From: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Subject: kasan: detect invalid frees for large objects Patch series "kasan: detect invalid frees". KASAN detects double-frees, but does not detect invalid-frees (when a pointer into a middle of heap object is passed to free). We recently had a very unpleasant case in crypto code which freed an inner object inside of a heap allocation. This left unnoticed during free, but totally corrupted heap and later lead to a bunch of random crashes all over kernel code. Detect invalid frees. This patch (of 5): Detect frees of pointers into middle of large heap objects. I dropped const from kasan_kfree_large() because it starts propagating through a bunch of functions in kasan_report.c, slab/slub nearest_obj(), all of their local variables, fixup_red_left(), etc. Link: http://lkml.kernel.org/r/1b45b4fe1d20fc0de1329aab674c1dd973fee723.1514378558.git.dvyukov@xxxxxxxxxx Signed-off-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>a Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/kasan.h | 4 ++-- lib/test_kasan.c | 33 +++++++++++++++++++++++++++++++++ mm/kasan/kasan.c | 12 +++++------- mm/kasan/kasan.h | 3 +-- mm/kasan/report.c | 3 +-- mm/slub.c | 4 ++-- 6 files changed, 44 insertions(+), 15 deletions(-) diff -puN include/linux/kasan.h~kasan-detect-invalid-frees-for-large-objects include/linux/kasan.h --- a/include/linux/kasan.h~kasan-detect-invalid-frees-for-large-objects +++ a/include/linux/kasan.h @@ -56,7 +56,7 @@ void kasan_poison_object_data(struct kme void kasan_init_slab_obj(struct kmem_cache *cache, const void *object); void kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags); -void kasan_kfree_large(const void *ptr); +void kasan_kfree_large(void *ptr); void kasan_poison_kfree(void *ptr); void kasan_kmalloc(struct kmem_cache *s, const void *object, size_t size, gfp_t flags); @@ -108,7 +108,7 @@ static inline void kasan_init_slab_obj(s const void *object) {} static inline void kasan_kmalloc_large(void *ptr, size_t size, gfp_t flags) {} -static inline void kasan_kfree_large(const void *ptr) {} +static inline void kasan_kfree_large(void *ptr) {} static inline void kasan_poison_kfree(void *ptr) {} static inline void kasan_kmalloc(struct kmem_cache *s, const void *object, size_t size, gfp_t flags) {} diff -puN lib/test_kasan.c~kasan-detect-invalid-frees-for-large-objects lib/test_kasan.c --- a/lib/test_kasan.c~kasan-detect-invalid-frees-for-large-objects +++ a/lib/test_kasan.c @@ -94,6 +94,37 @@ static noinline void __init kmalloc_page ptr[size] = 0; kfree(ptr); } + +static noinline void __init kmalloc_pagealloc_uaf(void) +{ + char *ptr; + size_t size = KMALLOC_MAX_CACHE_SIZE + 10; + + pr_info("kmalloc pagealloc allocation: use-after-free\n"); + ptr = kmalloc(size, GFP_KERNEL); + if (!ptr) { + pr_err("Allocation failed\n"); + return; + } + + kfree(ptr); + ptr[0] = 0; +} + +static noinline void __init kmalloc_pagealloc_invalid_free(void) +{ + char *ptr; + size_t size = KMALLOC_MAX_CACHE_SIZE + 10; + + pr_info("kmalloc pagealloc allocation: invalid-free\n"); + ptr = kmalloc(size, GFP_KERNEL); + if (!ptr) { + pr_err("Allocation failed\n"); + return; + } + + kfree(ptr + 1); +} #endif static noinline void __init kmalloc_large_oob_right(void) @@ -505,6 +536,8 @@ static int __init kmalloc_tests_init(voi kmalloc_node_oob_right(); #ifdef CONFIG_SLUB kmalloc_pagealloc_oob_right(); + kmalloc_pagealloc_uaf(); + kmalloc_pagealloc_invalid_free(); #endif kmalloc_large_oob_right(); kmalloc_oob_krealloc_more(); diff -puN mm/kasan/kasan.c~kasan-detect-invalid-frees-for-large-objects mm/kasan/kasan.c --- a/mm/kasan/kasan.c~kasan-detect-invalid-frees-for-large-objects +++ a/mm/kasan/kasan.c @@ -511,8 +511,7 @@ bool kasan_slab_free(struct kmem_cache * 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, - __builtin_return_address(1)); + kasan_report_invalid_free(object, __builtin_return_address(1)); return true; } @@ -602,12 +601,11 @@ void kasan_poison_kfree(void *ptr) kasan_poison_slab_free(page->slab_cache, ptr); } -void kasan_kfree_large(const void *ptr) +void kasan_kfree_large(void *ptr) { - struct page *page = virt_to_page(ptr); - - kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page), - KASAN_FREE_PAGE); + if (ptr != page_address(virt_to_head_page(ptr))) + kasan_report_invalid_free(ptr, __builtin_return_address(1)); + /* The object will be poisoned by page_alloc. */ } int kasan_module_alloc(void *addr, size_t size) diff -puN mm/kasan/kasan.h~kasan-detect-invalid-frees-for-large-objects mm/kasan/kasan.h --- a/mm/kasan/kasan.h~kasan-detect-invalid-frees-for-large-objects +++ a/mm/kasan/kasan.h @@ -107,8 +107,7 @@ static inline const void *kasan_shadow_t 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, - void *ip); +void kasan_report_invalid_free(void *object, void *ip); #if defined(CONFIG_SLAB) || defined(CONFIG_SLUB) void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache); diff -puN mm/kasan/report.c~kasan-detect-invalid-frees-for-large-objects mm/kasan/report.c --- a/mm/kasan/report.c~kasan-detect-invalid-frees-for-large-objects +++ a/mm/kasan/report.c @@ -326,8 +326,7 @@ static void print_shadow_for_address(con } } -void kasan_report_double_free(struct kmem_cache *cache, void *object, - void *ip) +void kasan_report_invalid_free(void *object, void *ip) { unsigned long flags; diff -puN mm/slub.c~kasan-detect-invalid-frees-for-large-objects mm/slub.c --- a/mm/slub.c~kasan-detect-invalid-frees-for-large-objects +++ a/mm/slub.c @@ -1356,7 +1356,7 @@ static inline void kmalloc_large_node_ho kasan_kmalloc_large(ptr, size, flags); } -static inline void kfree_hook(const void *x) +static inline void kfree_hook(void *x) { kmemleak_free(x); kasan_kfree_large(x); @@ -3910,7 +3910,7 @@ void kfree(const void *x) page = virt_to_head_page(x); if (unlikely(!PageSlab(page))) { BUG_ON(!PageCompound(page)); - kfree_hook(x); + kfree_hook(object); __free_pages(page, compound_order(page)); return; } _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
