diff options
Diffstat (limited to 'arch/x86/mm/fault.c')
| -rw-r--r-- | arch/x86/mm/fault.c | 822 |
1 files changed, 430 insertions, 392 deletions
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 629fdf13f846..7b0d4ab894c8 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -9,6 +9,7 @@ #include <linux/kdebug.h> /* oops_begin/end, ... */ #include <linux/extable.h> /* search_exception_tables */ #include <linux/memblock.h> /* max_low_pfn */ +#include <linux/kfence.h> /* kfence_handle_page_fault */ #include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */ #include <linux/mmiotrace.h> /* kmmio_handler, ... */ #include <linux/perf_event.h> /* perf_sw_event */ @@ -16,20 +17,22 @@ #include <linux/prefetch.h> /* prefetchw */ #include <linux/context_tracking.h> /* exception_enter(), ... */ #include <linux/uaccess.h> /* faulthandler_disabled() */ -#include <linux/efi.h> /* efi_recover_from_page_fault()*/ +#include <linux/efi.h> /* efi_crash_gracefully_on_page_fault()*/ #include <linux/mm_types.h> #include <asm/cpufeature.h> /* boot_cpu_has, ... */ #include <asm/traps.h> /* dotraplinkage, ... */ -#include <asm/pgalloc.h> /* pgd_*(), ... */ #include <asm/fixmap.h> /* VSYSCALL_ADDR */ #include <asm/vsyscall.h> /* emulate_vsyscall */ #include <asm/vm86.h> /* struct vm86 */ #include <asm/mmu_context.h> /* vma_pkey() */ -#include <asm/efi.h> /* efi_recover_from_page_fault()*/ +#include <asm/efi.h> /* efi_crash_gracefully_on_page_fault()*/ #include <asm/desc.h> /* store_idt(), ... */ #include <asm/cpu_entry_area.h> /* exception stack */ #include <asm/pgtable_areas.h> /* VMALLOC_START, ... */ +#include <asm/kvm_para.h> /* kvm_handle_async_pf */ +#include <asm/vdso.h> /* fixup_vdso_exception() */ +#include <asm/irq_stack.h> #define CREATE_TRACE_POINTS #include <asm/trace/exceptions.h> @@ -53,7 +56,7 @@ kmmio_fault(struct pt_regs *regs, unsigned long addr) * 32-bit mode: * * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. - * Check that here and ignore it. + * Check that here and ignore it. This is AMD erratum #91. * * 64-bit mode: * @@ -82,11 +85,7 @@ check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, #ifdef CONFIG_X86_64 case 0x40: /* - * In AMD64 long mode 0x40..0x4F are valid REX prefixes - * Need to figure out under what instruction mode the - * instruction was issued. Could check the LDT for lm, - * but for now it's good enough to assume that long - * mode only uses well known segments or kernel. + * In 64-bit mode 0x40..0x4F are valid REX prefixes */ return (!user_mode(regs) || user_64bit_mode(regs)); #endif @@ -98,7 +97,7 @@ check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, return !instr_lo || (instr_lo>>1) == 1; case 0x00: /* Prefetch instruction is 0x0F0D or 0x0F18 */ - if (probe_kernel_address(instr, opcode)) + if (get_kernel_nofault(opcode, instr)) return 0; *prefetch = (instr_lo == 0xF) && @@ -109,6 +108,15 @@ check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, } } +static bool is_amd_k8_pre_npt(void) +{ + struct cpuinfo_x86 *c = &boot_cpu_data; + + return unlikely(IS_ENABLED(CONFIG_CPU_SUP_AMD) && + c->x86_vendor == X86_VENDOR_AMD && + c->x86 == 0xf && c->x86_model < 0x40); +} + static int is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) { @@ -116,6 +124,10 @@ is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) unsigned char *instr; int prefetch = 0; + /* Erratum #91 affects AMD K8, pre-NPT CPUs */ + if (!is_amd_k8_pre_npt()) + return 0; + /* * If it was a exec (instruction fetch) fault on NX page, then * do not ignore the fault: @@ -126,20 +138,31 @@ is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) instr = (void *)convert_ip_to_linear(current, regs); max_instr = instr + 15; - if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX) - return 0; + /* + * This code has historically always bailed out if IP points to a + * not-present page (e.g. due to a race). No one has ever + * complained about this. + */ + pagefault_disable(); while (instr < max_instr) { unsigned char opcode; - if (probe_kernel_address(instr, opcode)) - break; + if (user_mode(regs)) { + if (get_user(opcode, (unsigned char __user *) instr)) + break; + } else { + if (get_kernel_nofault(opcode, instr)) + break; + } instr++; if (!check_prefetch_opcode(regs, instr, opcode, &prefetch)) break; } + + pagefault_enable(); return prefetch; } @@ -190,47 +213,19 @@ static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) return pmd_k; } -static void vmalloc_sync(void) -{ - unsigned long address; - - if (SHARED_KERNEL_PMD) - return; - - for (address = VMALLOC_START & PMD_MASK; - address >= TASK_SIZE_MAX && address < VMALLOC_END; - address += PMD_SIZE) { - struct page *page; - - spin_lock(&pgd_lock); - list_for_each_entry(page, &pgd_list, lru) { - spinlock_t *pgt_lock; - - /* the pgt_lock only for Xen */ - pgt_lock = &pgd_page_get_mm(page)->page_table_lock; - - spin_lock(pgt_lock); - vmalloc_sync_one(page_address(page), address); - spin_unlock(pgt_lock); - } - spin_unlock(&pgd_lock); - } -} - -void vmalloc_sync_mappings(void) -{ - vmalloc_sync(); -} - -void vmalloc_sync_unmappings(void) -{ - vmalloc_sync(); -} - /* - * 32-bit: - * * Handle a fault on the vmalloc or module mapping area + * + * This is needed because there is a race condition between the time + * when the vmalloc mapping code updates the PMD to the point in time + * where it synchronizes this update with the other page-tables in the + * system. + * + * In this race window another thread/CPU can map an area on the same + * PMD, finds it already present and does not synchronize it with the + * rest of the system yet. As a result v[mz]alloc might return areas + * which are not mapped in every page-table in the system, causing an + * unhandled page-fault when they are accessed. */ static noinline int vmalloc_fault(unsigned long address) { @@ -265,22 +260,48 @@ static noinline int vmalloc_fault(unsigned long address) } NOKPROBE_SYMBOL(vmalloc_fault); -/* - * Did it hit the DOS screen memory VA from vm86 mode? - */ -static inline void -check_v8086_mode(struct pt_regs *regs, unsigned long address, - struct task_struct *tsk) +static void __arch_sync_kernel_mappings(unsigned long start, unsigned long end) { -#ifdef CONFIG_VM86 - unsigned long bit; + unsigned long addr; - if (!v8086_mode(regs) || !tsk->thread.vm86) - return; + for (addr = start & PMD_MASK; + addr >= TASK_SIZE_MAX && addr < VMALLOC_END; + addr += PMD_SIZE) { + struct page *page; + + spin_lock(&pgd_lock); + list_for_each_entry(page, &pgd_list, lru) { + spinlock_t *pgt_lock; + + /* the pgt_lock only for Xen */ + pgt_lock = &pgd_page_get_mm(page)->page_table_lock; + + spin_lock(pgt_lock); + vmalloc_sync_one(page_address(page), addr); + spin_unlock(pgt_lock); + } + spin_unlock(&pgd_lock); + } +} - bit = (address - 0xA0000) >> PAGE_SHIFT; - if (bit < 32) - tsk->thread.vm86->screen_bitmap |= 1 << bit; +void arch_sync_kernel_mappings(unsigned long start, unsigned long end) +{ + __arch_sync_kernel_mappings(start, end); +#ifdef CONFIG_KMSAN + /* + * KMSAN maintains two additional metadata page mappings for the + * [VMALLOC_START, VMALLOC_END) range. These mappings start at + * KMSAN_VMALLOC_SHADOW_START and KMSAN_VMALLOC_ORIGIN_START and + * have to be synced together with the vmalloc memory mapping. + */ + if (start >= VMALLOC_START && end < VMALLOC_END) { + __arch_sync_kernel_mappings( + start - VMALLOC_START + KMSAN_VMALLOC_SHADOW_START, + end - VMALLOC_START + KMSAN_VMALLOC_SHADOW_START); + __arch_sync_kernel_mappings( + start - VMALLOC_START + KMSAN_VMALLOC_ORIGIN_START, + end - VMALLOC_START + KMSAN_VMALLOC_ORIGIN_START); + } #endif } @@ -329,96 +350,6 @@ out: #else /* CONFIG_X86_64: */ -void vmalloc_sync_mappings(void) -{ - /* - * 64-bit mappings might allocate new p4d/pud pages - * that need to be propagated to all tasks' PGDs. - */ - sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END); -} - -void vmalloc_sync_unmappings(void) -{ - /* - * Unmappings never allocate or free p4d/pud pages. - * No work is required here. - */ -} - -/* - * 64-bit: - * - * Handle a fault on the vmalloc area - */ -static noinline int vmalloc_fault(unsigned long address) -{ - pgd_t *pgd, *pgd_k; - p4d_t *p4d, *p4d_k; - pud_t *pud; - pmd_t *pmd; - pte_t *pte; - - /* Make sure we are in vmalloc area: */ - if (!(address >= VMALLOC_START && address < VMALLOC_END)) - return -1; - - /* - * Copy kernel mappings over when needed. This can also - * happen within a race in page table update. In the later - * case just flush: - */ - pgd = (pgd_t *)__va(read_cr3_pa()) + pgd_index(address); - pgd_k = pgd_offset_k(address); - if (pgd_none(*pgd_k)) - return -1; - - if (pgtable_l5_enabled()) { - if (pgd_none(*pgd)) { - set_pgd(pgd, *pgd_k); - arch_flush_lazy_mmu_mode(); - } else { - BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_k)); - } - } - - /* With 4-level paging, copying happens on the p4d level. */ - p4d = p4d_offset(pgd, address); - p4d_k = p4d_offset(pgd_k, address); - if (p4d_none(*p4d_k)) - return -1; - - if (p4d_none(*p4d) && !pgtable_l5_enabled()) { - set_p4d(p4d, *p4d_k); - arch_flush_lazy_mmu_mode(); - } else { - BUG_ON(p4d_pfn(*p4d) != p4d_pfn(*p4d_k)); - } - - BUILD_BUG_ON(CONFIG_PGTABLE_LEVELS < 4); - - pud = pud_offset(p4d, address); - if (pud_none(*pud)) - return -1; - - if (pud_large(*pud)) - return 0; - - pmd = pmd_offset(pud, address); - if (pmd_none(*pmd)) - return -1; - - if (pmd_large(*pmd)) - return 0; - - pte = pte_offset_kernel(pmd, address); - if (!pte_present(*pte)) - return -1; - - return 0; -} -NOKPROBE_SYMBOL(vmalloc_fault); - #ifdef CONFIG_CPU_SUP_AMD static const char errata93_warning[] = KERN_ERR @@ -428,20 +359,11 @@ KERN_ERR "******* Disabling USB legacy in the BIOS may also help.