From: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> Subject: kasan: record and print the free track Move free track from kasan_alloc_meta to kasan_free_meta in order to make struct kasan_alloc_meta and kasan_free_meta size are both 16 bytes. It is a good size because it is the minimal redzone size and a good number of alignment. For free track, we make some modifications as shown below: 1) Remove the free_track from struct kasan_alloc_meta. 2) Add the free_track into struct kasan_free_meta. 3) Add a macro KASAN_KMALLOC_FREETRACK in order to check whether it can print free stack in KASAN report. [1]https://bugzilla.kernel.org/show_bug.cgi?id=198437 [walter-zh.wu@xxxxxxxxxxxx: build fix] Link: http://lkml.kernel.org/r/20200710162440.23887-1-walter-zh.wu@xxxxxxxxxxxx Link: http://lkml.kernel.org/r/20200601051022.1230-1-walter-zh.wu@xxxxxxxxxxxx Signed-off-by: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> Suggested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Co-developed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Tested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> Cc: Jonathan Corbet <corbet@xxxxxxx> Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx> Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx> Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> Cc: Matthias Brugger <matthias.bgg@xxxxxxxxx> Cc: "Paul E . McKenney" <paulmck@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/kasan/common.c | 22 +-------------------- mm/kasan/generic.c | 22 +++++++++++++++++++++ mm/kasan/generic_report.c | 1 mm/kasan/kasan.h | 16 ++++++++++++--- mm/kasan/quarantine.c | 1 mm/kasan/report.c | 26 +++---------------------- mm/kasan/tags.c | 37 ++++++++++++++++++++++++++++++++++++ 7 files changed, 80 insertions(+), 45 deletions(-) --- a/mm/kasan/common.c~kasan-record-and-print-the-free-track +++ a/mm/kasan/common.c @@ -50,7 +50,7 @@ depot_stack_handle_t kasan_save_stack(gf return stack_depot_save(entries, nr_entries, flags); } -static inline void set_track(struct kasan_track *track, gfp_t flags) +void kasan_set_track(struct kasan_track *track, gfp_t flags) { track->pid = current->pid; track->stack = kasan_save_stack(flags); @@ -298,24 +298,6 @@ struct kasan_free_meta *get_free_info(st return (void *)object + cache->kasan_info.free_meta_offset; } - -static void kasan_set_free_info(struct kmem_cache *cache, - void *object, u8 tag) -{ - struct kasan_alloc_meta *alloc_meta; - u8 idx = 0; - - alloc_meta = get_alloc_info(cache, object); - -#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY - idx = alloc_meta->free_track_idx; - alloc_meta->free_pointer_tag[idx] = tag; - alloc_meta->free_track_idx = (idx + 1) % KASAN_NR_FREE_STACKS; -#endif - - set_track(&alloc_meta->free_track[idx], GFP_NOWAIT); -} - void kasan_poison_slab(struct page *page) { unsigned long i; @@ -491,7 +473,7 @@ static void *__kasan_kmalloc(struct kmem KASAN_KMALLOC_REDZONE); if (cache->flags & SLAB_KASAN) - set_track(&get_alloc_info(cache, object)->alloc_track, flags); + kasan_set_track(&get_alloc_info(cache, object)->alloc_track, flags); return set_tag(object, tag); } --- a/mm/kasan/generic.c~kasan-record-and-print-the-free-track +++ a/mm/kasan/generic.c @@ -345,3 +345,25 @@ void kasan_record_aux_stack(void *addr) alloc_info->aux_stack[1] = alloc_info->aux_stack[0]; alloc_info->aux_stack[0] = kasan_save_stack(GFP_NOWAIT); } + +void kasan_set_free_info(struct kmem_cache *cache, + void *object, u8 tag) +{ + struct kasan_free_meta *free_meta; + + free_meta = get_free_info(cache, object); + kasan_set_track(&free_meta->free_track, GFP_NOWAIT); + + /* + * the object was freed and has free track set + */ + *(u8 *)kasan_mem_to_shadow(object) = KASAN_KMALLOC_FREETRACK; +} + +struct kasan_track *kasan_get_free_track(struct kmem_cache *cache, + void *object, u8 tag) +{ + if (*(u8 *)kasan_mem_to_shadow(object) != KASAN_KMALLOC_FREETRACK) + return NULL; + return &get_free_info(cache, object)->free_track; +} --- a/mm/kasan/generic_report.c~kasan-record-and-print-the-free-track +++ a/mm/kasan/generic_report.c @@ -80,6 +80,7 @@ static const char *get_shadow_bug_type(s break; case KASAN_FREE_PAGE: case KASAN_KMALLOC_FREE: + case KASAN_KMALLOC_FREETRACK: bug_type = "use-after-free"; break; case KASAN_ALLOCA_LEFT: --- a/mm/kasan/kasan.h~kasan-record-and-print-the-free-track +++ a/mm/kasan/kasan.h @@ -17,15 +17,17 @@ #define KASAN_PAGE_REDZONE 0xFE /* redzone for kmalloc_large allocations */ #define KASAN_KMALLOC_REDZONE 0xFC /* redzone