kasan: fix assigning tags twice

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.

Link: http://lkml.kernel.org/r/ce8c6431da735aa7ec051fd6497153df690eb021.1549921721.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgeniy Stepanov <eugenis@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kostya Serebryany <kcc@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Qian Cai <cai@lca.pw>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 73c9cbf..09b534f 100644 (file)
--- 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);