\n"; #endif -/* - * No vm86 mode in 64-bit mode: - */ -static inline void -check_v8086_mode(struct pt_regs *regs, unsigned long address, - struct task_struct *tsk) -{ -} - static int bad_address(void *p) { unsigned long dummy; - return probe_kernel_address((unsigned long *)p, dummy); + return get_kernel_nofault(dummy, (unsigned long *)p); } static void dump_pagetable(unsigned long address) @@ -520,6 +442,9 @@ static int is_errata93(struct pt_regs *regs, unsigned long address) || boot_cpu_data.x86 != 0xf) return 0; + if (user_mode(regs)) + return 0; + if (address != regs->ip) return 0; @@ -554,21 +479,15 @@ static int is_errata100(struct pt_regs *regs, unsigned long address) return 0; } -static int is_f00f_bug(struct pt_regs *regs, unsigned long address) +/* Pentium F0 0F C7 C8 bug workaround: */ +static int is_f00f_bug(struct pt_regs *regs, unsigned long error_code, + unsigned long address) { #ifdef CONFIG_X86_F00F_BUG - unsigned long nr; - - /* - * Pentium F0 0F C7 C8 bug workaround: - */ - if (boot_cpu_has_bug(X86_BUG_F00F)) { - nr = (address - idt_descr.address) >> 3; - - if (nr == 6) { - do_invalid_op(regs, 0); - return 1; - } + if (boot_cpu_has_bug(X86_BUG_F00F) && !(error_code & X86_PF_USER) && + idt_is_f00f_address(address)) { + handle_invalid_op(regs); + return 1; } #endif return 0; @@ -590,7 +509,7 @@ static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index) return; } - if (probe_kernel_read(&desc, (void *)(gdt->address + offset), + if (copy_from_kernel_nofault(&desc, (void *)(gdt->address + offset), sizeof(struct ldttss_desc))) { pr_alert("%s: 0x%hx -- GDT entry is not readable\n", name, index); @@ -704,11 +623,9 @@ pgtable_bad(struct pt_regs *regs, unsigned long error_code, oops_end(flags, regs, sig); } -static void set_signal_archinfo(unsigned long address, - unsigned long error_code) +static void sanitize_error_code(unsigned long address, + unsigned long *error_code) { - struct task_struct *tsk = current; - /* * To avoid leaking information about the kernel page * table layout, pretend that user-mode accesses to @@ -719,7 +636,13 @@ static void set_signal_archinfo(unsigned long address, * information and does not appear to cause any problems. */ if (address >= TASK_SIZE_MAX) - error_code |= X86_PF_PROT; + *error_code |= X86_PF_PROT; +} + +static void set_signal_archinfo(unsigned long address, + unsigned long error_code) +{ + struct task_struct *tsk = current; tsk->thread.trap_nr = X86_TRAP_PF; tsk->thread.error_code = error_code | X86_PF_USER; @@ -727,51 +650,23 @@ static void set_signal_archinfo(unsigned long address, } static noinline void -no_context(struct pt_regs *regs, unsigned long error_code, - unsigned long address, int signal, int si_code) +page_fault_oops(struct pt_regs *regs, unsigned long error_code, + unsigned long address) { - struct task_struct *tsk = current; +#ifdef CONFIG_VMAP_STACK + struct stack_info info; +#endif unsigned long flags; int sig; if (user_mode(regs)) { /* - * This is an implicit supervisor-mode access from user - * mode. Bypass all the kernel-mode recovery code and just - * OOPS. + * Implicit kernel access from user mode? Skip the stack + * overflow and EFI special cases. */ goto oops; } - /* Are we prepared to handle this kernel fault? */ - if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) { - /* - * Any interrupt that takes a fault gets the fixup. This makes - * the below recursive fault logic only apply to a faults from - * task context. - */ - if (in_interrupt()) - return; - - /* - * Per the above we're !in_interrupt(), aka. task context. - * - * In this case we need to make sure we're not recursively - * faulting through the emulate_vsyscall() logic. - */ - if (current->thread.sig_on_uaccess_err && signal) { - set_signal_archinfo(address, error_code); - - /* XXX: hwpoison faults will set the wrong code. */ - force_sig_fault(signal, si_code, (void __user *)address); - } - - /* - * Barring that, we can do the fixup and be happy. - */ - return; - } - #ifdef CONFIG_VMAP_STACK /* * Stack overflow? During boot, we can fault near the initial @@ -779,9 +674,7 @@ no_context(struct pt_regs *regs, unsigned long error_code, * that we're in vmalloc space to avoid this. */ if (is_vmalloc_addr((void *)address) && - (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) || - address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) { - unsigned long stack = __this_cpu_ist_top_va(DF) - sizeof(void *); + get_stack_guard_info((void *)address, &info)) { /* * We're likely to be running with very little stack space * left. It's plausible that we'd hit this condition but @@ -792,41 +685,28 @@ no_context(struct pt_regs *regs, unsigned long error_code, * and then double-fault, though, because we're likely to * break the console driver and lose most of the stack dump. */ - asm volatile ("movq %[stack], %%rsp\n\t" - "call handle_stack_overflow\n\t" - "1: jmp 1b" - : ASM_CALL_CONSTRAINT - : "D" ("kernel stack overflow (page fault)"), - "S" (regs), "d" (address), - [stack] "rm" (stack)); + call_on_stack(__this_cpu_ist_top_va(DF) - sizeof(void*), + handle_stack_overflow, + ASM_CALL_ARG3, + , [arg1] "r" (regs), [arg2] "r" (address), [arg3] "r" (&info)); + unreachable(); } #endif /* - * 32-bit: - * - * Valid to do another page fault here, because if this fault - * had been triggered by is_prefetch fixup_exception would have - * handled it. - * - * 64-bit: - * - * Hall of shame of CPU/BIOS bugs. + * Buggy firmware could access regions which might page fault. If + * this happens, EFI has a special OOPS path that will try to + * avoid hanging the system. */ - if (is_prefetch(regs, error_code, address)) - return; + if (IS_ENABLED(CONFIG_EFI)) + efi_crash_gracefully_on_page_fault(address); - if (is_errata93(regs, address)) + /* Only not-present faults should be handled by KFENCE. */ + if (!(error_code & X86_PF_PROT) && + kfence_handle_page_fault(address, error_code & X86_PF_WRITE, regs)) return; - /* - * Buggy firmware could access regions which might page fault, try to - * recover from such faults. - */ - if (IS_ENABLED(CONFIG_EFI)) - efi_recover_from_page_fault(address); - oops: /* * Oops. The kernel tried to access some bad page. We'll have to @@ -836,7 +716,7 @@ oops: show_fault_oops(regs, error_code, address); - if (task_stack_end_corrupted(tsk)) + if (task_stack_end_corrupted(current)) printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); sig = SIGKILL; @@ -849,6 +729,58 @@ oops: oops_end(flags, regs, sig); } +static noinline void +kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code, + unsigned long address, int signal, int si_code, + u32 pkey) +{ + WARN_ON_ONCE(user_mode(regs)); + + /* Are we prepared to handle this kernel fault? */ + if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) { + /* + * Any interrupt that takes a fault gets the fixup. This makes + * the below recursive fault logic only apply to a faults from + * task context. + */ + if (in_interrupt()) + return; + + /* + * Per the above we're !in_interrupt(), aka. task context. + * + * In this case we need to make sure we're not recursively + * faulting through the emulate_vsyscall() logic. + */ + if (current->thread.sig_on_uaccess_err && signal) { + sanitize_error_code(address, &error_code); + + set_signal_archinfo(address, error_code); + + if (si_code == SEGV_PKUERR) { + force_sig_pkuerr((void __user *)address, pkey); + } else { + /* XXX: hwpoison faults will set the wrong code. */ + force_sig_fault(signal, si_code, (void __user *)address); + } + } + + /* + * Barring that, we can do the fixup and be happy. + */ + return; + } + + /* + * AMD erratum #91 manifests as a spurious page fault on a PREFETCH + * instruction. + */ + if (is_prefetch(regs, error_code, address)) + return; + + page_fault_oops(regs, error_code, address); +} + /* * Print out info about fatal segfaults, if the show_unhandled_signals * sysctl is set: @@ -858,6 +790,8 @@ show_signal_msg(struct pt_regs *regs, unsigned long error_code, unsigned long address, struct task_struct *tsk) { const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG; + /* This is a racy snapshot, but it's better than nothing. */ + int cpu = raw_smp_processor_id(); if (!unhandled_signal(tsk, SIGSEGV)) return; @@ -871,6 +805,14 @@ show_signal_msg(struct pt_regs *regs, unsigned long error_code, print_vma_addr(KERN_CONT " in ", regs->ip); + /* + * Dump the likely CPU where the fatal segfault happened. + * This can help identify faulty hardware. + */ + printk(KERN_CONT " likely on CPU %d (core %d, socket %d)", cpu, + topology_core_id(cpu), topology_physical_package_id(cpu)); + + printk(KERN_CONT "\n"); show_opcodes(regs, loglvl); @@ -891,48 +833,50 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, { struct task_struct *tsk = current; - /* User mode accesses just cause a SIGSEGV */ - if (user_mode(regs) && (error_code & X86_PF_USER)) { - /* - * It's possible to have interrupts off here: - */ - local_irq_enable(); + if (!user_mode(regs)) { + kernelmode_fixup_or_oops(regs, error_code, address, + SIGSEGV, si_code, pkey); + return; + } - /* - * Valid to do another page fault here because this one came - * from user space: - */ - if (is_prefetch(regs, error_code, address)) - return; + if (!