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 38 #define CREATE_TRACE_POINTS 39 #include <asm/trace/exceptions.h> 40 41 /* 42 * Returns 0 if mmiotrace is disabled, or if the fault is not 43 * handled by mmiotrace: 44 */ 45 static nokprobe_inline int 46 kmmio_fault(struct pt_regs *regs, unsigned long addr) 47 { 48 if (unlikely(is_kmmio_active())) 49 if (kmmio_handler(regs, addr) == 1) 50 return -1; 51 return 0; 52 } 53 54 /* 55 * Prefetch quirks: 56 * 57 * 32-bit mode: 58 * 59 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. 60 * Check that here and ignore it. This is AMD erratum #91. 61 * 62 * 64-bit mode: 63 * 64 * Sometimes the CPU reports invalid exceptions on prefetch. 65 * Check that here and ignore it. 66 * 67 * Opcode checker based on code by Richard Brunner. 68 */ 69 static inline int 70 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, 71 unsigned char opcode, int *prefetch) 72 { 73 unsigned char instr_hi = opcode & 0xf0; 74 unsigned char instr_lo = opcode & 0x0f; 75 76 switch (instr_hi) { 77 case 0x20: 78 case 0x30: 79 /* 80 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. 81 * In X86_64 long mode, the CPU will signal invalid 82 * opcode if some of these prefixes are present so 83 * X86_64 will never get here anyway 84 */ 85 return ((instr_lo & 7) == 0x6); 86 #ifdef CONFIG_X86_64 87 case 0x40: 88 /* 89 * In 64-bit mode 0x40..0x4F are valid REX prefixes 90 */ 91 return (!user_mode(regs) || user_64bit_mode(regs)); 92 #endif 93 case 0x60: 94 /* 0x64 thru 0x67 are valid prefixes in all modes. */ 95 return (instr_lo & 0xC) == 0x4; 96 case 0xF0: 97 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */ 98 return !instr_lo || (instr_lo>>1) == 1; 99 case 0x00: 100 /* Prefetch instruction is 0x0F0D or 0x0F18 */ 101 if (get_kernel_nofault(opcode, instr)) 102 return 0; 103 104 *prefetch = (instr_lo == 0xF) && 105 (opcode == 0x0D || opcode == 0x18); 106 return 0; 107 default: 108 return 0; 109 } 110 } 111 112 static bool is_amd_k8_pre_npt(void) 113 { 114 struct cpuinfo_x86 *c = &boot_cpu_data; 115 116 return unlikely(IS_ENABLED(CONFIG_CPU_SUP_AMD) && 117 c->x86_vendor == X86_VENDOR_AMD && 118 c->x86 == 0xf && c->x86_model < 0x40); 119 } 120 121 static int 122 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) 123 { 124 unsigned char *max_instr; 125 unsigned char *instr; 126 int prefetch = 0; 127 128 /* Erratum #91 affects AMD K8, pre-NPT CPUs */ 129 if (!is_amd_k8_pre_npt()) 130 return 0; 131 132 /* 133 * If it was a exec (instruction fetch) fault on NX page, then 134 * do not ignore the fault: 135 */ 136 if (error_code & X86_PF_INSTR) 137 return 0; 138 139 instr = (void *)convert_ip_to_linear(current, regs); 140 max_instr = instr + 15; 141 142 /* 143 * This code has historically always bailed out if IP points to a 144 * not-present page (e.g. due to a race). No one has ever 145 * complained about this. 146 */ 147 pagefault_disable(); 148 149 while (instr < max_instr) { 150 unsigned char opcode; 151 152 if (user_mode(regs)) { 153 if (get_user(opcode, (unsigned char __user *) instr)) 154 break; 155 } else { 156 if (get_kernel_nofault(opcode, instr)) 157 break; 158 } 159 160 instr++; 161 162 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch)) 163 break; 164 } 165 166 pagefault_enable(); 167 return prefetch; 168 } 169 170 DEFINE_SPINLOCK(pgd_lock); 171 LIST_HEAD(pgd_list); 172 173 #ifdef CONFIG_X86_32 174 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) 175 { 176 unsigned index = pgd_index(address); 177 pgd_t *pgd_k; 178 p4d_t *p4d, *p4d_k; 179 pud_t *pud, *pud_k; 180 pmd_t *pmd, *pmd_k; 181 182 pgd += index; 183 pgd_k = init_mm.pgd + index; 184 185 if (!pgd_present(*pgd_k)) 186 return NULL; 187 188 /* 189 * set_pgd(pgd, *pgd_k); here would be useless on PAE 190 * and redundant with the set_pmd() on non-PAE. As would 191 * set_p4d/set_pud. 192 */ 193 p4d = p4d_offset(pgd, address); 194 p4d_k = p4d_offset(pgd_k, address); 195 if (!p4d_present(*p4d_k)) 196 return NULL; 197 198 pud = pud_offset(p4d, address); 199 pud_k = pud_offset(p4d_k, address); 200 if (!pud_present(*pud_k)) 201 return NULL; 202 203 pmd = pmd_offset(pud, address); 204 pmd_k = pmd_offset(pud_k, address); 205 206 if (pmd_present(*pmd) != pmd_present(*pmd_k)) 207 set_pmd(pmd, *pmd_k); 208 209 if (!pmd_present(*pmd_k)) 210 return NULL; 211 else 212 BUG_ON(pmd_pfn(*pmd) != pmd_pfn(*pmd_k)); 213 214 return pmd_k; 215 } 216 217 /* 218 * Handle a fault on the vmalloc or module mapping area 219 * 220 * This is needed because there is a race condition between the time 221 * when the vmalloc mapping code updates the PMD to the point in time 222 * where it synchronizes this update with the other page-tables in the 223 * system. 224 * 225 * In this race window another thread/CPU can map an area on the same 226 * PMD, finds it already present and does not synchronize it with the 227 * rest of the system yet. As a result v[mz]alloc might return areas 228 * which are not mapped in every page-table in the system, causing an 229 * unhandled page-fault when they are accessed. 230 */ 231 static noinline int vmalloc_fault(unsigned long address) 232 { 233 unsigned long pgd_paddr; 234 pmd_t *pmd_k; 235 pte_t *pte_k; 236 237 /* Make sure we are in vmalloc area: */ 238 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 239 return -1; 240 241 /* 242 * Synchronize this task's top level page-table 243 * with the 'reference' page table. 244 * 245 * Do _not_ use "current" here. We might be inside 246 * an interrupt in the middle of a task switch.. 