From: Marco Elver elver@google.com
Instead of removing the fault handling portion of the stack trace based on the fault handler's name, just use struct pt_regs directly.
Change kfence_handle_page_fault() to take a struct pt_regs, and plumb it through to kfence_report_error() for out-of-bounds, use-after-free, or invalid access errors, where pt_regs is used to generate the stack trace.
If the kernel is a DEBUG_KERNEL, also show registers for more information.
Link: https://lkml.kernel.org/r/20201105092133.2075331-1-elver@google.com Signed-off-by: Marco Elver elver@google.com Suggested-by: Mark Rutland mark.rutland@arm.com Acked-by: Mark Rutland mark.rutland@arm.com Cc: Alexander Potapenko glider@google.com Cc: Dmitry Vyukov dvyukov@google.com Cc: Jann Horn jannh@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Yingjie Shang 1415317271@qq.com Reviewed-by: Bixuan Cui cuibixuan@huawei.com --- arch/arm64/include/asm/kfence.h | 2 -- arch/arm64/mm/fault.c | 2 +- arch/x86/include/asm/kfence.h | 6 ---- arch/x86/mm/fault.c | 2 +- include/linux/kfence.h | 5 +-- mm/kfence/core.c | 10 +++--- mm/kfence/kfence.h | 4 +-- mm/kfence/report.c | 63 +++++++++++++++++++-------------- 8 files changed, 48 insertions(+), 46 deletions(-)
diff --git a/arch/arm64/include/asm/kfence.h b/arch/arm64/include/asm/kfence.h index 42a06f83850a..d061176d57ea 100644 --- a/arch/arm64/include/asm/kfence.h +++ b/arch/arm64/include/asm/kfence.h @@ -10,8 +10,6 @@
#include <asm/cacheflush.h>
-#define KFENCE_SKIP_ARCH_FAULT_HANDLER "el1_sync" - static inline bool arch_kfence_init_pool(void) { return true; }
static inline bool kfence_protect_page(unsigned long addr, bool protect) diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index d1a8b523d28e..a5fe9f7b423b 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -323,7 +323,7 @@ static void __do_kernel_fault(unsigned long addr, unsigned int esr, } else if (addr < PAGE_SIZE) { msg = "NULL pointer dereference"; } else { - if (kfence_handle_page_fault(addr)) + if (kfence_handle_page_fault(addr, regs)) return;
msg = "paging request"; diff --git a/arch/x86/include/asm/kfence.h b/arch/x86/include/asm/kfence.h index a0659dbd93ea..97bbb4a9083a 100644 --- a/arch/x86/include/asm/kfence.h +++ b/arch/x86/include/asm/kfence.h @@ -16,12 +16,6 @@ #include <asm/set_memory.h> #include <asm/tlbflush.h>
-/* - * The page fault handler entry function, up to which the stack trace is - * truncated in reports. - */ -#define KFENCE_SKIP_ARCH_FAULT_HANDLER "asm_exc_page_fault" - /* Force 4K pages for __kfence_pool. */ static inline bool arch_kfence_init_pool(void) { diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 35901aa6ad1c..f5f359ccaeae 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -734,7 +734,7 @@ no_context(struct pt_regs *regs, unsigned long error_code, efi_recover_from_page_fault(address);
/* Only not-present faults should be handled by KFENCE. */ - if (!(error_code & X86_PF_PROT) && kfence_handle_page_fault(address)) + if (!(error_code & X86_PF_PROT) && kfence_handle_page_fault(address, regs)) return; oops: /* diff --git a/include/linux/kfence.h b/include/linux/kfence.h index 81f3911cb298..5a56bcf5606c 100644 --- a/include/linux/kfence.h +++ b/include/linux/kfence.h @@ -186,6 +186,7 @@ static __always_inline __must_check bool kfence_free(void *addr) /** * kfence_handle_page_fault() - perform page fault handling for KFENCE pages * @addr: faulting address + * @regs: current struct pt_regs (can be NULL, but shows full stack trace) * * Return: * * false - address outside KFENCE pool, @@ -196,7 +197,7 @@ static __always_inline __must_check bool kfence_free(void *addr) * cases KFENCE prints an error message and marks the offending page as * present, so that the kernel can proceed. */ -bool __must_check kfence_handle_page_fault(unsigned long addr); +bool __must_check kfence_handle_page_fault(unsigned long addr, struct pt_regs *regs);