(error_code & X86_PF_USER)) { + /* Implicit user access to kernel memory -- just oops */ + page_fault_oops(regs, error_code, address); + return; + } - if (is_errata100(regs, address)) - return; + /* + * User mode accesses just cause a SIGSEGV. + * It's possible to have interrupts off here: + */ + local_irq_enable(); - /* - * To avoid leaking information about the kernel page table - * layout, pretend that user-mode accesses to kernel addresses - * are always protection faults. - */ - if (address >= TASK_SIZE_MAX) - error_code |= X86_PF_PROT; + /* + * Valid to do another page fault here because this one came + * from user space: + */ + if (is_prefetch(regs, error_code, address)) + return; - if (likely(show_unhandled_signals)) - show_signal_msg(regs, error_code, address, tsk); + if (is_errata100(regs, address)) + return; - set_signal_archinfo(address, error_code); + sanitize_error_code(address, &error_code); - if (si_code == SEGV_PKUERR) - force_sig_pkuerr((void __user *)address, pkey); + if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address)) + return; - force_sig_fault(SIGSEGV, si_code, (void __user *)address); + if (likely(show_unhandled_signals)) + show_signal_msg(regs, error_code, address, tsk); - return; - } + set_signal_archinfo(address, error_code); - if (is_f00f_bug(regs, address)) - return; + if (si_code == SEGV_PKUERR) + force_sig_pkuerr((void __user *)address, pkey); + else + force_sig_fault(SIGSEGV, si_code, (void __user *)address); - no_context(regs, error_code, address, SIGSEGV, si_code); + local_irq_disable(); } static noinline void @@ -951,7 +895,7 @@ __bad_area(struct pt_regs *regs, unsigned long error_code, * Something tried to access memory that isn't in our memory map.. * Fix it, but check if it's kernel or user first.. */ - up_read(&mm->mmap_sem); + mmap_read_unlock(mm); __bad_area_nosemaphore(regs, error_code, address, pkey, si_code); } @@ -968,7 +912,7 @@ static inline bool bad_area_access_from_pkeys(unsigned long error_code, /* This code is always called on the current mm */ bool foreign = false; - if (!boot_cpu_has(X86_FEATURE_OSPKE)) + if (!cpu_feature_enabled(X86_FEATURE_OSPKE)) return false; if (error_code & X86_PF_PK) return true; @@ -1005,7 +949,7 @@ bad_area_access_error(struct pt_regs *regs, unsigned long error_code, * 2. T1 : set PKRU to deny access to pkey=4, touches page * 3. T1 : faults... * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5); - * 5. T1 : enters fault handler, takes mmap_sem, etc... + * 5. T1 : enters fault handler, takes mmap_lock, etc... * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really * faulted on a pte with its pkey=4. */ @@ -1022,8 +966,9 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, vm_fault_t fault) { /* Kernel mode? Handle exceptions or die: */ - if (!(error_code & X86_PF_USER)) { - no_context(regs, error_code, address, SIGBUS, BUS_ADRERR); + if (!user_mode(regs)) { + kernelmode_fixup_or_oops(regs, error_code, address, + SIGBUS, BUS_ADRERR, ARCH_DEFAULT_PKEY); return; } @@ -1031,6 +976,11 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, if (is_prefetch(regs, error_code, address)) return; + sanitize_error_code(address, &error_code); + + if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address)) + return; + set_signal_archinfo(address, error_code); #ifdef CONFIG_MEMORY_FAILURE @@ -1052,40 +1002,6 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address); } -static noinline void -mm_fault_error(struct pt_regs *regs, unsigned long error_code, - unsigned long address, vm_fault_t fault) -{ - if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) { - no_context(regs, error_code, address, 0, 0); - return; - } - - if (fault & VM_FAULT_OOM) { - /* Kernel mode? Handle exceptions or die: */ - if (!(error_code & X86_PF_USER)) { - no_context(regs, error_code, address, - SIGSEGV, SEGV_MAPERR); - return; - } - - /* - * We ran out of memory, call the OOM killer, and return the - * userspace (which will retry the fault, or kill us if we got - * oom-killed): - */ - pagefault_out_of_memory(); - } else { - if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| - VM_FAULT_HWPOISON_LARGE)) - do_sigbus(regs, error_code, address, fault); - else if (fault & VM_FAULT_SIGSEGV) - bad_area_nosemaphore(regs, error_code, address); - else - BUG(); - } -} - static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte) { if ((error_code & X86_PF_WRITE) && !pte_write(*pte)) @@ -1202,6 +1118,18 @@ access_error(unsigned long error_code, struct vm_area_struct *vma) return 1; /* + * SGX hardware blocked the access. This usually