247 */ 248 pgd_paddr = read_cr3_pa(); 249 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); 250 if (!pmd_k) 251 return -1; 252 253 if (pmd_large(*pmd_k)) 254 return 0; 255 256 pte_k = pte_offset_kernel(pmd_k, address); 257 if (!pte_present(*pte_k)) 258 return -1; 259 260 return 0; 261 } 262 NOKPROBE_SYMBOL(vmalloc_fault); 263 264 void arch_sync_kernel_mappings(unsigned long start, unsigned long end) 265 { 266 unsigned long addr; 267 268 for (addr = start & PMD_MASK; 269 addr >= TASK_SIZE_MAX && addr < VMALLOC_END; 270 addr += PMD_SIZE) { 271 struct page *page; 272 273 spin_lock(&pgd_lock); 274 list_for_each_entry(page, &pgd_list, lru) { 275 spinlock_t *pgt_lock; 276 277 /* the pgt_lock only for Xen */ 278 pgt_lock = &pgd_page_get_mm(page)->page_table_lock; 279 280 spin_lock(pgt_lock); 281 vmalloc_sync_one(page_address(page), addr); 282 spin_unlock(pgt_lock); 283 } 284 spin_unlock(&pgd_lock); 285 } 286 } 287 288 static bool low_pfn(unsigned long pfn) 289 { 290 return pfn < max_low_pfn; 291 } 292 293 static void dump_pagetable(unsigned long address) 294 { 295 pgd_t *base = __va(read_cr3_pa()); 296 pgd_t *pgd = &base[pgd_index(address)]; 297 p4d_t *p4d; 298 pud_t *pud; 299 pmd_t *pmd; 300 pte_t *pte; 301 302 #ifdef CONFIG_X86_PAE 303 pr_info("*pdpt = %016Lx ", pgd_val(*pgd)); 304 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd)) 305 goto out; 306 #define pr_pde pr_cont 307 #else 308 #define pr_pde pr_info 309 #endif 310 p4d = p4d_offset(pgd, address); 311 pud = pud_offset(p4d, address); 312 pmd = pmd_offset(pud, address); 313 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd)); 314 #undef pr_pde 315 316 /* 317 * We must not directly access the pte in the highpte 318 * case if the page table is located in highmem. 319 * And let's rather not kmap-atomic the pte, just in case 320 * it's allocated already: 321 */ 322 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd)) 323 goto out; 324 325 pte = pte_offset_kernel(pmd, address); 326 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte)); 327 out: 328 pr_cont("\n"); 329 } 330 331 #else /* CONFIG_X86_64: */ 332 333 #ifdef CONFIG_CPU_SUP_AMD 334 static const char errata93_warning[] = 335 KERN_ERR 336 "******* Your BIOS seems to not contain a fix for K8 errata #93\n" 337 "******* Working around it, but it may cause SEGVs or burn power.\n" 338 "******* Please consider a BIOS update.\n" 339 "******* Disabling USB legacy in the BIOS may also help.\n"; 340 #endif 341 342 static int bad_address(void *p) 343 { 344 unsigned long dummy; 345 346 return get_kernel_nofault(dummy, (unsigned long *)p); 347 } 348 349 static void dump_pagetable(unsigned long address) 350 { 351 pgd_t *base = __va(read_cr3_pa()); 352 pgd_t *pgd = base + pgd_index(address); 353 p4d_t *p4d; 354 pud_t *pud; 355 pmd_t *pmd; 356 pte_t *pte; 357 358 if (bad_address(pgd)) 359 goto bad; 360 361 pr_info("PGD %lx ", pgd_val(*pgd)); 362 363 if (!pgd_present(*pgd)) 364 goto out; 365 366 p4d = p4d_offset(pgd, address); 367 if (bad_address(p4d)) 368 goto bad; 369 370 pr_cont("P4D %lx ", p4d_val(*p4d)); 371 if (!p4d_present(*p4d) || p4d_large(*p4d)) 372 goto out; 373 374 pud = pud_offset(p4d, address); 375 if (bad_address(pud)) 376 goto bad; 377 378 pr_cont("PUD %lx ", pud_val(*pud)); 379 if (!pud_present(*pud) || pud_large(*pud)) 380 goto out; 381 382 pmd = pmd_offset(pud, address); 383 if (bad_address(pmd)) 384 goto bad; 385 386 pr_cont("PMD %lx ", pmd_val(*pmd)); 387 if (!pmd_present(*pmd) || pmd_large(*pmd)) 388 goto out; 389 390 pte = pte_offset_kernel(pmd, address); 391 if (bad_address(pte)) 392 goto bad; 393 394 pr_cont("PTE %lx", pte_val(*pte)); 395 out: 396 pr_cont("\n"); 397 return; 398 bad: 399 pr_info("BAD\n"); 400 } 401 402 #endif /* CONFIG_X86_64 */ 403 404 /* 405 * Workaround for K8 erratum #93 & buggy BIOS. 406 * 407 * BIOS SMM functions are required to use a specific workaround 408 * to avoid corruption of the 64bit RIP register on C stepping K8. 409 * 410 * A lot of BIOS that didn't get tested properly miss this. 411 * 412 * The OS sees this as a page fault with the upper 32bits of RIP cleared. 413 * Try to work around it here. 414 * 415 * Note we only handle faults in kernel here. 416 * Does nothing on 32-bit. 417 */ 418 static int is_errata93(struct pt_regs *regs, unsigned long address) 419 { 420 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD) 421 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD 422 || boot_cpu_data.x86 != 0xf) 423 return 0; 424 425 if (user_mode(regs)) 426 return 0; 427 428 if (address != regs->ip) 429 return 0; 430 431 if ((address >> 32) != 0) 432 return 0; 433 434 address |= 0xffffffffUL << 32; 435 if ((address >= (u64)_stext && address <= (u64)_etext) || 436 (address >= MODULES_VADDR && address <= MODULES_END)) { 437 printk_once(errata93_warning); 438 regs->ip = address; 439 return 1; 440 } 441 #endif 442 return 0; 443 } 444 445 /* 446 * Work around K8 erratum #100 K8 in compat mode occasionally jumps 447 * to illegal addresses >4GB. 448 * 449 * We catch this in the page fault handler because these addresses 450 * are not reachable. Just detect this case and return. Any code 451 * segment in LDT is compatibility mode. 452 */ 453 static int is_errata100(struct pt_regs *regs, unsigned long address) 454 { 455 #ifdef CONFIG_X86_64 456 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32)) 457 return 1; 458 #endif 459 return 0; 460 } 461 462 /* Pentium F0 0F C7 C8 bug workaround: */ 463 static int is_f00f_bug(struct pt_regs *regs, unsigned long error_code, 464 unsigned long address) 465 { 466 #ifdef CONFIG_X86_F00F_BUG 467 if (boot_cpu_has_bug(X86_BUG_F00F) && !