884 bool foreign = false; 885 886 if (!cpu_feature_enabled(X86_FEATURE_OSPKE)) 887 return false; 888 if (error_code & X86_PF_PK) 889 return true; 890 /* this checks permission keys on the VMA: */ 891 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE), 892 (error_code & X86_PF_INSTR), foreign)) 893 return true; 894 return false; 895} 896 897static noinline void 898bad_area_access_error(struct pt_regs *regs, unsigned long error_code, 899 unsigned long address, struct vm_area_struct *vma) 900{ 901 /* 902 * This OSPKE check is not strictly necessary at runtime. 903 * But, doing it this way allows compiler optimizations 904 * if pkeys are compiled out. 905 */ 906 if (bad_area_access_from_pkeys(error_code, vma)) { 907 /* 908 * A protection key fault means that the PKRU value did not allow 909 * access to some PTE. Userspace can figure out what PKRU was 910 * from the XSAVE state. This function captures the pkey from 911 * the vma and passes it to userspace so userspace can discover 912 * which protection key was set on the PTE. 913 * 914 * If we get here, we know that the hardware signaled a X86_PF_PK 915 * fault and that there was a VMA once we got in the fault 916 * handler. It does *not* guarantee that the VMA we find here 917 * was the one that we faulted on. 918 * 919 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4); 920 * 2. T1 : set PKRU to deny access to pkey=4, touches page 921 * 3. T1 : faults... 922 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5); 923 * 5. T1 : enters fault handler, takes mmap_lock, etc... 924 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really 925 * faulted on a pte with its pkey=4. 926 */ 927 u32 pkey = vma_pkey(vma); 928 929 __bad_area(regs, error_code, address, pkey, SEGV_PKUERR); 930 } else { 931 __bad_area(regs, error_code, address, 0, SEGV_ACCERR); 932 } 933} 934 935static void 936do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, 937 vm_fault_t fault) 938{ 939 /* Kernel mode? Handle exceptions or die: */ 940 if (!user_mode(regs)) { 941 kernelmode_fixup_or_oops(regs, error_code, address, 942 SIGBUS, BUS_ADRERR, ARCH_DEFAULT_PKEY); 943 return; 944 } 945 946 /* User-space => ok to do another page fault: */ 947 if (is_prefetch(regs, error_code, address)) 948 return; 949 950 sanitize_error_code(address, &error_code); 951 952 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address)) 953 return; 954 955 set_signal_archinfo(address, error_code); 956 957#ifdef CONFIG_MEMORY_FAILURE 958 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { 959 struct task_struct *tsk = current; 960 unsigned lsb = 0; 961 962 pr_err( 963 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", 964 tsk->comm, tsk->pid, address); 965 if (fault & VM_FAULT_HWPOISON_LARGE) 966 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 967 if (fault & VM_FAULT_HWPOISON) 968 lsb = PAGE_SHIFT; 969 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb); 970 return; 971 } 972#endif 973 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address); 974} 975 976static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte) 977{ 978 if ((error_code & X86_PF_WRITE) && !pte_write(*pte)) 979 return 0; 980 981 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte)) 982 return 0; 983 984 return 1; 985} 986 987/* 988 * Handle a spurious fault caused by a stale TLB entry. 989 * 990 * This allows us to lazily refresh the TLB when increasing the 991 * permissions of a kernel page (RO -> RW or NX -> X). Doing it 992 * eagerly is very expensive since that implies doing a full 993 * cross-processor TLB flush, even if no stale TLB entries exist 994 * on other processors. 