From 47adccce3e8a31d315f47183ab1185862b2fc5d4 Mon Sep 17 00:00:00 2001 From: Dmitry Vyukov Date: Tue, 6 Feb 2018 15:36:23 -0800 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@google.com Signed-off-by: Dmitry Vyukov Cc: Andrey Ryabinin a Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/kasan/kasan.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) (limited to 'mm/kasan/kasan.c') diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c index 8aaee42fcfab..ecb64fda79e6 100644 --- a/mm/kasan/kasan.c +++ b/mm/kasan/kasan.c @@ -511,8 +511,7 @@ 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, - __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) -- cgit v1.2.3