(error_code & X86_PF_USER) && 468 idt_is_f00f_address(address)) { 469 handle_invalid_op(regs); 470 return 1; 471 } 472 #endif 473 return 0; 474 } 475 476 static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index) 477 { 478 u32 offset = (index >> 3) * sizeof(struct desc_struct); 479 unsigned long addr; 480 struct ldttss_desc desc; 481 482 if (index == 0) { 483 pr_alert("%s: NULL\n", name); 484 return; 485 } 486 487 if (offset + sizeof(struct ldttss_desc) >= gdt->size) { 488 pr_alert("%s: 0x%hx -- out of bounds\n", name, index); 489 return; 490 } 491 492 if (copy_from_kernel_nofault(&desc, (void *)(gdt->address + offset), 493 sizeof(struct ldttss_desc))) { 494 pr_alert("%s: 0x%hx -- GDT entry is not readable\n", 495 name, index); 496 return; 497 } 498 499 addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24); 500 #ifdef CONFIG_X86_64 501 addr |= ((u64)desc.base3 << 32); 502 #endif 503 pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n", 504 name, index, addr, (desc.limit0 | (desc.limit1 << 16))); 505 } 506 507 static void 508 show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address) 509 { 510 if (!oops_may_print()) 511 return; 512 513 if (error_code & X86_PF_INSTR) { 514 unsigned int level; 515 pgd_t *pgd; 516 pte_t *pte; 517 518 pgd = __va(read_cr3_pa()); 519 pgd += pgd_index(address); 520 521 pte = lookup_address_in_pgd(pgd, address, &level); 522 523 if (pte && pte_present(*pte) && !pte_exec(*pte)) 524 pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n", 525 from_kuid(&init_user_ns, current_uid())); 526 if (pte && pte_present(*pte) && pte_exec(*pte) && 527 (pgd_flags(*pgd) & _PAGE_USER) && 528 (__read_cr4() & X86_CR4_SMEP)) 529 pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n", 530 from_kuid(&init_user_ns, current_uid())); 531 } 532 533 if (address < PAGE_SIZE && !user_mode(regs)) 534 pr_alert("BUG: kernel NULL pointer dereference, address: %px\n", 535 (void *)address); 536 else 537 pr_alert("BUG: unable to handle page fault for address: %px\n", 538 (void *)address); 539 540 pr_alert("#PF: %s %s in %s mode\n", 541 (error_code & X86_PF_USER) ? "user" : "supervisor", 542 (error_code & X86_PF_INSTR) ? "instruction fetch" : 543 (error_code & X86_PF_WRITE) ? "write access" : 544 "read access", 545 user_mode(regs) ? "user" : "kernel"); 546 pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code, 547 !(error_code & X86_PF_PROT) ? "not-present page" : 548 (error_code & X86_PF_RSVD) ? "reserved bit violation" : 549 (error_code & X86_PF_PK) ? "protection keys violation" : 550 "permissions violation"); 551 552 if (!(error_code & X86_PF_USER) && user_mode(regs)) { 553 struct desc_ptr idt, gdt; 554 u16 ldtr, tr; 555 556 /* 557 * This can happen for quite a few reasons. The more obvious 558 * ones are faults accessing the GDT, or LDT. Perhaps 559 * surprisingly, if the CPU tries to deliver a benign or 560 * contributory exception from user code and gets a page fault 561 * during delivery, the page fault can be delivered as though 562 * it originated directly from user code. This could happen 563 * due to wrong permissions on the IDT, GDT, LDT, TSS, or 564 * kernel or IST stack. 565 */ 566 store_idt(&idt); 567 568 /* Usable even on Xen PV -- it's just slow. */ 569 native_store_gdt(&gdt); 570 571 pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n", 572 idt.address, idt.size, gdt.address, gdt.size); 573 574 store_ldt(ldtr); 575 show_ldttss(&gdt, "LDTR", ldtr); 576 577 store_tr(tr); 578 show_ldttss(&gdt, "TR", tr); 579 } 580 581 dump_pagetable(address); 582 } 583 584 static noinline void 585 pgtable_bad(struct pt_regs *regs, unsigned long error_code, 586 unsigned long address) 587 { 588 struct task_struct *tsk; 589 unsigned long flags; 590 int sig; 591 592 flags = oops_begin(); 593 tsk = current; 594 sig = SIGKILL; 595 596 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", 597 tsk->comm, address); 598 dump_pagetable(address); 599 600 if (__die("Bad pagetable", regs, error_code)) 601 sig = 0; 602 603 oops_end(flags, regs, sig); 604 } 605 606 static void sanitize_error_code(unsigned long address, 607 unsigned long *error_code) 608 { 609 /* 610 * To avoid leaking information about the kernel page 611 * table layout, pretend that user-mode accesses to 612 * kernel addresses are always protection faults. 613 * 614 * NB: This means that failed vsyscalls with vsyscall=none 615 * will have the PROT bit. This doesn't leak any 616 * information and does not appear to cause any problems. 617 */ 618 if (address >= TASK_SIZE_MAX) 619 *error_code |= X86_PF_PROT; 620 } 621 622 static void set_signal_archinfo(unsigned long address, 623 unsigned long error_code) 624 { 625 struct task_struct *tsk = current; 626 627 tsk->thread.trap_nr = X86_TRAP_PF; 628 tsk->thread.error_code = error_code | X86_PF_USER; 629 tsk->thread.cr2 = address; 630 } 631 632 static noinline void 633 page_fault_oops(struct pt_regs *regs, unsigned long error_code, 634 unsigned long address) 635 { 636 #ifdef CONFIG_VMAP_STACK 637 struct stack_info info; 638 #endif 639 unsigned long flags; 640 int sig; 641 642 if (user_mode(regs)) { 643 /* 644 * Implicit kernel access from user mode? Skip the stack 645 * overflow and EFI special cases. 646 */ 647 goto oops; 648 } 649 650 #ifdef CONFIG_VMAP_STACK 651 /* 652 * Stack overflow? During boot, we can fault near the initial 653 * stack in the direct map, but that's not an overflow -- check 654 * that we're in vmalloc space to avoid this. 655 */ 656 if (is_vmalloc_addr((void *)address) && 657 get_stack_guard_info((void *)address, &info)) { 658 /* 659 * We're likely to be running with very little stack space 660 * left. It's plausible that we'd hit this condition but 661 * double-fault even before we get this far, in which case 662 * we're fine: the double-fault handler will deal with it. 663 * 664 * We don't want to make it all the way into the oops code 665 * and then double-fault, though, because we're likely to 666 * break the console driver and lose most of the stack dump. 667 */ 668 call_on_stack(__this_cpu_ist_top_va(DF) - sizeof(void*), 669 handle_stack_overflow, 670 ASM_CALL_ARG3, 671 , [arg1] "r" (regs), [arg2] "r" (address), [arg3] "r" (&info)); 672 673 unreachable(); 674 } 675 #endif 676 677 /* 678 * Buggy firmware could access regions which might page fault. If 679 * this happens, EFI has a special OOPS path that will try to 680 * avoid hanging the system. 