happens + * when the enclave memory contents have been destroyed, like + * after a suspend/resume cycle. In any case, the kernel can't + * fix the cause of the fault. Handle the fault as an access + * error even in cases where no actual access violation + * occurred. This allows userspace to rebuild the enclave in + * response to the signal. + */ + if (unlikely(error_code & X86_PF_SGX)) + return 1; + + /* * Make sure to check the VMA so that we do not perform * faults just to hit a X86_PF_PK as soon as we fill in a * page. @@ -1222,13 +1150,13 @@ access_error(unsigned long error_code, struct vm_area_struct *vma) return 1; /* read, not present: */ - if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))) + if (unlikely(!vma_is_accessible(vma))) return 1; return 0; } -static int fault_in_kernel_space(unsigned long address) +bool fault_in_kernel_space(unsigned long address) { /* * On 64-bit systems, the vsyscall page is at an address above @@ -1257,6 +1185,7 @@ do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code, */ WARN_ON_ONCE(hw_error_code & X86_PF_PK); +#ifdef CONFIG_X86_32 /* * We can fault-in kernel-space virtual memory on-demand. The * 'reference' page table is init_mm.pgd. @@ -1274,18 +1203,28 @@ do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code, * 3. A fault caused by a page-level protection violation. * (A demand fault would be on a non-present page which * would have X86_PF_PROT==0). + * + * This is only needed to close a race condition on x86-32 in + * the vmalloc mapping/unmapping code. See the comment above + * vmalloc_fault() for details. On x86-64 the race does not + * exist as the vmalloc mappings don't need to be synchronized + * there. */ if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) { if (vmalloc_fault(address) >= 0) return; } +#endif + + if (is_f00f_bug(regs, hw_error_code, address)) + return; /* Was the fault spurious, caused by lazy TLB invalidation? */ if (spurious_kernel_fault(hw_error_code, address)) return; /* kprobes don't want to hook the spurious faults: */ - if (kprobe_page_fault(regs, X86_TRAP_PF)) + if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF))) return; /* @@ -1300,31 +1239,53 @@ do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code, } NOKPROBE_SYMBOL(do_kern_addr_fault); -/* Handle faults in the user portion of the address space */ +/* + * Handle faults in the user portion of the address space. Nothing in here + * should check X86_PF_USER without a specific justification: for almost + * all purposes, we should treat a normal kernel access to user memory + * (e.g. get_user(), put_user(), etc.) the same as the WRUSS instruction. + * The one exception is AC flag handling, which is, per the x86 + * architecture, special for WRUSS. + */ static inline void do_user_addr_fault(struct pt_regs *regs, - unsigned long hw_error_code, + unsigned long error_code, unsigned long address) { struct vm_area_struct *vma; struct task_struct *tsk; struct mm_struct *mm; - vm_fault_t fault, major = 0; - unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; + vm_fault_t fault; + unsigned int flags = FAULT_FLAG_DEFAULT; tsk = current; mm = tsk->mm; + if (unlikely((error_code & (X86_PF_USER | X86_PF_INSTR)) == X86_PF_INSTR)) { + /* + * Whoops, this is kernel mode code trying to execute from + * user memory. Unless this is AMD erratum #93, which + * corrupts RIP such that it looks like a user address, + * this is unrecoverable. Don't even try to look up the + * VMA or look for extable entries. + */ + if (is_errata93(regs, address)) + return; + + page_fault_oops(regs, error_code, address); + return; + } + /* kprobes don't want to hook the spurious faults: */ - if (unlikely(kprobe_page_fault(regs, X86_TRAP_PF))) + if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF))) return; /* * Reserved bits are never expected to be set on * entries in the user portion of the page tables. */ - if (unlikely(hw_error_code & X86_PF_RSVD)) - pgtable_bad(regs, hw_error_code, address); + if (unlikely(error_code & X86_PF_RSVD)) + pgtable_bad(regs, error_code, address); /* * If SMAP is on, check for invalid kernel (supervisor) access to user @@ -1334,10 +1295,13 @@ void do_user_addr_fault(struct pt_regs *regs, * enforcement appears to be consistent with the USER bit. */ if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) && - !(hw_error_code & X86_PF_USER) && - !(regs->flags & X86_EFLAGS_AC))) - { - bad_area_nosemaphore(regs, hw_error_code, address); + !(error_code & X86_PF_USER) && + !