995 * 996 * Spurious faults may only occur if the TLB contains an entry with 997 * fewer permission than the page table entry. Non-present (P = 0) 998 * and reserved bit (R = 1) faults are never spurious. 999 * 1000 * There are no security implications to leaving a stale TLB when 1001 * increasing the permissions on a page. 1002 * 1003 * Returns non-zero if a spurious fault was handled, zero otherwise. 1004 * 1005 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3 1006 * (Optional Invalidation). 1007 */ 1008static noinline int 1009spurious_kernel_fault(unsigned long error_code, unsigned long address) 1010{ 1011 pgd_t *pgd; 1012 p4d_t *p4d; 1013 pud_t *pud; 1014 pmd_t *pmd; 1015 pte_t *pte; 1016 int ret; 1017 1018 /* 1019 * Only writes to RO or instruction fetches from NX may cause 1020 * spurious faults. 1021 * 1022 * These could be from user or supervisor accesses but the TLB 1023 * is only lazily flushed after a kernel mapping protection 1024 * change, so user accesses are not expected to cause spurious 1025 * faults. 1026 */ 1027 if (error_code != (X86_PF_WRITE | X86_PF_PROT) && 1028 error_code != (X86_PF_INSTR | X86_PF_PROT)) 1029 return 0; 1030 1031 pgd = init_mm.pgd + pgd_index(address); 1032 if (!pgd_present(*pgd)) 1033 return 0; 1034 1035 p4d = p4d_offset(pgd, address); 1036 if (!p4d_present(*p4d)) 1037 return 0; 1038 1039 if (p4d_leaf(*p4d)) 1040 return spurious_kernel_fault_check(error_code, (pte_t *) p4d); 1041 1042 pud = pud_offset(p4d, address); 1043 if (!pud_present(*pud)) 1044 return 0; 1045 1046 if (pud_leaf(*pud)) 1047 return spurious_kernel_fault_check(error_code, (pte_t *) pud); 1048 1049 pmd = pmd_offset(pud, address); 1050 if (!pmd_present(*pmd)) 1051 return 0; 1052 1053 if (pmd_leaf(*pmd)) 1054 return spurious_kernel_fault_check(error_code, (pte_t *) pmd); 1055 1056 pte = pte_offset_kernel(pmd, address); 1057 if (!pte_present(*pte)) 1058 return 0; 1059 1060 ret = spurious_kernel_fault_check(error_code, pte); 1061 if (!ret) 1062 return 0; 1063 1064 /* 1065 * Make sure we have permissions in PMD. 1066 * If not, then there's a bug in the page tables: 1067 */ 1068 ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd); 1069 WARN_ONCE(!ret, "PMD has incorrect permission bits\n"); 1070 1071 return ret; 1072} 1073NOKPROBE_SYMBOL(spurious_kernel_fault); 1074 1075int show_unhandled_signals = 1; 1076 1077static inline int 1078access_error(unsigned long error_code, struct vm_area_struct *vma) 1079{ 1080 /* This is only called for the current mm, so: */ 1081 bool foreign = false; 1082 1083 /* 1084 * Read or write was blocked by protection keys. This is 1085 * always an unconditional error and can never result in 1086 * a follow-up action to resolve the fault, like a COW. 1087 */ 1088 if (error_code & X86_PF_PK) 1089 return 1; 1090 1091 /* 1092 * SGX hardware blocked the access. This usually happens 1093 * when the enclave memory contents have been destroyed, like 1094 * after a suspend/resume cycle. In any case, the kernel can't 1095 * fix the cause of the fault. Handle the fault as an access 1096 * error even in cases where no actual access violation 1097 * occurred. This allows userspace to rebuild the enclave in 1098 * response to the signal. 1099 */ 1100 if (unlikely(error_code & X86_PF_SGX)) 1101 return 1; 1102 1103 /* 1104 * Make sure to check the VMA so that we do not perform 1105 * faults just to hit a X86_PF_PK as soon as we fill in a 1106 * page. 1107 */ 1108 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE), 1109 (error_code & X86_PF_INSTR), foreign)) 1110 return 1; 1111 1112 /* 1113 * Shadow stack accesses (PF_SHSTK=1) are only permitted to 1114 * shadow stack VMAs. All other accesses result in an error. 1115 */ 1116 if (error_code & X86_PF_SHSTK) { 1117 if (unlikely(!