681 */ 682 if (IS_ENABLED(CONFIG_EFI)) 683 efi_crash_gracefully_on_page_fault(address); 684 685 /* Only not-present faults should be handled by KFENCE. */ 686 if (!(error_code & X86_PF_PROT) && 687 kfence_handle_page_fault(address, error_code & X86_PF_WRITE, regs)) 688 return; 689 690 oops: 691 /* 692 * Oops. The kernel tried to access some bad page. We'll have to 693 * terminate things with extreme prejudice: 694 */ 695 flags = oops_begin(); 696 697 show_fault_oops(regs, error_code, address); 698 699 if (task_stack_end_corrupted(current)) 700 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); 701 702 sig = SIGKILL; 703 if (__die("Oops", regs, error_code)) 704 sig = 0; 705 706 /* Executive summary in case the body of the oops scrolled away */ 707 printk(KERN_DEFAULT "CR2: %016lx\n", address); 708 709 oops_end(flags, regs, sig); 710 } 711 712 static noinline void 713 kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code, 714 unsigned long address, int signal, int si_code, 715 u32 pkey) 716 { 717 WARN_ON_ONCE(user_mode(regs)); 718 719 /* Are we prepared to handle this kernel fault? */ 720 if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) { 721 /* 722 * Any interrupt that takes a fault gets the fixup. This makes 723 * the below recursive fault logic only apply to a faults from 724 * task context. 725 */ 726 if (in_interrupt()) 727 return; 728 729 /* 730 * Per the above we're !in_interrupt(), aka. task context. 731 * 732 * In this case we need to make sure we're not recursively 733 * faulting through the emulate_vsyscall() logic. 734 */ 735 if (current->thread.sig_on_uaccess_err && signal) { 736 sanitize_error_code(address, &error_code); 737 738 set_signal_archinfo(address, error_code); 739 740 if (si_code == SEGV_PKUERR) { 741 force_sig_pkuerr((void __user *)address, pkey); 742 } else { 743 /* XXX: hwpoison faults will set the wrong code. */ 744 force_sig_fault(signal, si_code, (void __user *)address); 745 } 746 } 747 748 /* 749 * Barring that, we can do the fixup and be happy. 750 */ 751 return; 752 } 753 754 /* 755 * AMD erratum #91 manifests as a spurious page fault on a PREFETCH 756 * instruction. 757 */ 758 if (is_prefetch(regs, error_code, address)) 759 return; 760 761 page_fault_oops(regs, error_code, address); 762 } 763 764 /* 765 * Print out info about fatal segfaults, if the show_unhandled_signals 766 * sysctl is set: 767 */ 768 static inline void 769 show_signal_msg(struct pt_regs *regs, unsigned long error_code, 770 unsigned long address, struct task_struct *tsk) 771 { 772 const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG; 773 /* This is a racy snapshot, but it's better than nothing. */ 774 int cpu = raw_smp_processor_id(); 775 776 if (!unhandled_signal(tsk, SIGSEGV)) 777 return; 778 779 if (!printk_ratelimit()) 780 return; 781 782 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx", 783 loglvl, tsk->comm, task_pid_nr(tsk), address, 784 (void *)regs->ip, (void *)regs->sp, error_code); 785 786 print_vma_addr(KERN_CONT " in ", regs->ip); 787 788 /* 789 * Dump the likely CPU where the fatal segfault happened. 790 * This can help identify faulty hardware. 791 */ 792 printk(KERN_CONT " likely on CPU %d (core %d, socket %d)", cpu, 793 topology_core_id(cpu), topology_physical_package_id(cpu)); 794 795 796 printk(KERN_CONT "\n"); 797 798 show_opcodes(regs, loglvl); 799 } 800 801 /* 802 * The (legacy) vsyscall page is the long page in the kernel portion 803 * of the address space that has user-accessible permissions. 804 */ 805 static bool is_vsyscall_vaddr(unsigned long vaddr) 806 { 807 return unlikely((vaddr & PAGE_MASK) == VSYSCALL_ADDR); 808 } 809 810 static void 811 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 812 unsigned long address, u32 pkey, int si_code) 813 { 814 struct task_struct *tsk = current; 815 816 if (!user_mode(regs)) { 817 kernelmode_fixup_or_oops(regs, error_code, address, 818 SIGSEGV, si_code, pkey); 819 return; 820 } 821 822 if (!(error_code & X86_PF_USER)) { 823 /* Implicit user access to kernel memory -- just oops */ 824 page_fault_oops(regs, error_code, address); 825 return; 826 } 827 828 /* 829 * User mode accesses just cause a SIGSEGV. 830 * It's possible to have interrupts off here: 831 */ 832 local_irq_enable(); 833 834 /* 835 * Valid to do another page fault here because this one came 836 * from user space: 837 */ 838 if (is_prefetch(regs, error_code, address)) 839 return; 840 841 if (is_errata100(regs, address)) 842 return; 843 844 sanitize_error_code(address, &error_code); 845 846 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address)) 847 return; 848 849 if (likely(show_unhandled_signals)) 850 show_signal_msg(regs, error_code, address, tsk); 851 852 set_signal_archinfo(address, error_code); 853 854 if (si_code == SEGV_PKUERR) 855 force_sig_pkuerr((void __user *)address, pkey); 856 else 857 force_sig_fault(SIGSEGV, si_code, (void __user *)address); 858 859 local_irq_disable(); 860 } 861 862 static noinline void 863 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 864 unsigned long address) 865 { 866 __bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR); 867 } 868 869 static void 870 __bad_area(struct pt_regs *regs, unsigned long error_code, 871 unsigned long address, u32 pkey, int si_code) 872 { 873 struct mm_struct *mm = current->mm; 874 /* 875 * Something tried to access memory that isn't in our memory map.. 876 * Fix it, but check if it's kernel or user first.. 