inside slub object */ #define KASAN_KMALLOC_FREE 0xFB /* object was freed (kmem_cache_free/kfree) */ +#define KASAN_KMALLOC_FREETRACK 0xFA /* object was freed and has free track set */ #else #define KASAN_FREE_PAGE KASAN_TAG_INVALID #define KASAN_PAGE_REDZONE KASAN_TAG_INVALID #define KASAN_KMALLOC_REDZONE KASAN_TAG_INVALID #define KASAN_KMALLOC_FREE KASAN_TAG_INVALID +#define KASAN_KMALLOC_FREETRACK KASAN_TAG_INVALID #endif -#define KASAN_GLOBAL_REDZONE 0xFA /* redzone for global variable */ -#define KASAN_VMALLOC_INVALID 0xF9 /* unallocated space in vmapped page */ +#define KASAN_GLOBAL_REDZONE 0xF9 /* redzone for global variable */ +#define KASAN_VMALLOC_INVALID 0xF8 /* unallocated space in vmapped page */ /* * Stack redzone shadow values @@ -110,8 +112,9 @@ struct kasan_alloc_meta { * The free stack is stored into struct kasan_free_meta. */ depot_stack_handle_t aux_stack[2]; -#endif +#else struct kasan_track free_track[KASAN_NR_FREE_STACKS]; +#endif #ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY u8 free_pointer_tag[KASAN_NR_FREE_STACKS]; u8 free_track_idx; @@ -126,6 +129,9 @@ struct kasan_free_meta { * Otherwise it might be used for the allocator freelist. */ struct qlist_node quarantine_link; +#ifdef CONFIG_KASAN_GENERIC + struct kasan_track free_track; +#endif }; struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache, @@ -167,6 +173,10 @@ void kasan_report_invalid_free(void *obj struct page *kasan_addr_to_page(const void *addr); depot_stack_handle_t kasan_save_stack(gfp_t flags); +void kasan_set_track(struct kasan_track *track, gfp_t flags); +void kasan_set_free_info(struct kmem_cache *cache, void *object, u8 tag); +struct kasan_track *kasan_get_free_track(struct kmem_cache *cache, + void *object, u8 tag); #if defined(CONFIG_KASAN_GENERIC) && \ (defined(CONFIG_SLAB) || defined(CONFIG_SLUB)) --- a/mm/kasan/quarantine.c~kasan-record-and-print-the-free-track +++ a/mm/kasan/quarantine.c @@ -145,6 +145,7 @@ static void qlink_free(struct qlist_node if (IS_ENABLED(CONFIG_SLAB)) local_irq_save(flags); + *(u8 *)kasan_mem_to_shadow(object) = KASAN_KMALLOC_FREE; ___cache_free(cache, object, _THIS_IP_); if (IS_ENABLED(CONFIG_SLAB)) --- a/mm/kasan/report.c~kasan-record-and-print-the-free-track +++ a/mm/kasan/report.c @@ -165,26 +165,6 @@ static void describe_object_addr(struct (void *)(object_addr + cache->object_size)); } -static struct kasan_track *kasan_get_free_track(struct kmem_cache *cache, - void *object, u8 tag) -{ - struct kasan_alloc_meta *alloc_meta; - int i = 0; - - alloc_meta = get_alloc_info(cache, object); - -#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY - for (i = 0; i < KASAN_NR_FREE_STACKS; i++) { - if (alloc_meta->free_pointer_tag[i] == tag) - break; - } - if (i == KASAN_NR_FREE_STACKS) - i = alloc_meta->free_track_idx; -#endif - - return &alloc_meta->free_track[i]; -} - static void describe_object(struct kmem_cache *cache, void *object, const void *addr, u8 tag) { @@ -196,8 +176,10 @@ static void describe_object(struct kmem_ print_track(&alloc_info->alloc_track, "Allocated"); pr_err("\n"); free_track = kasan_get_free_track(cache, object, tag); - print_track(free_track, "Freed"); - pr_err("\n"); + if (free_track) { + print_track(free_track, "Freed"); + pr_err("\n"); + } #ifdef CONFIG_KASAN_GENERIC if (alloc_info->aux_stack[0]) { --- a/mm/kasan/tags.c~kasan-record-and-print-the-free-track +++ a/mm/kasan/tags.c @@ -161,3 +161,40 @@ void __hwasan_tag_memory(unsigned long a kasan_poison_shadow((void *)addr, size, tag); } EXPORT_SYMBOL(__hwasan_tag_memory); + +void kasan_set_free_info(struct kmem_cache *cache, + void *object, u8 tag) +{ + struct kasan_alloc_meta *alloc_meta; + u8 idx = 0; + + alloc_meta = get_alloc_info(cache, object); + +#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY + idx = alloc_meta->free_track_idx; + alloc_meta->free_pointer_tag[idx] = tag; + alloc_meta->free_track_idx = (idx + 1) % KASAN_NR_FREE_STACKS; +#endif + + kasan_set_track(&alloc_meta->free_track[idx], GFP_NOWAIT); +} + +struct kasan_track *kasan_get_free_track(struct kmem_cache *cache, + void *object, u8 tag) +{ + struct kasan_alloc_meta *alloc_meta; + int i = 0; + + alloc_meta = get_alloc_info(cache, object); + +#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY + for (i = 0; i < KASAN_NR_FREE_STACKS; i++) { + if (alloc_meta->free_pointer_tag[i] == tag) + break; + } + if (i == KASAN_NR_FREE_STACKS) + i = alloc_meta->free_track_idx; +#endif + + return &alloc_meta->free_track[i]; +} _
