From 6860f6340c0918cddcd3c9fcf8c36401c8184268 Mon Sep 17 00:00:00 2001 From: Dmitry Vyukov Date: Tue, 6 Feb 2018 15:36:30 -0800 Subject: [PATCH] kasan: detect invalid frees for large mempool objects Detect frees of pointers into middle of mempool objects. I did a one-off test, but it turned out to be very tricky, so I reverted it. First, mempool does not call kasan_poison_kfree() unless allocation function fails. I stubbed an allocation function to fail on second and subsequent allocations. But then mempool stopped to call kasan_poison_kfree() at all, because it does it only when allocation function is mempool_kmalloc(). We could support this special failing test allocation function in mempool, but it also can't live with kasan tests, because these are in a module. Link: http://lkml.kernel.org/r/bf7a7d035d7a5ed62d2dd0e3d2e8a4fcdf456aa7.1514378558.git.dvyukov@google.com Signed-off-by: Dmitry Vyukov Cc: Andrey Ryabinin a Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kasan.h | 4 ++-- mm/kasan/kasan.c | 11 ++++++++--- mm/mempool.c | 6 +++--- 3 files changed, 13 insertions(+), 8 deletions(-) diff --git a/include/linux/kasan.h b/include/linux/kasan.h index f0d13c3..fc45f89 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -57,7 +57,7 @@ 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(void *ptr, unsigned long ip); -void kasan_poison_kfree(void *ptr); +void kasan_poison_kfree(void *ptr, unsigned long ip); void kasan_kmalloc(struct kmem_cache *s, const void *object, size_t size, gfp_t flags); void kasan_krealloc(const void *object, size_t new_size, gfp_t flags); @@ -109,7 +109,7 @@ static inline void kasan_init_slab_obj(struct kmem_cache *cache, static inline void kasan_kmalloc_large(void *ptr, size_t size, gfp_t flags) {} static inline void kasan_kfree_large(void *ptr, unsigned long ip) {} -static inline void kasan_poison_kfree(void *ptr) {} +static inline void kasan_poison_kfree(void *ptr, unsigned long ip) {} static inline void kasan_kmalloc(struct kmem_cache *s, const void *object, size_t size, gfp_t flags) {} static inline void kasan_krealloc(const void *object, size_t new_size, diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c index 32f555d..77c1037 100644 --- a/mm/kasan/kasan.c +++ b/mm/kasan/kasan.c @@ -588,17 +588,22 @@ void kasan_krealloc(const void *object, size_t size, gfp_t flags) kasan_kmalloc(page->slab_cache, object, size, flags); } -void kasan_poison_kfree(void *ptr) +void kasan_poison_kfree(void *ptr, unsigned long ip) { struct page *page; page = virt_to_head_page(ptr); - if (unlikely(!PageSlab(page))) + if (unlikely(!PageSlab(page))) { + if (ptr != page_address(page)) { + kasan_report_invalid_free(ptr, ip); + return; + } kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page), KASAN_FREE_PAGE); - else + } else { kasan_poison_slab_free(page->slab_cache, ptr); + } } void kasan_kfree_large(void *ptr, unsigned long ip) diff --git a/mm/mempool.c b/mm/mempool.c index 7d8c5a0..5c9dce3 100644 --- a/mm/mempool.c +++ b/mm/mempool.c @@ -103,10 +103,10 @@ static inline void poison_element(mempool_t *pool, void *element) } #endif /* CONFIG_DEBUG_SLAB || CONFIG_SLUB_DEBUG_ON */ -static void kasan_poison_element(mempool_t *pool, void *element) +static __always_inline void kasan_poison_element(mempool_t *pool, void *element) { if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc) - kasan_poison_kfree(element); + kasan_poison_kfree(element, _RET_IP_); if (pool->alloc == mempool_alloc_pages) kasan_free_pages(element, (unsigned long)pool->pool_data); } @@ -119,7 +119,7 @@ static void kasan_unpoison_element(mempool_t *pool, void *element, gfp_t flags) kasan_alloc_pages(element, (unsigned long)pool->pool_data); } -static void add_element(mempool_t *pool, void *element) +static __always_inline void add_element(mempool_t *pool, void *element) { BUG_ON(pool->curr_nr >= pool->min_nr); poison_element(pool, element); -- 2.7.4