(vma->vm_flags & VM_SHADOW_STACK))) 1118 return 1; 1119 if (unlikely(!(vma->vm_flags & VM_WRITE))) 1120 return 1; 1121 return 0; 1122 } 1123 1124 if (error_code & X86_PF_WRITE) { 1125 /* write, present and write, not present: */ 1126 if (unlikely(vma->vm_flags & VM_SHADOW_STACK)) 1127 return 1; 1128 if (unlikely(!(vma->vm_flags & VM_WRITE))) 1129 return 1; 1130 return 0; 1131 } 1132 1133 /* read, present: */ 1134 if (unlikely(error_code & X86_PF_PROT)) 1135 return 1; 1136 1137 /* read, not present: */ 1138 if (unlikely(!vma_is_accessible(vma))) 1139 return 1; 1140 1141 return 0; 1142} 1143 1144bool fault_in_kernel_space(unsigned long address) 1145{ 1146 /* 1147 * On 64-bit systems, the vsyscall page is at an address above 1148 * TASK_SIZE_MAX, but is not considered part of the kernel 1149 * address space. 1150 */ 1151 if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address)) 1152 return false; 1153 1154 return address >= TASK_SIZE_MAX; 1155} 1156 1157/* 1158 * Called for all faults where 'address' is part of the kernel address 1159 * space. Might get called for faults that originate from *code* that 1160 * ran in userspace or the kernel. 1161 */ 1162static void 1163do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code, 1164 unsigned long address) 1165{ 1166 /* 1167 * Protection keys exceptions only happen on user pages. We 1168 * have no user pages in the kernel portion of the address 1169 * space, so do not expect them here. 1170 */ 1171 WARN_ON_ONCE(hw_error_code & X86_PF_PK); 1172 1173#ifdef CONFIG_X86_32 1174 /* 1175 * We can fault-in kernel-space virtual memory on-demand. The 1176 * 'reference' page table is init_mm.pgd. 1177 * 1178 * NOTE! We MUST NOT take any locks for this case. We may 1179 * be in an interrupt or a critical region, and should 1180 * only copy the information from the master page table, 1181 * nothing more. 1182 * 1183 * Before doing this on-demand faulting, ensure that the 1184 * fault is not any of the following: 1185 * 1. A fault on a PTE with a reserved bit set. 1186 * 2. A fault caused by a user-mode access. (Do not demand- 1187 * fault kernel memory due to user-mode accesses). 1188 * 3. A fault caused by a page-level protection violation. 1189 * (A demand fault would be on a non-present page which 1190 * would have X86_PF_PROT==0). 1191 * 1192 * This is only needed to close a race condition on x86-32 in 1193 * the vmalloc mapping/unmapping code. See the comment above 1194 * vmalloc_fault() for details. On x86-64 the race does not 1195 * exist as the vmalloc mappings don't need to be synchronized 1196 * there. 1197 */ 1198 if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) { 1199 if (vmalloc_fault(address) >= 0) 1200 return; 1201 } 1202#endif 1203 1204 if (is_f00f_bug(regs, hw_error_code, address)) 1205 return; 1206 1207 /* Was the fault spurious, caused by lazy TLB invalidation? */ 1208 if (spurious_kernel_fault(hw_error_code, address)) 1209 return; 1210 1211 /* kprobes don't want to hook the spurious faults: */ 1212 if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF))) 1213 return; 1214 1215 /* 1216 * Note, despite being a "bad area", there are quite a few 1217 * acceptable reasons to get here, such as erratum fixups 1218 * and handling kernel code that can fault, like get_user(). 1219 * 1220 * Don't take the mm semaphore here. If we fixup a prefetch 1221 * fault we could otherwise deadlock: 1222 */ 1223 bad_area_nosemaphore(regs, hw_error_code, address); 1224} 1225NOKPROBE_SYMBOL(do_kern_addr_fault); 1226 1227/* 1228 * Handle faults in the user portion of the address space. Nothing in here 1229 * should check X86_PF_USER without a specific justification: for almost 1230 * all purposes, we should treat a normal kernel access to user memory 1231 * (e.g. get_user(), put_user(), etc.) the same as the WRUSS instruction. 