From 5ab6d91ac998158d04f9563335aa5f1409eda971 Mon Sep 17 00:00:00 2001 From: Andrey Konovalov Date: Wed, 3 May 2017 14:56:47 -0700 Subject: [PATCH] kasan: improve double-free report format Changes double-free report header from BUG: Double free or freeing an invalid pointer Unexpected shadow byte: 0xFB to BUG: KASAN: double-free or invalid-free in kmalloc_oob_left+0xe5/0xef This makes a bug uniquely identifiable by the first report line. To account for removing of the unexpected shadow value, print shadow bytes at the end of the report as in reports for other kinds of bugs. Link: http://lkml.kernel.org/r/20170302134851.101218-9-andreyknvl@google.com Signed-off-by: Andrey Konovalov Acked-by: Dmitry Vyukov Cc: Andrey Ryabinin Cc: Alexander Potapenko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/kasan/kasan.c | 3 ++- mm/kasan/kasan.h | 2 +- mm/kasan/report.c | 30 ++++++++++++++---------------- 3 files changed, 17 insertions(+), 18 deletions(-) diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c index 98b27195e38b..9348d27088c1 100644 --- a/mm/kasan/kasan.c +++ b/mm/kasan/kasan.c @@ -577,7 +577,8 @@ bool kasan_slab_free(struct kmem_cache *cache, void *object) shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object)); if (shadow_byte < 0 || shadow_byte >= KASAN_SHADOW_SCALE_SIZE) { - kasan_report_double_free(cache, object, shadow_byte); + kasan_report_double_free(cache, object, + __builtin_return_address(1)); return true; } diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index dd2dea8eb077..1229298cce64 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -99,7 +99,7 @@ static inline const void *kasan_shadow_to_mem(const void *shadow_addr) void kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip); void kasan_report_double_free(struct kmem_cache *cache, void *object, - s8 shadow); + void *ip); #if defined(CONFIG_SLAB) || defined(CONFIG_SLUB) void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache); diff --git a/mm/kasan/report.c b/mm/kasan/report.c index b015acc80876..7d3d9670e233 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c @@ -243,22 +243,8 @@ static void describe_object(struct kmem_cache *cache, void *object, describe_object_addr(cache, object, addr); } -void kasan_report_double_free(struct kmem_cache *cache, void *object, - s8 shadow) -{ - unsigned long flags; - - kasan_start_report(&flags); - pr_err("BUG: Double free or freeing an invalid pointer\n"); - pr_err("Unexpected shadow byte: 0x%hhX\n", shadow); - dump_stack(); - describe_object(cache, object, NULL); - kasan_end_report(&flags); -} - -static void print_address_description(struct kasan_access_info *info) +static void print_address_description(void *addr) { - void *addr = (void *)info->access_addr; struct page *page = addr_to_page(addr); dump_stack(); @@ -333,6 +319,18 @@ static void print_shadow_for_address(const void *addr) } } +void kasan_report_double_free(struct kmem_cache *cache, void *object, + void *ip) +{ + unsigned long flags; + + kasan_start_report(&flags); + pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", ip); + print_address_description(object); + print_shadow_for_address(object); + kasan_end_report(&flags); +} + static void kasan_report_error(struct kasan_access_info *info) { unsigned long flags; @@ -344,7 +342,7 @@ static void kasan_report_error(struct kasan_access_info *info) if (!addr_has_shadow(info)) { dump_stack(); } else { - print_address_description(info); + print_address_description((void *)info->access_addr); print_shadow_for_address(info->first_bad_addr); } -- 2.20.1