From 3de0de758029a0beb1d47facd3d390d2804a3e94 Mon Sep 17 00:00:00 2001 From: Kuan-Ying Lee Date: Wed, 15 Jun 2022 14:22:18 +0800 Subject: [PATCH] kasan: separate double free case from invalid free Currently, KASAN describes all invalid-free/double-free bugs as "double-free or invalid-free". This is ambiguous. KASAN should report "double-free" when a double-free is a more likely cause (the address points to the start of an object) and report "invalid-free" otherwise [1]. [1] https://bugzilla.kernel.org/show_bug.cgi?id=212193 Link: https://lkml.kernel.org/r/20220615062219.22618-1-Kuan-Ying.Lee@mediatek.com Signed-off-by: Kuan-Ying Lee Reviewed-by: Dmitry Vyukov Reviewed-by: Andrey Konovalov Cc: Andrey Ryabinin Cc: Alexander Potapenko Cc: Vincenzo Frascino Cc: Matthias Brugger Cc: Chinwen Chang Cc: Yee Lee Cc: Andrew Yang Signed-off-by: Andrew Morton --- mm/kasan/common.c | 8 ++++---- mm/kasan/kasan.h | 3 ++- mm/kasan/report.c | 12 ++++++++---- 3 files changed, 14 insertions(+), 9 deletions(-) diff --git a/mm/kasan/common.c b/mm/kasan/common.c index c40c0e7b3b5f..707c3a527fcb 100644 --- a/mm/kasan/common.c +++ b/mm/kasan/common.c @@ -343,7 +343,7 @@ static inline bool ____kasan_slab_free(struct kmem_cache *cache, void *object, if (unlikely(nearest_obj(cache, virt_to_slab(object), object) != object)) { - kasan_report_invalid_free(tagged_object, ip); + kasan_report_invalid_free(tagged_object, ip, KASAN_REPORT_INVALID_FREE); return true; } @@ -352,7 +352,7 @@ static inline bool ____kasan_slab_free(struct kmem_cache *cache, void *object, return false; if (!kasan_byte_accessible(tagged_object)) { - kasan_report_invalid_free(tagged_object, ip); + kasan_report_invalid_free(tagged_object, ip, KASAN_REPORT_DOUBLE_FREE); return true; } @@ -377,12 +377,12 @@ bool __kasan_slab_free(struct kmem_cache *cache, void *object, static inline bool ____kasan_kfree_large(void *ptr, unsigned long ip) { if (ptr != page_address(virt_to_head_page(ptr))) { - kasan_report_invalid_free(ptr, ip); + kasan_report_invalid_free(ptr, ip, KASAN_REPORT_INVALID_FREE); return true; } if (!kasan_byte_accessible(ptr)) { - kasan_report_invalid_free(ptr, ip); + kasan_report_invalid_free(ptr, ip, KASAN_REPORT_DOUBLE_FREE); return true; } diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index 610d60d6e5b8..01c03e45acd4 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -125,6 +125,7 @@ static inline bool kasan_sync_fault_possible(void) enum kasan_report_type { KASAN_REPORT_ACCESS, KASAN_REPORT_INVALID_FREE, + KASAN_REPORT_DOUBLE_FREE, }; struct kasan_report_info { @@ -277,7 +278,7 @@ static inline void kasan_print_address_stack_frame(const void *addr) { } bool kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip); -void kasan_report_invalid_free(void *object, unsigned long ip); +void kasan_report_invalid_free(void *object, unsigned long ip, enum kasan_report_type type); struct page *kasan_addr_to_page(const void *addr); struct slab *kasan_addr_to_slab(const void *addr); diff --git a/mm/kasan/report.c b/mm/kasan/report.c index b341a191651d..fe3f606b3a98 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c @@ -176,8 +176,12 @@ static void end_report(unsigned long *flags, void *addr) static void print_error_description(struct kasan_report_info *info) { if (info->type == KASAN_REPORT_INVALID_FREE) { - pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", - (void *)info->ip); + pr_err("BUG: KASAN: invalid-free in %pS\n", (void *)info->ip); + return; + } + + if (info->type == KASAN_REPORT_DOUBLE_FREE) { + pr_err("BUG: KASAN: double-free in %pS\n", (void *)info->ip); return; } @@ -433,7 +437,7 @@ static void print_report(struct kasan_report_info *info) } } -void kasan_report_invalid_free(void *ptr, unsigned long ip) +void kasan_report_invalid_free(void *ptr, unsigned long ip, enum kasan_report_type type) { unsigned long flags; struct kasan_report_info info; @@ -448,7 +452,7 @@ void kasan_report_invalid_free(void *ptr, unsigned long ip) start_report(&flags, true); - info.type = KASAN_REPORT_INVALID_FREE; + info.type = type; info.access_addr = ptr; info.first_bad_addr = kasan_reset_tag(ptr); info.access_size = 0;