1232 * The one exception is AC flag handling, which is, per the x86 1233 * architecture, special for WRUSS. 1234 */ 1235static inline 1236void do_user_addr_fault(struct pt_regs *regs, 1237 unsigned long error_code, 1238 unsigned long address) 1239{ 1240 struct vm_area_struct *vma; 1241 struct task_struct *tsk; 1242 struct mm_struct *mm; 1243 vm_fault_t fault; 1244 unsigned int flags = FAULT_FLAG_DEFAULT; 1245 1246 tsk = current; 1247 mm = tsk->mm; 1248 1249 if (unlikely((error_code & (X86_PF_USER | X86_PF_INSTR)) == X86_PF_INSTR)) { 1250 /* 1251 * Whoops, this is kernel mode code trying to execute from 1252 * user memory. Unless this is AMD erratum #93, which 1253 * corrupts RIP such that it looks like a user address, 1254 * this is unrecoverable. Don't even try to look up the 1255 * VMA or look for extable entries. 1256 */ 1257 if (is_errata93(regs, address)) 1258 return; 1259 1260 page_fault_oops(regs, error_code, address); 1261 return; 1262 } 1263 1264 /* kprobes don't want to hook the spurious faults: */ 1265 if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF))) 1266 return; 1267 1268 /* 1269 * Reserved bits are never expected to be set on 1270 * entries in the user portion of the page tables. 1271 */ 1272 if (unlikely(error_code & X86_PF_RSVD)) 1273 pgtable_bad(regs, error_code, address); 1274 1275 /* 1276 * If SMAP is on, check for invalid kernel (supervisor) access to user 1277 * pages in the user address space. The odd case here is WRUSS, 1278 * which, according to the preliminary documentation, does not respect 1279 * SMAP and will have the USER bit set so, in all cases, SMAP 1280 * enforcement appears to be consistent with the USER bit. 1281 */ 1282 if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) && 1283 !(error_code & X86_PF_USER) && 1284 !(regs->flags & X86_EFLAGS_AC))) { 1285 /* 1286 * No extable entry here. This was a kernel access to an 1287 * invalid pointer. get_kernel_nofault() will not get here. 1288 */ 1289 page_fault_oops(regs, error_code, address); 1290 return; 1291 } 1292 1293 /* 1294 * If we're in an interrupt, have no user context or are running 1295 * in a region with pagefaults disabled then we must not take the fault 1296 */ 1297 if (unlikely(faulthandler_disabled() || !mm)) { 1298 bad_area_nosemaphore(regs, error_code, address); 1299 return; 1300 } 1301 1302 /* Legacy check - remove this after verifying that it doesn't trigger */ 1303 if (WARN_ON_ONCE(!(regs->flags & X86_EFLAGS_IF))) { 1304 bad_area_nosemaphore(regs, error_code, address); 1305 return; 1306 } 1307 1308 local_irq_enable(); 1309 1310 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 1311 1312 /* 1313 * Read-only permissions can not be expressed in shadow stack PTEs. 1314 * Treat all shadow stack accesses as WRITE faults. This ensures 1315 * that the MM will prepare everything (e.g., break COW) such that 1316 * maybe_mkwrite() can create a proper shadow stack PTE. 1317 */ 1318 if (error_code & X86_PF_SHSTK) 1319 flags |= FAULT_FLAG_WRITE; 1320 if (error_code & X86_PF_WRITE) 1321 flags |= FAULT_FLAG_WRITE; 1322 if (error_code & X86_PF_INSTR) 1323 flags |= FAULT_FLAG_INSTRUCTION; 1324 1325 /* 1326 * We set FAULT_FLAG_USER based on the register state, not 1327 * based on X86_PF_USER. User space accesses that cause 1328 * system page faults are still user accesses. 1329 */ 1330 if (user_mode(regs)) 1331 flags |= FAULT_FLAG_USER; 1332 1333#ifdef CONFIG_X86_64 1334 /* 1335 * Faults in the vsyscall page might need emulation. The 1336 * vsyscall page is at a high address (>PAGE_OFFSET), but is 1337 * considered to be part of the user address space. 