#else /* CONFIG_KFENCE */
@@ -209,7 +210,7 @@ static inline size_t kfence_ksize(const void *addr) { return 0; } static inline void *kfence_object_start(const void *addr) { return NULL; } static inline void __kfence_free(void *addr) { } static inline bool __must_check kfence_free(void *addr) { return false; } -static inline bool __must_check kfence_handle_page_fault(unsigned long addr) { return false; } +static inline bool __must_check kfence_handle_page_fault(unsigned long addr, struct pt_regs *regs) { return false; }
#endif
diff --git a/mm/kfence/core.c b/mm/kfence/core.c index d6a32c13336b..61c76670a7a9 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -216,7 +216,7 @@ static inline bool check_canary_byte(u8 *addr) return true;
atomic_long_inc(&counters[KFENCE_COUNTER_BUGS]); - kfence_report_error((unsigned long)addr, addr_to_metadata((unsigned long)addr), + kfence_report_error((unsigned long)addr, NULL, addr_to_metadata((unsigned long)addr), KFENCE_ERROR_CORRUPTION); return false; } @@ -351,7 +351,7 @@ static void kfence_guarded_free(void *addr, struct kfence_metadata *meta, bool z if (meta->state != KFENCE_OBJECT_ALLOCATED || meta->addr != (unsigned long)addr) { /* Invalid or double-free, bail out. */ atomic_long_inc(&counters[KFENCE_COUNTER_BUGS]); - kfence_report_error((unsigned long)addr, meta, KFENCE_ERROR_INVALID_FREE); + kfence_report_error((unsigned long)addr, NULL, meta, KFENCE_ERROR_INVALID_FREE); raw_spin_unlock_irqrestore(&meta->lock, flags); return; } @@ -766,7 +766,7 @@ void __kfence_free(void *addr) kfence_guarded_free(addr, meta, false); }
-bool kfence_handle_page_fault(unsigned long addr) +bool kfence_handle_page_fault(unsigned long addr, struct pt_regs *regs) { const int page_index = (addr - (unsigned long)__kfence_pool) / PAGE_SIZE; struct kfence_metadata *to_report = NULL; @@ -829,11 +829,11 @@ bool kfence_handle_page_fault(unsigned long addr)
out: if (to_report) { - kfence_report_error(addr, to_report, error_type); + kfence_report_error(addr, regs, to_report, error_type); raw_spin_unlock_irqrestore(&to_report->lock, flags); } else { /* This may be a UAF or OOB access, but we can't be sure. */ - kfence_report_error(addr, NULL, KFENCE_ERROR_INVALID); + kfence_report_error(addr, regs, NULL, KFENCE_ERROR_INVALID); }
return kfence_unprotect(addr); /* Unprotect and let access proceed. */ diff --git a/mm/kfence/kfence.h b/mm/kfence/kfence.h index 1014060f9707..0d83e628a97d 100644 --- a/mm/kfence/kfence.h +++ b/mm/kfence/kfence.h @@ -105,8 +105,8 @@ enum kfence_error_type { KFENCE_ERROR_INVALID_FREE, /* Invalid free. */ };
-void kfence_report_error(unsigned long address, const struct kfence_metadata *meta, - enum kfence_error_type type); +void kfence_report_error(unsigned long address, struct pt_regs *regs, + const struct kfence_metadata *meta, enum kfence_error_type type);
void kfence_print_object(struct seq_file *seq, const struct kfence_metadata *meta);
diff --git a/mm/kfence/report.c b/mm/kfence/report.c index 64f27c8d46a3..4dbfa9a382e4 100644 --- a/mm/kfence/report.c +++ b/mm/kfence/report.c @@ -10,6 +10,7 @@ #include <linux/kernel.h> #include <linux/lockdep.h> #include <linux/printk.h> +#include <linux/sched/debug.h> #include <linux/seq_file.h> #include <linux/stacktrace.h> #include <linux/string.h> @@ -41,7 +42,6 @@ static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries { char buf[64]; int skipnr, fallback = 0; - bool is_access_fault = false;
