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authorJoonsoo Kim <iamjoonsoo.kim@lge.com>2016-03-15 14:55:12 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-03-15 16:55:16 -0700
commitd86bd1bece6fc41d59253002db5441fe960a37f6 (patch)
tree3881125eb61ec76b5ad87d6a7e9f51061b76e7e6 /mm/slub.c
parent149daaf3a02c020ddae64668c3a1bd0c4f314d6a (diff)
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mm/slub: support left redzone
SLUB already has a redzone debugging feature. But it is only positioned at the end of object (aka right redzone) so it cannot catch left oob. Although current object's right redzone acts as left redzone of next object, first object in a slab cannot take advantage of this effect. This patch explicitly adds a left red zone to each object to detect left oob more precisely. Background: Someone complained to me that left OOB doesn't catch even if KASAN is enabled which does page allocation debugging. That page is out of our control so it would be allocated when left OOB happens and, in this case, we can't find OOB. Moreover, SLUB debugging feature can be enabled without page allocator debugging and, in this case, we will miss that OOB. Before trying to implement, I expected that changes would be too complex, but, it doesn't look that complex to me now. Almost changes are applied to debug specific functions so I feel okay. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slub.c')
-rw-r--r--mm/slub.c100
1 files changed, 71 insertions, 29 deletions
diff --git a/mm/slub.c b/mm/slub.c
index c2a227d8a4ee..2d4d817f3d7a 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -124,6 +124,14 @@ static inline int kmem_cache_debug(struct kmem_cache *s)
#endif
}
+static inline void *fixup_red_left(struct kmem_cache *s, void *p)
+{
+ if (kmem_cache_debug(s) && s->flags & SLAB_RED_ZONE)
+ p += s->red_left_pad;
+
+ return p;
+}
+
static inline bool kmem_cache_has_cpu_partial(struct kmem_cache *s)
{
#ifdef CONFIG_SLUB_CPU_PARTIAL
@@ -232,24 +240,6 @@ static inline void stat(const struct kmem_cache *s, enum stat_item si)
* Core slab cache functions
*******************************************************************/
-/* Verify that a pointer has an address that is valid within a slab page */
-static inline int check_valid_pointer(struct kmem_cache *s,
- struct page *page, const void *object)
-{
- void *base;
-
- if (!object)
- return 1;
-
- base = page_address(page);
- if (object < base || object >= base + page->objects * s->size ||
- (object - base) % s->size) {
- return 0;
- }
-
- return 1;
-}
-
static inline void *get_freepointer(struct kmem_cache *s, void *object)
{
return *(void **)(object + s->offset);
@@ -279,12 +269,14 @@ static inline void set_freepointer(struct kmem_cache *s, void *object, void *fp)
/* Loop over all objects in a slab */
#define for_each_object(__p, __s, __addr, __objects) \
- for (__p = (__addr); __p < (__addr) + (__objects) * (__s)->size;\
- __p += (__s)->size)
+ for (__p = fixup_red_left(__s, __addr); \
+ __p < (__addr) + (__objects) * (__s)->size; \
+ __p += (__s)->size)
#define for_each_object_idx(__p, __idx, __s, __addr, __objects) \
- for (__p = (__addr), __idx = 1; __idx <= __objects;\
- __p += (__s)->size, __idx++)
+ for (__p = fixup_red_left(__s, __addr), __idx = 1; \
+ __idx <= __objects; \
+ __p += (__s)->size, __idx++)
/* Determine object index from a given position */
static inline int slab_index(void *p, struct kmem_cache *s, void *addr)
@@ -442,6 +434,22 @@ static void get_map(struct kmem_cache *s, struct page *page, unsigned long *map)
set_bit(slab_index(p, s, addr), map);
}