1338 * 1339 * The vsyscall page does not have a "real" VMA, so do this 1340 * emulation before we go searching for VMAs. 1341 * 1342 * PKRU never rejects instruction fetches, so we don't need 1343 * to consider the PF_PK bit. 1344 */ 1345 if (is_vsyscall_vaddr(address)) { 1346 if (emulate_vsyscall(error_code, regs, address)) 1347 return; 1348 } 1349#endif 1350 1351 if (!(flags & FAULT_FLAG_USER)) 1352 goto lock_mmap; 1353 1354 vma = lock_vma_under_rcu(mm, address); 1355 if (!vma) 1356 goto lock_mmap; 1357 1358 if (unlikely(access_error(error_code, vma))) { 1359 vma_end_read(vma); 1360 goto lock_mmap; 1361 } 1362 fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs); 1363 if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED))) 1364 vma_end_read(vma); 1365 1366 if (!(fault & VM_FAULT_RETRY)) { 1367 count_vm_vma_lock_event(VMA_LOCK_SUCCESS); 1368 goto done; 1369 } 1370 count_vm_vma_lock_event(VMA_LOCK_RETRY); 1371 if (fault & VM_FAULT_MAJOR) 1372 flags |= FAULT_FLAG_TRIED; 1373 1374 /* Quick path to respond to signals */ 1375 if (fault_signal_pending(fault, regs)) { 1376 if (!user_mode(regs)) 1377 kernelmode_fixup_or_oops(regs, error_code, address, 1378 SIGBUS, BUS_ADRERR, 1379 ARCH_DEFAULT_PKEY); 1380 return; 1381 } 1382lock_mmap: 1383 1384retry: 1385 vma = lock_mm_and_find_vma(mm, address, regs); 1386 if (unlikely(!vma)) { 1387 bad_area_nosemaphore(regs, error_code, address); 1388 return; 1389 } 1390 1391 /* 1392 * Ok, we have a good vm_area for this memory access, so 1393 * we can handle it.. 1394 */ 1395 if (unlikely(access_error(error_code, vma))) { 1396 bad_area_access_error(regs, error_code, address, vma); 1397 return; 1398 } 1399 1400 /* 1401 * If for any reason at all we couldn't handle the fault, 1402 * make sure we exit gracefully rather than endlessly redo 1403 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if 1404 * we get VM_FAULT_RETRY back, the mmap_lock has been unlocked. 1405 * 1406 * Note that handle_userfault() may also release and reacquire mmap_lock 1407 * (and not return with VM_FAULT_RETRY), when returning to userland to 1408 * repeat the page fault later with a VM_FAULT_NOPAGE retval 1409 * (potentially after handling any pending signal during the return to 1410 * userland). The return to userland is identified whenever 1411 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags. 1412 */ 1413 fault = handle_mm_fault(vma, address, flags, regs); 1414 1415 if (fault_signal_pending(fault, regs)) { 1416 /* 1417 * Quick path to respond to signals. The core mm code 1418 * has unlocked the mm for us if we get here. 1419 */ 1420 if (!user_mode(regs)) 1421 kernelmode_fixup_or_oops(regs, error_code, address, 1422 SIGBUS, BUS_ADRERR, 1423 ARCH_DEFAULT_PKEY); 1424 return; 1425 } 1426 1427 /* The fault is fully completed (including releasing mmap lock) */ 1428 if (fault & VM_FAULT_COMPLETED) 1429 return; 1430 1431 /* 1432 * If we need to retry the mmap_lock has already been released, 1433 * and if there is a fatal signal pending there is no guarantee 1434 * that we made any progress. Handle this case first. 1435 */ 1436 if (unlikely(fault & VM_FAULT_RETRY)) { 1437 flags |= FAULT_FLAG_TRIED; 1438 goto retry; 1439 } 1440 1441 mmap_read_unlock(mm); 1442done: 1443 if (likely(!