summaryrefslogtreecommitdiff
path: root/mm/slub.c
diff options
context:
space:
mode:
authorFeng Tang <feng.tang@intel.com>2022-10-21 06:24:05 +0300
committerVlastimil Babka <vbabka@suse.cz>2022-11-11 11:06:33 +0300
commit946fa0dbf2d8923a587f7348adf16563d59f1b3d (patch)
tree413f5ec2ce519fe520fda41eeeb56a3517252bfc /mm/slub.c
parent5d1ba31087627423dfb2bd87badd62361701997b (diff)
downloadlinux-946fa0dbf2d8923a587f7348adf16563d59f1b3d.tar.xz
mm/slub: extend redzone check to extra allocated kmalloc space than requested
kmalloc will round up the request size to a fixed size (mostly power of 2), so there could be a extra space than what is requested, whose size is the actual buffer size minus original request size. To better detect out of bound access or abuse of this space, add redzone sanity check for it. In current kernel, some kmalloc user already knows the existence of the space and utilizes it after calling 'ksize()' to know the real size of the allocated buffer. So we skip the sanity check for objects which have been called with ksize(), as treating them as legitimate users. Kees Cook is working on sanitizing all these user cases, by using kmalloc_size_roundup() to avoid ambiguous usages. And after this is done, this special handling for ksize() can be removed. In some cases, the free pointer could be saved inside the latter part of object data area, which may overlap the redzone part(for small sizes of kmalloc objects). As suggested by Hyeonggon Yoo, force the free pointer to be in meta data area when kmalloc redzone debug is enabled, to make all kmalloc objects covered by redzone check. Suggested-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Feng Tang <feng.tang@intel.com> Acked-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Diffstat (limited to 'mm/slub.c')
-rw-r--r--mm/slub.c50
1 files changed, 45 insertions, 5 deletions
diff --git a/mm/slub.c b/mm/slub.c
index b81a4bba1b73..5f3e34923065 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -829,6 +829,17 @@ static inline void set_orig_size(struct kmem_cache *s,
if (!slub_debug_orig_size(s))
return;
+#ifdef CONFIG_KASAN_GENERIC
+ /*
+ * KASAN could save its free meta data in object's data area at
+ * offset 0, if the size is larger than 'orig_size', it will
+ * overlap the data redzone in [orig_size+1, object_size], and
+ * the check should be skipped.
+ */
+ if (kasan_metadata_size(s, true) > orig_size)
+ orig_size = s->object_size;
+#endif
+
p += get_info_end(s);
p += sizeof(struct track) * 2;
@@ -848,6 +859,11 @@ static inline unsigned int get_orig_size(struct kmem_cache *s, void *object)
return *(unsigned int *)p;
}
+void skip_orig_size_check(struct kmem_cache *s, const void *object)
+{
+ set_orig_size(s, (void *)object, s->object_size);
+}
+
static void slab_bug(struct kmem_cache *s, char *fmt, ...)
{
struct va_format vaf;
@@ -966,17 +982,28 @@ static __printf(3, 4) void slab_err(struct kmem_cache *s, struct slab *slab,
static void init_object(struct kmem_cache *s, void *object, u8 val)
{
u8 *p = kasan_reset_tag(object);
+ unsigned int poison_size = s->object_size;
- if (s->flags & SLAB_RED_ZONE)
+ if (s->flags & SLAB_RED_ZONE) {
memset(p - s->red_left_pad, val, s->red_left_pad);
+ if (slub_debug_orig_size(s) && val == SLUB_RED_ACTIVE) {
+ /*
+ * Redzone the extra allocated space by kmalloc than
+ * requested, and the poison size will be limited to
+ * the original request size accordingly.
+ */
+ poison_size = get_orig_size(s, object);
+ }
+ }
+
if (s->flags & __OBJECT_POISON) {
- memset(p, POISON_FREE, s->object_size - 1);
- p[s->object_size - 1] = POISON_END;
+ memset(p, POISON_FREE, poison_size - 1);
+ p[poison_size - 1] = POISON_END;
}
if (s->flags & SLAB_RED_ZONE)
- memset(p + s->object_size, val, s->inuse - s->object_size);
+ memset(p + poison_size, val, s->inuse - poison_size);
}
static void restore_bytes(struct kmem_cache *s, char *message, u8 data,
@@ -1120,6 +1147,7 @@ static int check_object(struct kmem_cache *s, struct slab *slab,
{
u8 *p = object;
u8 *endobject = object + s->object_size;
+ unsigned int orig_size;
if (s->flags & SLAB_RED_ZONE) {
if (!check_bytes_and_report(s, slab, object, "Left Redzone",
@@ -1129,6 +1157,17 @@ static int check_object(struct kmem_cache *s, struct slab *slab,
if (!check_bytes_and_report(s, slab, object, "Right Redzone",
endobject, val, s->inuse - s->object_size))
return 0;
+
+ if (slub_debug_orig_size(s) && val == SLUB_RED_ACTIVE) {
+ orig_size = get_orig_size(s, object);
+
+ if (s->object_size > orig_size &&
+ !check_bytes_and_report(s, slab, object,
+ "kmalloc Redzone", p + orig_size,
+ val, s->object_size - orig_size)) {
+ return 0;
+ }
+ }
} else {
if ((s->flags & SLAB_POISON) && s->object_size < s->inuse) {
check_bytes_and_report(s, slab, p, "Alignment padding",
@@ -4206,7 +4245,8 @@ static int calculate_sizes(struct kmem_cache *s)
*/
s->inuse = size;
- if ((flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) ||
+ if (slub_debug_orig_size(s) ||
+ (flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) ||
((flags & SLAB_RED_ZONE) && s->object_size < sizeof(void *)) ||
s->ctor) {
/*