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kasan: detect invalid frees for large mempool objects

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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 <[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 15:36:30 -08:00 • committed by Linus Torvalds
commit 6860f6340c
3 changed files with 13 additions and 8 deletions
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11
mm/kasan/kasan.c
View file

@ -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)

6
mm/mempool.c
View file

@ -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);