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Subject[PATCH 1/5] kasan: fix assigning tags twice
Date
When an object is kmalloc()'ed, two hooks are called: kasan_slab_alloc()
and kasan_kmalloc(). Right now we assign a tag twice, once in each of
the hooks. Fix it by assigning a tag only in the former hook.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
mm/kasan/common.c | 29 +++++++++++++++++------------
1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 73c9cbfdedf4..09b534fbba17 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -361,10 +361,15 @@ void kasan_poison_object_data(struct kmem_cache *cache, void *object)
* get different tags.
*/
static u8 assign_tag(struct kmem_cache *cache, const void *object,
- bool init, bool krealloc)
+ bool init, bool keep_tag)
{
- /* Reuse the same tag for krealloc'ed objects. */
- if (krealloc)
+ /*
+ * 1. When an object is kmalloc()'ed, two hooks are called:
+ * kasan_slab_alloc() and kasan_kmalloc(). We assign the
+ * tag only in the first one.
+ * 2. We reuse the same tag for krealloc'ed objects.
+ */
+ if (keep_tag)
return get_tag(object);

/*
@@ -405,12 +410,6 @@ void * __must_check kasan_init_slab_obj(struct kmem_cache *cache,
return (void *)object;
}

-void * __must_check kasan_slab_alloc(struct kmem_cache *cache, void *object,
- gfp_t flags)
-{
- return kasan_kmalloc(cache, object, cache->object_size, flags);
-}
-
static inline bool shadow_invalid(u8 tag, s8 shadow_byte)
{
if (IS_ENABLED(CONFIG_KASAN_GENERIC))
@@ -467,7 +466,7 @@ bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
}

static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object,
- size_t size, gfp_t flags, bool krealloc)
+ size_t size, gfp_t flags, bool keep_tag)
{
unsigned long redzone_start;
unsigned long redzone_end;
@@ -485,7 +484,7 @@ static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object,
KASAN_SHADOW_SCALE_SIZE);

if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
- tag = assign_tag(cache, object, false, krealloc);
+ tag = assign_tag(cache, object, false, keep_tag);

/* Tag is ignored in set_tag without CONFIG_KASAN_SW_TAGS */
kasan_unpoison_shadow(set_tag(object, tag), size);
@@ -498,10 +497,16 @@ static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object,
return set_tag(object, tag);
}

+void * __must_check kasan_slab_alloc(struct kmem_cache *cache, void *object,
+ gfp_t flags)
+{
+ return __kasan_kmalloc(cache, object, cache->object_size, flags, false);
+}
+
void * __must_check kasan_kmalloc(struct kmem_cache *cache, const void *object,
size_t size, gfp_t flags)
{
- return __kasan_kmalloc(cache, object, size, flags, false);
+ return __kasan_kmalloc(cache, object, size, flags, true);
}
EXPORT_SYMBOL(kasan_kmalloc);

--
2.20.1.791.gb4d0f1c61a-goog
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