877 */ 878 mmap_read_unlock(mm); 879 880 __bad_area_nosemaphore(regs, error_code, address, pkey, si_code); 881 } 882 883 static noinline void 884 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address) 885 { 886 __bad_area(regs, error_code, address, 0, SEGV_MAPERR); 887 } 888 889 static inline bool bad_area_access_from_pkeys(unsigned long error_code, 890 struct vm_area_struct *vma) 891 { 892 /* This code is always called on the current mm */ 893 bool foreign = false; 894 895 if (!cpu_feature_enabled(X86_FEATURE_OSPKE)) 896 return false; 897 if (error_code & X86_PF_PK) 898 return true; 899 /* this checks permission keys on the VMA: */ 900 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE), 901 (error_code & X86_PF_INSTR), foreign)) 902 return true; 903 return false; 904 } 905 906 static noinline void 907 bad_area_access_error(struct pt_regs *regs, unsigned long error_code, 908 unsigned long address, struct vm_area_struct *vma) 909 { 910 /* 911 * This OSPKE check is not strictly necessary at runtime. 912 * But, doing it this way allows compiler optimizations 913 * if pkeys are compiled out. 914 */ 915 if (bad_area_access_from_pkeys(error_code, vma)) { 916 /* 917 * A protection key fault means that the PKRU value did not allow 918 * access to some PTE. Userspace can figure out what PKRU was 919 * from the XSAVE state. This function captures the pkey from 920 * the vma and passes it to userspace so userspace can discover 921 * which protection key was set on the PTE. 922 * 923 * If we get here, we know that the hardware signaled a X86_PF_PK 924 * fault and that there was a VMA once we got in the fault 925 * handler. It does *not* guarantee that the VMA we find here 926 * was the one that we faulted on. 927 * 928 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4); 929 * 2. T1 : set PKRU to deny access to pkey=4, touches page 930 * 3. T1 : faults... 931 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5); 932 * 5. T1 : enters fault handler, takes mmap_lock, etc... 933 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really 934 * faulted on a pte with its pkey=4. 935 */ 936 u32 pkey = vma_pkey(vma); 937 938 __bad_area(regs, error_code, address, pkey, SEGV_PKUERR); 939 } else { 940 __bad_area(regs, error_code, address, 0, SEGV_ACCERR); 941 } 942 } 943 944 static void 945 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, 946 vm_fault_t fault) 947 { 948 /* Kernel mode? Handle exceptions or die: */ 949 if (!user_mode(regs)) { 950 kernelmode_fixup_or_oops(regs, error_code, address, 951 SIGBUS, BUS_ADRERR, ARCH_DEFAULT_PKEY); 952 return; 953 } 954 955 /* User-space => ok to do another page fault: */ 956 if (is_prefetch(regs, error_code, address)) 957 return; 958 959 sanitize_error_code(address, &error_code); 960 961 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address)) 962 return; 963 964 set_signal_archinfo(address, error_code); 965 966 #ifdef CONFIG_MEMORY_FAILURE 967 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { 968 struct task_struct *tsk = current; 969 unsigned lsb = 0; 970 971 pr_err( 972 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", 973 tsk->comm, tsk->pid, address); 974 if (fault & VM_FAULT_HWPOISON_LARGE) 975 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 976 if (fault & VM_FAULT_HWPOISON) 977 lsb = PAGE_SHIFT; 978 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb); 979 return; 980 } 981 #endif 982 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address); 983 } 984 985 static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte) 986 { 987 if ((error_code & X86_PF_WRITE) && !pte_write(*pte)) 988 return 0; 989 990 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte)) 991 return 0; 992 993 return 1; 994 } 995 996 /* 997 * Handle a spurious fault caused by a stale TLB entry. 998 * 999 * This allows us to lazily refresh the TLB when increasing the 1000 * permissions of a kernel page (RO -> RW or NX -> X). Doing it 1001 * eagerly is very expensive since that implies doing a full 1002 * cross-processor TLB flush, even if no stale TLB entries exist 1003 * on other processors. 1004 * 1005 * Spurious faults may only occur if the TLB contains an entry with 1006 * fewer permission than the page table entry. Non-present (P = 0) 1007 * and reserved bit (R = 1) faults are never spurious. 1008 * 1009 * There are no security implications to leaving a stale TLB when 1010 * increasing the permissions on a page. 1011 * 1012 * Returns non-zero if a spurious fault was handled, zero otherwise. 1013 * 1014 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3 1015 * (Optional Invalidation). 1016 */ 1017 static noinline int 1018 spurious_kernel_fault(unsigned long error_code, unsigned long address) 1019 { 1020 pgd_t *pgd; 1021 p4d_t *p4d; 1022 pud_t *pud; 1023 pmd_t *pmd; 1024 pte_t *pte; 1025 int ret; 1026 1027 /* 1028 * Only writes to RO or instruction fetches from NX may cause 1029 * spurious faults. 1030 * 1031 * These could be from user or supervisor accesses but the TLB 1032 * is only lazily flushed after a kernel mapping protection 1033 * change, so user accesses are not expected to cause spurious 1034 * faults. 