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 --- lib/test_kasan.c | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) (limited to 'lib/test_kasan.c') diff --git a/lib/test_kasan.c b/lib/test_kasan.c index 2724f86c4cef..e9c5d765be66 100644 --- a/lib/test_kasan.c +++ b/lib/test_kasan.c @@ -94,6 +94,37 @@ static noinline void __init kmalloc_pagealloc_oob_right(void) 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(void) 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(); -- cgit v1.2.3-59-g8ed1b