if (type) { /* Depending on error type, find different stack entries. */ @@ -49,8 +49,12 @@ static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries case KFENCE_ERROR_UAF: case KFENCE_ERROR_OOB: case KFENCE_ERROR_INVALID: - is_access_fault = true; - break; + /* + * kfence_handle_page_fault() may be called with pt_regs + * set to NULL; in that case we'll simply show the full + * stack trace. + */ + return 0; case KFENCE_ERROR_CORRUPTION: case KFENCE_ERROR_INVALID_FREE: break; @@ -60,26 +64,21 @@ static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries for (skipnr = 0; skipnr < num_entries; skipnr++) { int len = scnprintf(buf, sizeof(buf), "%ps", (void *)stack_entries[skipnr]);
- if (is_access_fault) { - if (!strncmp(buf, KFENCE_SKIP_ARCH_FAULT_HANDLER, len)) - goto found; - } else { - if (str_has_prefix(buf, "kfence_") || str_has_prefix(buf, "__kfence_") || - !strncmp(buf, "__slab_free", len)) { - /* - * In case of tail calls from any of the below - * to any of the above. - */ - fallback = skipnr + 1; - } - - /* Also the *_bulk() variants by only checking prefixes. */ - if (str_has_prefix(buf, "kfree") || - str_has_prefix(buf, "kmem_cache_free") || - str_has_prefix(buf, "__kmalloc") || - str_has_prefix(buf, "kmem_cache_alloc")) - goto found; + if (str_has_prefix(buf, "kfence_") || str_has_prefix(buf, "__kfence_") || + !strncmp(buf, "__slab_free", len)) { + /* + * In case of tail calls from any of the below + * to any of the above. + */ + fallback = skipnr + 1; } + + /* Also the *_bulk() variants by only checking prefixes. */ + if (str_has_prefix(buf, "kfree") || + str_has_prefix(buf, "kmem_cache_free") || + str_has_prefix(buf, "__kmalloc") || + str_has_prefix(buf, "kmem_cache_alloc")) + goto found; } if (fallback < num_entries) return fallback; @@ -157,13 +156,20 @@ static void print_diff_canary(unsigned long address, size_t bytes_to_show, pr_cont(" ]"); }
-void kfence_report_error(unsigned long address, const struct kfence_metadata *meta, - enum kfence_error_type type) +void kfence_report_error(unsigned long address, struct pt_regs *regs, + const struct kfence_metadata *meta, enum kfence_error_type type) { unsigned long stack_entries[KFENCE_STACK_DEPTH] = { 0 }; - int num_stack_entries = stack_trace_save(stack_entries, KFENCE_STACK_DEPTH, 1); - int skipnr = get_stack_skipnr(stack_entries, num_stack_entries, &type); const ptrdiff_t object_index = meta ? meta - kfence_metadata : -1; + int num_stack_entries; + int skipnr = 0; + + if (regs) { + num_stack_entries = stack_trace_save_regs(regs, stack_entries, KFENCE_STACK_DEPTH, 0); + } else { + num_stack_entries = stack_trace_save(stack_entries, KFENCE_STACK_DEPTH, 1); + skipnr = get_stack_skipnr(stack_entries, num_stack_entries, &type); + }
/* Require non-NULL meta, except if KFENCE_ERROR_INVALID. */ if (WARN_ON(type != KFENCE_ERROR_INVALID && !meta)) @@ -227,7 +233,10 @@ void kfence_report_error(unsigned long address, const struct kfence_metadata *me
/* Print report footer. */ pr_err("\n"); - dump_stack_print_info(KERN_ERR); + if (IS_ENABLED(CONFIG_DEBUG_KERNEL) && regs) + show_regs(regs); + else + dump_stack_print_info(KERN_ERR); pr_err("==================================================================\n");
lockdep_on();
-
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