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kasan: detect invalid frees for large objects

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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 <[email protected]>
Cc: Andrey Ryabinin <[email protected]>a
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Dmitry Vyukov 2018-02-06 15:36:23 -08:00 • committed by Linus Torvalds
commit 47adccce3e
6 changed files with 44 additions and 15 deletions
Download patch file Download diff file Expand all files Collapse all files

4
mm/slub.c
View file

@ -1356,7 +1356,7 @@ static inline void kmalloc_large_node_hook(void *ptr, size_t size, gfp_t flags)
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;
}