1035 */ 1036 if (error_code != (X86_PF_WRITE | X86_PF_PROT) && 1037 error_code != (X86_PF_INSTR | X86_PF_PROT)) 1038 return 0; 1039 1040 pgd = init_mm.pgd + pgd_index(address); 1041 if (!pgd_present(*pgd)) 1042 return 0; 1043 1044 p4d = p4d_offset(pgd, address); 1045 if (!p4d_present(*p4d)) 1046 return 0; 1047 1048 if (p4d_large(*p4d)) 1049 return spurious_kernel_fault_check(error_code, (pte_t *) p4d); 1050 1051 pud = pud_offset(p4d, address); 1052 if (!pud_present(*pud)) 1053 return 0; 1054 1055 if (pud_large(*pud)) 1056 return spurious_kernel_fault_check(error_code, (pte_t *) pud); 1057 1058 pmd = pmd_offset(pud, address); 1059 if (!pmd_present(*pmd)) 1060 return 0; 1061 1062 if (pmd_large(*pmd)) 1063 return spurious_kernel_fault_check(error_code, (pte_t *) pmd); 1064 1065 pte = pte_offset_kernel(pmd, address); 1066 if (!pte_present(*pte)) 1067 return 0; 1068 1069 ret = spurious_kernel_fault_check(error_code, pte); 1070 if (!ret) 1071 return 0; 1072 1073 /* 1074 * Make sure we have permissions in PMD. 1075 * If not, then there's a bug in the page tables: 1076 */ 1077 ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd); 1078 WARN_ONCE(!ret, "PMD has incorrect permission bits\n"); 1079 1080 return ret; 1081 } 1082 NOKPROBE_SYMBOL(spurious_kernel_fault); 1083 1084 int show_unhandled_signals = 1; 1085 1086 static inline int 1087 access_error(unsigned long error_code, struct vm_area_struct *vma) 1088 { 1089 /* This is only called for the current mm, so: */ 1090 bool foreign = false; 1091 1092 /* 1093 * Read or write was blocked by protection keys. This is 1094 * always an unconditional error and can never result in 1095 * a follow-up action to resolve the fault, like a COW. 1096 */ 1097 if (error_code & X86_PF_PK) 1098 return 1; 1099 1100 /* 1101 * SGX hardware blocked the access. This usually happens 1102 * when the enclave memory contents have been destroyed, like 1103 * after a suspend/resume cycle. In any case, the kernel can't 1104 * fix the cause of the fault. Handle the fault as an access 1105 * error even in cases where no actual access violation 1106 * occurred. This allows userspace to rebuild the enclave in 1107 * response to the signal. 1108 */ 1109 if (unlikely(error_code & X86_PF_SGX)) 1110 return 1; 1111 1112 /* 1113 * Make sure to check the VMA so that we do not perform 1114 * faults just to hit a X86_PF_PK as soon as we fill in a 1115 * page. 1116 */ 1117 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE), 1118 (error_code & X86_PF_INSTR), foreign)) 1119 return 1; 1120 1121 if (error_code & X86_PF_WRITE) { 1122 /* write, present and write, not present: */ 1123 if (unlikely(!(vma->vm_flags & VM_WRITE))) 1124 return 1; 1125 return 0; 1126 } 1127 1128 /* read, present: */ 1129 if (unlikely(error_code & X86_PF_PROT)) 1130 return 1; 1131 1132 /* read, not present: */ 1133 if (unlikely(!vma_is_accessible(vma))) 1134 return 1; 1135 1136 return 0; 1137 } 1138 1139 bool fault_in_kernel_space(unsigned long address) 1140 { 1141 /* 1142 * On 64-bit systems, the vsyscall page is at an address above 1143 * TASK_SIZE_MAX, but is not considered part of the kernel 1144 * address space. 1145 */ 1146 if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address)) 1147 return false; 1148 1149 return address >= TASK_SIZE_MAX; 1150 } 1151 1152 /* 1153 * Called for all faults where 'address' is part of the kernel address 1154 * space. Might get called for faults that originate from *code* that 1155 * ran in userspace or the kernel. 1156 */ 1157 static void 1158 do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code, 1159 unsigned long address) 1160 { 1161 /* 1162 * Protection keys exceptions only happen on user pages. We 1163 * have no user pages in the kernel portion of the address 1164 * space, so do not expect them here. 1165 */ 1166 WARN_ON_ONCE(hw_error_code & X86_PF_PK); 1167 1168 #ifdef CONFIG_X86_32 1169 /* 1170 * We can fault-in kernel-space virtual memory on-demand. The 1171 * 'reference' page table is init_mm.pgd. 1172 * 1173 * NOTE! We MUST NOT take any locks for this case. We may 1174 * be in an interrupt or a critical region, and should 1175 * only copy the information from the master page table, 1176 * nothing more. 1177 * 1178 * Before doing this on-demand faulting, ensure that the 1179 * fault is not any of the following: 1180 * 1. A fault on a PTE with a reserved bit set. 1181 * 2. A fault caused by a user-mode access. (Do not demand- 1182 * fault kernel memory due to user-mode accesses). 1183 * 3. A fault caused by a page-level protection violation. 1184 * (A demand fault would be on a non-present page which 1185 * would have X86_PF_PROT==0). 1186 * 1187 * This is only needed to close a race condition on x86-32 in 1188 * the vmalloc mapping/unmapping code. See the comment above 1189 * vmalloc_fault() for details. On x86-64 the race does not 1190 * exist as the vmalloc mappings don't need to be synchronized 1191 * there. 1192 */ 1193 if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) { 1194 if (vmalloc_fault(address) >= 0) 1195 return; 1196 } 1197 #endif 1198 1199 if (is_f00f_bug(regs, hw_error_code, address)) 1200 return; 1201 1202 /* Was the fault spurious, caused by lazy TLB invalidation? */ 1203 if (spurious_kernel_fault(hw_error_code, address)) 1204 return; 1205 1206 /* kprobes don't want to hook the spurious faults: */ 1207 if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF))) 1208 return; 1209 1210 /* 1211 * Note, despite being a "bad area", there are quite a few 1212 * acceptable reasons to get here, such as erratum fixups 1213 * and handling kernel code that can fault, like get_user(). 1214 * 1215 * Don't take the mm semaphore here. If we fixup a prefetch 1216 * fault we could otherwise deadlock: 1217 */ 1218 bad_area_nosemaphore(regs, hw_error_code, address); 1219 } 1220 NOKPROBE_SYMBOL(do_kern_addr_fault); 1221 1222 /* 1223 * Handle faults in the user portion of the address space. Nothing in here 1224 * should check X86_PF_USER without a specific justification: for almost 1225 * all purposes, we should treat a normal kernel access to user memory 1226 * (e.g. get_user(), put_user(), etc.) the same as the WRUSS instruction. 1227 * The one exception is AC flag handling, which is, per the x86 1228 * architecture, special for WRUSS. 