+static inline int size_from_object(struct kmem_cache *s)
+{
+ if (s->flags & SLAB_RED_ZONE)
+ return s->size - s->red_left_pad;
+
+ return s->size;
+}
+
+static inline void *restore_red_left(struct kmem_cache *s, void *p)
+{
+ if (s->flags & SLAB_RED_ZONE)
+ p -= s->red_left_pad;
+
+ return p;
+}
+
/*
* Debug settings:
*/
@@ -475,6 +483,26 @@ static inline void metadata_access_disable(void)
/*
* Object debugging
*/
+
+/* Verify that a pointer has an address that is valid within a slab page */
+static inline int check_valid_pointer(struct kmem_cache *s,
+ struct page *page, void *object)
+{
+ void *base;
+
+ if (!object)
+ return 1;
+
+ base = page_address(page);
+ object = restore_red_left(s, object);
+ if (object < base || object >= base + page->objects * s->size ||
+ (object - base) % s->size) {
+ return 0;
+ }
+
+ return 1;
+}
+
static void print_section(char *text, u8 *addr, unsigned int length)
{
metadata_access_enable();
@@ -614,7 +642,9 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
pr_err("INFO: Object 0x%p @offset=%tu fp=0x%p\n\n",
p, p - addr, get_freepointer(s, p));
- if (p > addr + 16)
+ if (s->flags & SLAB_RED_ZONE)
+ print_section("Redzone ", p - s->red_left_pad, s->red_left_pad);
+ else if (p > addr + 16)
print_section("Bytes b4 ", p - 16, 16);
print_section("Object ", p, min_t(unsigned long, s->object_size,
@@ -631,9 +661,9 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
if (s->flags & SLAB_STORE_USER)
off += 2 * sizeof(struct track);
- if (off != s->size)
+ if (off != size_from_object(s))
/* Beginning of the filler is the free pointer */
- print_section("Padding ", p + off, s->size - off);
+ print_section("Padding ", p + off, size_from_object(s) - off);
dump_stack();
}
@@ -663,6 +693,9 @@ static void init_object(struct kmem_cache *s, void *object, u8 val)
{
u8 *p = object;
+ if (s->flags & SLAB_RED_ZONE)
+ memset(p - s->red_left_pad, val, s->red_left_pad);
+
if (s->flags & __OBJECT_POISON) {
memset(p, POISON_FREE, s->object_size - 1);
p[s->object_size - 1] = POISON_END;
@@ -755,11 +788,11 @@ static int check_pad_bytes(struct kmem_cache *s, struct page *page, u8 *p)
/* We also have user information there */
off += 2 * sizeof(struct track);
- if (s->size == off)
+ if (size_from_object(s) == off)
return 1;
return check_bytes_and_report(s, page, p, "Object padding",
- p + off, POISON_INUSE, s->size - off);
+ p + off, POISON_INUSE, size_from_object(s) - off);
}
/* Check the pad bytes at the end of a slab page */
@@ -804,6 +837,10 @@ static int check_object(struct kmem_cache *s, struct page *page,
if (s->flags & SLAB_RED_ZONE) {
if (!check_bytes_and_report(s, page, object, "Redzone",
+ object - s->red_left_pad, val, s->red_left_pad))
+ return 0;
+
+ if (!check_bytes_and_report(s, page, object, "Redzone",
endobject, val, s->inuse - s->object_size))
return 0;
} else {
@@ -1445,7 +1482,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
set_freepointer(s, p, NULL);
}
- page->freelist = start;
+ page->freelist = fixup_red_left(s, start);
page->inuse = page->objects;
page->frozen = 1;
@@ -3274,7 +3311,7 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order)
*/
size += 2 * sizeof(struct track);
- if (flags & SLAB_RED_ZONE)
+ if (flags & SLAB_RED_ZONE) {
/*
* Add some empty padding so that we can catch
* overwrites from earlier objects rather than let
@@ -3283,6 +3320,11 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order)
* of the object.
*/
size += sizeof(void *);
+
+ s->red_left_pad = sizeof(void *);
+ s->red_left_pad = ALIGN(s->red_left_pad, s->align);
+ size += s->red_left_pad;
+ }
#endif
/*