(regs->flags & X86_EFLAGS_AC))) { + /* + * No extable entry here. This was a kernel access to an + * invalid pointer. get_kernel_nofault() will not get here. + */ + page_fault_oops(regs, error_code, address); return; } @@ -1346,7 +1310,7 @@ void do_user_addr_fault(struct pt_regs *regs, * in a region with pagefaults disabled then we must not take the fault */ if (unlikely(faulthandler_disabled() || !mm)) { - bad_area_nosemaphore(regs, hw_error_code, address); + bad_area_nosemaphore(regs, error_code, address); return; } @@ -1367,9 +1331,9 @@ void do_user_addr_fault(struct pt_regs *regs, perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); - if (hw_error_code & X86_PF_WRITE) + if (error_code & X86_PF_WRITE) flags |= FAULT_FLAG_WRITE; - if (hw_error_code & X86_PF_INSTR) + if (error_code & X86_PF_INSTR) flags |= FAULT_FLAG_INSTRUCTION; #ifdef CONFIG_X86_64 @@ -1385,7 +1349,7 @@ void do_user_addr_fault(struct pt_regs *regs, * to consider the PF_PK bit. */ if (is_vsyscall_vaddr(address)) { - if (emulate_vsyscall(hw_error_code, regs, address)) + if (emulate_vsyscall(error_code, regs, address)) return; } #endif @@ -1394,25 +1358,25 @@ void do_user_addr_fault(struct pt_regs *regs, * Kernel-mode access to the user address space should only occur * on well-defined single instructions listed in the exception * tables. But, an erroneous kernel fault occurring outside one of - * those areas which also holds mmap_sem might deadlock attempting + * those areas which also holds mmap_lock might deadlock attempting * to validate the fault against the address space. * * Only do the expensive exception table search when we might be at * risk of a deadlock. This happens if we - * 1. Failed to acquire mmap_sem, and + * 1. Failed to acquire mmap_lock, and * 2. The access did not originate in userspace. */ - if (unlikely(!down_read_trylock(&mm->mmap_sem))) { + if (unlikely(!mmap_read_trylock(mm))) { if (!user_mode(regs) && !search_exception_tables(regs->ip)) { /* * Fault from code in kernel from * which we do not expect faults. */ - bad_area_nosemaphore(regs, hw_error_code, address); + bad_area_nosemaphore(regs, error_code, address); return; } retry: - down_read(&mm->mmap_sem); + mmap_read_lock(mm); } else { /* * The above down_read_trylock() might have succeeded in @@ -1424,17 +1388,17 @@ retry: vma = find_vma(mm, address); if (unlikely(!vma)) { - bad_area(regs, hw_error_code, address); + bad_area(regs, error_code, address); return; } if (likely(vma->vm_start <= address)) goto good_area; if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { - bad_area(regs, hw_error_code, address); + bad_area(regs, error_code, address); return; } if (unlikely(expand_stack(vma, address))) { - bad_area(regs, hw_error_code, address); + bad_area(regs, error_code, address); return; } @@ -1443,8 +1407,8 @@ retry: * we can handle it.. */ good_area: - if (unlikely(access_error(hw_error_code, vma))) { - bad_area_access_error(regs, hw_error_code, address, vma); + if (unlikely(access_error(error_code, vma))) { + bad_area_access_error(regs, error_code, address, vma); return; } @@ -1452,60 +1416,77 @@ good_area: * If for any reason at all we couldn't handle the fault, * make sure we exit gracefully rather than endlessly redo * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if - * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked. + * we get VM_FAULT_RETRY back, the mmap_lock has been unlocked. * - * Note that handle_userfault() may also release and reacquire mmap_sem + * Note that handle_userfault() may also release and reacquire mmap_lock * (and not return with VM_FAULT_RETRY), when returning to userland to * repeat the page fault later with a VM_FAULT_NOPAGE retval * (potentially after handling any pending signal during the return to * userland). The return to userland is identified whenever * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags. */ - fault = handle_mm_fault(vma, address, flags); - major |= fault & VM_FAULT_MAJOR; + fault = handle_mm_fault(vma, address, flags, regs); + + if (fault_signal_pending(fault, regs)) { + /* + * Quick path to respond to signals. The core mm code + * has unlocked the mm for us if we get here. + */ + if (!user_mode(regs)) + kernelmode_fixup_or_oops(regs, error_code, address, + SIGBUS, BUS_ADRERR, + ARCH_DEFAULT_PKEY); + return; + } + + /* The fault is fully completed (including releasing mmap lock) */ + if (fault & VM_FAULT_COMPLETED) + return; /* - * If we need to retry the mmap_sem has already been released, + * If we need to retry the mmap_lock has already been released, * and if there is a fatal signal pending there is no guarantee * that we made any progress. Handle this case first. */ if (unlikely(fault & VM_FAULT_RETRY)) { - /* Retry at most once */ - if (flags & FAULT_FLAG_ALLOW_RETRY) { - flags &= ~FAULT_FLAG_ALLOW_RETRY; - flags |= FAULT_FLAG_TRIED; - if (!fatal_signal_pending(tsk)) - goto retry; - } - - /* User mode? Just return to handle the fatal exception */ - if (flags & FAULT_FLAG_USER) - return; + flags |= FAULT_FLAG_TRIED; + goto retry; + } - /* Not returning to user mode? Handle exceptions or die: */ - no_context(regs, hw_error_code, address, SIGBUS, BUS_ADRERR); + mmap_read_unlock(mm); + if (likely(!