1229 */ 1230 static inline 1231 void do_user_addr_fault(struct pt_regs *regs, 1232 unsigned long error_code, 1233 unsigned long address) 1234 { 1235 struct vm_area_struct *vma; 1236 struct task_struct *tsk; 1237 struct mm_struct *mm; 1238 vm_fault_t fault; 1239 unsigned int flags = FAULT_FLAG_DEFAULT; 1240 1241 tsk = current; 1242 mm = tsk->mm; 1243 1244 if (unlikely((error_code & (X86_PF_USER | X86_PF_INSTR)) == X86_PF_INSTR)) { 1245 /* 1246 * Whoops, this is kernel mode code trying to execute from 1247 * user memory. Unless this is AMD erratum #93, which 1248 * corrupts RIP such that it looks like a user address, 1249 * this is unrecoverable. Don't even try to look up the 1250 * VMA or look for extable entries. 1251 */ 1252 if (is_errata93(regs, address)) 1253 return; 1254 1255 page_fault_oops(regs, error_code, address); 1256 return; 1257 } 1258 1259 /* kprobes don't want to hook the spurious faults: */ 1260 if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF))) 1261 return; 1262 1263 /* 1264 * Reserved bits are never expected to be set on 1265 * entries in the user portion of the page tables. 1266 */ 1267 if (unlikely(error_code & X86_PF_RSVD)) 1268 pgtable_bad(regs, error_code, address); 1269 1270 /* 1271 * If SMAP is on, check for invalid kernel (supervisor) access to user 1272 * pages in the user address space. The odd case here is WRUSS, 1273 * which, according to the preliminary documentation, does not respect 1274 * SMAP and will have the USER bit set so, in all cases, SMAP 1275 * enforcement appears to be consistent with the USER bit. 1276 */ 1277 if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) && 1278 !(error_code & X86_PF_USER) && 1279 !(regs->flags & X86_EFLAGS_AC))) { 1280 /* 1281 * No extable entry here. This was a kernel access to an 1282 * invalid pointer. get_kernel_nofault() will not get here. 1283 */ 1284 page_fault_oops(regs, error_code, address); 1285 return; 1286 } 1287 1288 /* 1289 * If we're in an interrupt, have no user context or are running 1290 * in a region with pagefaults disabled then we must not take the fault 1291 */ 1292 if (unlikely(faulthandler_disabled() || !mm)) { 1293 bad_area_nosemaphore(regs, error_code, address); 1294 return; 1295 } 1296 1297 /* 1298 * It's safe to allow irq's after cr2 has been saved and the 1299 * vmalloc fault has been handled. 1300 * 1301 * User-mode registers count as a user access even for any 1302 * potential system fault or CPU buglet: 1303 */ 1304 if (user_mode(regs)) { 1305 local_irq_enable(); 1306 flags |= FAULT_FLAG_USER; 1307 } else { 1308 if (regs->flags & X86_EFLAGS_IF) 1309 local_irq_enable(); 1310 } 1311 1312 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 1313 1314 if (error_code & X86_PF_WRITE) 1315 flags |= FAULT_FLAG_WRITE; 1316 if (error_code & X86_PF_INSTR) 1317 flags |= FAULT_FLAG_INSTRUCTION; 1318 1319 #ifdef CONFIG_X86_64 1320 /* 1321 * Faults in the vsyscall page might need emulation. The 1322 * vsyscall page is at a high address (>PAGE_OFFSET), but is 1323 * considered to be part of the user address space. 1324 * 1325 * The vsyscall page does not have a "real" VMA, so do this 1326 * emulation before we go searching for VMAs. 1327 * 1328 * PKRU never rejects instruction fetches, so we don't need 1329 * to consider the PF_PK bit. 1330 */ 1331 if (is_vsyscall_vaddr(address)) { 1332 if (emulate_vsyscall(error_code, regs, address)) 1333 return; 1334 } 1335 #endif 1336 1337 #ifdef CONFIG_PER_VMA_LOCK 1338 if (!(flags & FAULT_FLAG_USER)) 1339 goto lock_mmap; 1340 1341 vma = lock_vma_under_rcu(mm, address); 1342 if (!vma) 1343 goto lock_mmap; 1344 1345 if (unlikely(access_error(error_code, vma))) { 1346 vma_end_read(vma); 1347 goto lock_mmap; 1348 } 1349 fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs); 1350 vma_end_read(vma); 1351 1352 if (!(fault & VM_FAULT_RETRY)) { 1353 count_vm_vma_lock_event(VMA_LOCK_SUCCESS); 1354 goto done; 1355 } 1356 count_vm_vma_lock_event(VMA_LOCK_RETRY); 1357 1358 /* Quick path to respond to signals */ 1359 if (fault_signal_pending(fault, regs)) { 1360 if (!user_mode(regs)) 1361 kernelmode_fixup_or_oops(regs, error_code, address, 1362 SIGBUS, BUS_ADRERR, 1363 ARCH_DEFAULT_PKEY); 1364 return; 1365 } 1366 lock_mmap: 1367 #endif /* CONFIG_PER_VMA_LOCK */ 1368 1369 /* 1370 * Kernel-mode access to the user address space should only occur 1371 * on well-defined single instructions listed in the exception 1372 * tables. But, an erroneous kernel fault occurring outside one of 1373 * those areas which also holds mmap_lock might deadlock attempting 1374 * to validate the fault against the address space. 1375 * 1376 * Only do the expensive exception table search when we might be at 1377 * risk of a deadlock. This happens if we 1378 * 1. Failed to acquire mmap_lock, and 1379 * 2. The access did not originate in userspace. 1380 */ 1381 if (unlikely(!mmap_read_trylock(mm))) { 1382 if (!user_mode(regs) && !search_exception_tables(regs->ip)) { 1383 /* 1384 * Fault from code in kernel from 1385 * which we do not expect faults. 1386 */ 1387 bad_area_nosemaphore(regs, error_code, address); 1388 return; 1389 } 1390 retry: 1391 mmap_read_lock(mm); 1392 } else { 1393 /* 1394 * The above down_read_trylock() might have succeeded in 1395 * which case we'll have missed the might_sleep() from 1396 * down_read(): 1397 */ 1398 might_sleep(); 1399 } 1400 1401 vma = find_vma(mm, address); 1402 if (unlikely(!vma)) { 1403 bad_area(regs, error_code, address); 1404 return; 1405 } 1406 if (likely(vma->vm_start <= address)) 1407 goto good_area; 1408 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { 1409 bad_area(regs, error_code, address); 1410 return; 1411 } 1412 if (unlikely(expand_stack(vma, address))) { 1413 bad_area(regs, error_code, address); 1414 return; 1415 } 1416 1417 /* 1418 * Ok, we have a good vm_area for this memory access, so 1419 * we can handle it.. 1420 */ 1421 good_area: 1422 if (unlikely(access_error(error_code, vma))) { 1423 bad_area_access_error(regs, error_code, address, vma); 1424 return; 1425 } 1426 1427 /* 1428 * If for any reason at all we couldn't handle the fault, 1429 * make sure we exit gracefully rather than endlessly redo 1430 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if 1431 * we get VM_FAULT_RETRY back, the mmap_lock has been unlocked. 