(fault & VM_FAULT_ERROR))) 1444 return; 1445 1446 if (fatal_signal_pending(current) && !user_mode(regs)) { 1447 kernelmode_fixup_or_oops(regs, error_code, address, 1448 0, 0, ARCH_DEFAULT_PKEY); 1449 return; 1450 } 1451 1452 if (fault & VM_FAULT_OOM) { 1453 /* Kernel mode? Handle exceptions or die: */ 1454 if (!user_mode(regs)) { 1455 kernelmode_fixup_or_oops(regs, error_code, address, 1456 SIGSEGV, SEGV_MAPERR, 1457 ARCH_DEFAULT_PKEY); 1458 return; 1459 } 1460 1461 /* 1462 * We ran out of memory, call the OOM killer, and return the 1463 * userspace (which will retry the fault, or kill us if we got 1464 * oom-killed): 1465 */ 1466 pagefault_out_of_memory(); 1467 } else { 1468 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| 1469 VM_FAULT_HWPOISON_LARGE)) 1470 do_sigbus(regs, error_code, address, fault); 1471 else if (fault & VM_FAULT_SIGSEGV) 1472 bad_area_nosemaphore(regs, error_code, address); 1473 else 1474 BUG(); 1475 } 1476} 1477NOKPROBE_SYMBOL(do_user_addr_fault); 1478 1479static __always_inline void 1480trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code, 1481 unsigned long address) 1482{ 1483 if (!trace_pagefault_enabled()) 1484 return; 1485 1486 if (user_mode(regs)) 1487 trace_page_fault_user(address, regs, error_code); 1488 else 1489 trace_page_fault_kernel(address, regs, error_code); 1490} 1491 1492static __always_inline void 1493handle_page_fault(struct pt_regs *regs, unsigned long error_code, 1494 unsigned long address) 1495{ 1496 trace_page_fault_entries(regs, error_code, address); 1497 1498 if (unlikely(kmmio_fault(regs, address))) 1499 return; 1500 1501 /* Was the fault on kernel-controlled part of the address space? */ 1502 if (unlikely(fault_in_kernel_space(address))) { 1503 do_kern_addr_fault(regs, error_code, address); 1504 } else { 1505 do_user_addr_fault(regs, error_code, address); 1506 /* 1507 * User address page fault handling might have reenabled 1508 * interrupts. Fixing up all potential exit points of 1509 * do_user_addr_fault() and its leaf functions is just not 1510 * doable w/o creating an unholy mess or turning the code 1511 * upside down. 1512 */ 1513 local_irq_disable(); 1514 } 1515} 1516 1517DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault) 1518{ 1519 irqentry_state_t state; 1520 unsigned long address; 1521 1522 address = cpu_feature_enabled(X86_FEATURE_FRED) ? fred_event_data(regs) : read_cr2(); 1523 1524 prefetchw(¤t->mm->mmap_lock); 1525 1526 /* 1527 * KVM uses #PF vector to deliver 'page not present' events to guests 1528 * (asynchronous page fault mechanism). The event happens when a 1529 * userspace task is trying to access some valid (from guest's point of 1530 * view) memory which is not currently mapped by the host (e.g. the 1531 * memory is swapped out). Note, the corresponding "page ready" event 1532 * which is injected when the memory becomes available, is delivered via 1533 * an interrupt mechanism and not a #PF exception 1534 * (see arch/x86/kernel/kvm.c: sysvec_kvm_asyncpf_interrupt()). 1535 * 1536 * We are relying on the interrupted context being sane (valid RSP, 1537 * relevant locks not held, etc.), which is fine as long as the 1538 * interrupted context had IF=1. We are also relying on the KVM 1539 * async pf type field and CR2 being read consistently instead of 1540 * getting values from real and async page faults mixed up. 1541 * 1542 * Fingers crossed. 1543 * 1544 * The async #PF handling code takes care of idtentry handling 1545 * itself. 1546 */ 1547 if (kvm_handle_async_pf(regs, (u32)address)) 1548 return; 1549 1550 /* 1551 * Entry handling for valid #PF from kernel mode is slightly 1552 * different: RCU is already watching and ct_irq_enter() must not 1553 * be invoked because a kernel fault on a user space address might 1554 * sleep. 1555 * 1556 * In case the fault hit a RCU idle region the conditional entry 1557 * code reenabled RCU to avoid subsequent wreckage which helps 1558 * debuggability. 1559 */ 1560 state = irqentry_enter(regs); 1561 1562 instrumentation_begin(); 1563 handle_page_fault(regs, error_code, address); 1564 instrumentation_end(); 1565 1566 irqentry_exit(regs, state); 1567} 1568