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