1432 * 1433 * Note that handle_userfault() may also release and reacquire mmap_lock 1434 * (and not return with VM_FAULT_RETRY), when returning to userland to 1435 * repeat the page fault later with a VM_FAULT_NOPAGE retval 1436 * (potentially after handling any pending signal during the return to 1437 * userland). The return to userland is identified whenever 1438 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags. 1439 */ 1440 fault = handle_mm_fault(vma, address, flags, regs); 1441 1442 if (fault_signal_pending(fault, regs)) { 1443 /* 1444 * Quick path to respond to signals. The core mm code 1445 * has unlocked the mm for us if we get here. 1446 */ 1447 if (!user_mode(regs)) 1448 kernelmode_fixup_or_oops(regs, error_code, address, 1449 SIGBUS, BUS_ADRERR, 1450 ARCH_DEFAULT_PKEY); 1451 return; 1452 } 1453 1454 /* The fault is fully completed (including releasing mmap lock) */ 1455 if (fault & VM_FAULT_COMPLETED) 1456 return; 1457 1458 /* 1459 * If we need to retry the mmap_lock has already been released, 1460 * and if there is a fatal signal pending there is no guarantee 1461 * that we made any progress. Handle this case first. 1462 */ 1463 if (unlikely(fault & VM_FAULT_RETRY)) { 1464 flags |= FAULT_FLAG_TRIED; 1465 goto retry; 1466 } 1467 1468 mmap_read_unlock(mm); 1469 #ifdef CONFIG_PER_VMA_LOCK 1470 done: 1471 #endif 1472 if (likely(!(fault & VM_FAULT_ERROR))) 1473 return; 1474 1475 if (fatal_signal_pending(current) && !user_mode(regs)) { 1476 kernelmode_fixup_or_oops(regs, error_code, address, 1477 0, 0, ARCH_DEFAULT_PKEY); 1478 return; 1479 } 1480 1481 if (fault & VM_FAULT_OOM) { 1482 /* Kernel mode? Handle exceptions or die: */ 1483 if (!user_mode(regs)) { 1484 kernelmode_fixup_or_oops(regs, error_code, address, 1485 SIGSEGV, SEGV_MAPERR, 1486 ARCH_DEFAULT_PKEY); 1487 return; 1488 } 1489 1490 /* 1491 * We ran out of memory, call the OOM killer, and return the 1492 * userspace (which will retry the fault, or kill us if we got 1493 * oom-killed): 1494 */ 1495 pagefault_out_of_memory(); 1496 } else { 1497 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| 1498 VM_FAULT_HWPOISON_LARGE)) 1499 do_sigbus(regs, error_code, address, fault); 1500 else if (fault & VM_FAULT_SIGSEGV) 1501 bad_area_nosemaphore(regs, error_code, address); 1502 else 1503 BUG(); 1504 } 1505 } 1506 NOKPROBE_SYMBOL(do_user_addr_fault); 1507 1508 static __always_inline void 1509 trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code, 1510 unsigned long address) 1511 { 1512 if (!trace_pagefault_enabled()) 1513 return; 1514 1515 if (user_mode(regs)) 1516 trace_page_fault_user(address, regs, error_code); 1517 else 1518 trace_page_fault_kernel(address, regs, error_code); 1519 } 1520 1521 static __always_inline void 1522 handle_page_fault(struct pt_regs *regs, unsigned long error_code, 1523 unsigned long address) 1524 { 1525 trace_page_fault_entries(regs, error_code, address); 1526 1527 if (unlikely(kmmio_fault(regs, address))) 1528 return; 1529 1530 /* Was the fault on kernel-controlled part of the address space? */ 1531 if (unlikely(fault_in_kernel_space(address))) { 1532 do_kern_addr_fault(regs, error_code, address); 1533 } else { 1534 do_user_addr_fault(regs, error_code, address); 1535 /* 1536 * User address page fault handling might have reenabled 1537 * interrupts. Fixing up all potential exit points of 1538 * do_user_addr_fault() and its leaf functions is just not 1539 * doable w/o creating an unholy mess or turning the code 1540 * upside down. 1541 */ 1542 local_irq_disable(); 1543 } 1544 } 1545 1546 DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault) 1547 { 1548 unsigned long address = read_cr2(); 1549 irqentry_state_t state; 1550 1551 prefetchw(¤t->mm->mmap_lock); 1552 1553 /* 1554 * KVM uses #PF vector to deliver 'page not present' events to guests 1555 * (asynchronous page fault mechanism). The event happens when a 1556 * userspace task is trying to access some valid (from guest's point of 1557 * view) memory which is not currently mapped by the host (e.g. the 1558 * memory is swapped out). Note, the corresponding "page ready" event 1559 * which is injected when the memory becomes available, is delivered via 1560 * an interrupt mechanism and not a #PF exception 1561 * (see arch/x86/kernel/kvm.c: sysvec_kvm_asyncpf_interrupt()). 1562 * 1563 * We are relying on the interrupted context being sane (valid RSP, 1564 * relevant locks not held, etc.), which is fine as long as the 1565 * interrupted context had IF=1. We are also relying on the KVM 1566 * async pf type field and CR2 being read consistently instead of 1567 * getting values from real and async page faults mixed up. 1568 * 1569 * Fingers crossed. 1570 * 1571 * The async #PF handling code takes care of idtentry handling 1572 * itself. 1573 */ 1574 if (kvm_handle_async_pf(regs, (u32)address)) 1575 return; 1576 1577 /* 1578 * Entry handling for valid #PF from kernel mode is slightly 1579 * different: RCU is already watching and ct_irq_enter() must not 1580 * be invoked because a kernel fault on a user space address might 1581 * sleep. 1582 * 1583 * In case the fault hit a RCU idle region the conditional entry 1584 * code reenabled RCU to avoid subsequent wreckage which helps 1585 * debuggability. 1586 */ 1587 state = irqentry_enter(regs); 1588 1589 instrumentation_begin(); 1590 handle_page_fault(regs, error_code, address); 1591 instrumentation_end(); 1592 1593 irqentry_exit(regs, state); 1594 } 1595