Commit 47adccce authored by Dmitry Vyukov's avatar Dmitry Vyukov Committed by Linus Torvalds

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.comSigned-off-by: default avatarDmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>a
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d321599c
......@@ -56,7 +56,7 @@ void kasan_poison_object_data(struct kmem_cache *cache, void *object);
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(const void *ptr);
void kasan_kfree_large(void *ptr);
void kasan_poison_kfree(void *ptr);
void kasan_kmalloc(struct kmem_cache *s, const void *object, size_t size,
gfp_t flags);
......@@ -108,7 +108,7 @@ static inline void kasan_init_slab_obj(struct kmem_cache *cache,
const void *object) {}
static inline void kasan_kmalloc_large(void *ptr, size_t size, gfp_t flags) {}
static inline void kasan_kfree_large(const void *ptr) {}
static inline void kasan_kfree_large(void *ptr) {}
static inline void kasan_poison_kfree(void *ptr) {}
static inline void kasan_kmalloc(struct kmem_cache *s, const void *object,
size_t size, gfp_t flags) {}
......
......@@ -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();
......
......@@ -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)
......
......@@ -107,8 +107,7 @@ static inline const void *kasan_shadow_to_mem(const void *shadow_addr)
void kasan_report(unsigned long addr, size_t size,
bool is_write, unsigned long ip);
void kasan_report_double_free(struct kmem_cache *cache, void *object,
void *ip);
void kasan_report_invalid_free(void *object, void *ip);
#if defined(CONFIG_SLAB) || defined(CONFIG_SLUB)
void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache);
......
......@@ -326,8 +326,7 @@ static void print_shadow_for_address(const void *addr)
}
}
void kasan_report_double_free(struct kmem_cache *cache, void *object,
void *ip)
void kasan_report_invalid_free(void *object, void *ip)
{
unsigned long flags;
......
......@@ -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;
}
......
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