(fault & VM_FAULT_ERROR))) return; - } - up_read(&mm->mmap_sem); - if (unlikely(fault & VM_FAULT_ERROR)) { - mm_fault_error(regs, hw_error_code, address, fault); + if (fatal_signal_pending(current) && !user_mode(regs)) { + kernelmode_fixup_or_oops(regs, error_code, address, + 0, 0, ARCH_DEFAULT_PKEY); return; } - /* - * Major/minor page fault accounting. If any of the events - * returned VM_FAULT_MAJOR, we account it as a major fault. - */ - if (major) { - tsk->maj_flt++; - perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); + if (fault & VM_FAULT_OOM) { + /* Kernel mode? Handle exceptions or die: */ + if (!user_mode(regs)) { + kernelmode_fixup_or_oops(regs, error_code, address, + SIGSEGV, SEGV_MAPERR, + ARCH_DEFAULT_PKEY); + return; + } + + /* + * We ran out of memory, call the OOM killer, and return the + * userspace (which will retry the fault, or kill us if we got + * oom-killed): + */ + pagefault_out_of_memory(); } else { - tsk->min_flt++; - perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); + if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| + VM_FAULT_HWPOISON_LARGE)) + do_sigbus(regs, error_code, address, fault); + else if (fault & VM_FAULT_SIGSEGV) + bad_area_nosemaphore(regs, error_code, address); + else + BUG(); } - - check_v8086_mode(regs, address, tsk); } NOKPROBE_SYMBOL(do_user_addr_fault); @@ -1522,20 +1503,77 @@ trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code, trace_page_fault_kernel(address, regs, error_code); } -dotraplinkage void -do_page_fault(struct pt_regs *regs, unsigned long hw_error_code, - unsigned long address) +static __always_inline void +handle_page_fault(struct pt_regs *regs, unsigned long error_code, + unsigned long address) { - prefetchw(¤t->mm->mmap_sem); - trace_page_fault_entries(regs, hw_error_code, address); + trace_page_fault_entries(regs, error_code, address); if (unlikely(kmmio_fault(regs, address))) return; /* Was the fault on kernel-controlled part of the address space? */ - if (unlikely(fault_in_kernel_space(address))) - do_kern_addr_fault(regs, hw_error_code, address); - else - do_user_addr_fault(regs, hw_error_code, address); + if (unlikely(fault_in_kernel_space(address))) { + do_kern_addr_fault(regs, error_code, address); + } else { + do_user_addr_fault(regs, error_code, address); + /* + * User address page fault handling might have reenabled + * interrupts. Fixing up all potential exit points of + * do_user_addr_fault() and its leaf functions is just not + * doable w/o creating an unholy mess or turning the code + * upside down. + */ + local_irq_disable(); + } +} + +DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault) +{ + unsigned long address = read_cr2(); + irqentry_state_t state; + + prefetchw(¤t->mm->mmap_lock); + + /* + * KVM uses #PF vector to deliver 'page not present' events to guests + * (asynchronous page fault mechanism). The event happens when a + * userspace task is trying to access some valid (from guest's point of + * view) memory which is not currently mapped by the host (e.g. the + * memory is swapped out). Note, the corresponding "page ready" event + * which is injected when the memory becomes available, is delivered via + * an interrupt mechanism and not a #PF exception + * (see arch/x86/kernel/kvm.c: sysvec_kvm_asyncpf_interrupt()). + * + * We are relying on the interrupted context being sane (valid RSP, + * relevant locks not held, etc.), which is fine as long as the + * interrupted context had IF=1. We are also relying on the KVM + * async pf type field and CR2 being read consistently instead of + * getting values from real and async page faults mixed up. + * + * Fingers crossed. + * + * The async #PF handling code takes care of idtentry handling + * itself. + */ + if (kvm_handle_async_pf(regs, (u32)address)) + return; + + /* + * Entry handling for valid #PF from kernel mode is slightly + * different: RCU is already watching and ct_irq_enter() must not + * be invoked because a kernel fault on a user space address might + * sleep. + * + * In case the fault hit a RCU idle region the conditional entry + * code reenabled RCU to avoid subsequent wreckage which helps + * debuggability. + */ + state = irqentry_enter(regs); + + instrumentation_begin(); + handle_page_fault(regs, error_code, address); + instrumentation_end(); + + irqentry_exit(regs, state); } -NOKPROBE_SYMBOL(do_page_fault); |