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authorKees Cook <keescook@chromium.org>2021-06-15 18:23:22 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-06-16 09:24:42 -0700
commit74c1d3e081533825f2611e46edea1fcdc0701985 (patch)
treea958636460f1040d74dae489252612a445120547 /mm/slab_common.c
parent8669dbab2ae56085c128894b181c2aa50f97e368 (diff)
mm/slub: fix redzoning for small allocations
The redzone area for SLUB exists between s->object_size and s->inuse (which is at least the word-aligned object_size). If a cache were created with an object_size smaller than sizeof(void *), the in-object stored freelist pointer would overwrite the redzone (e.g. with boot param "slub_debug=ZF"): BUG test (Tainted: G B ): Right Redzone overwritten ----------------------------------------------------------------------------- INFO: 0xffff957ead1c05de-0xffff957ead1c05df @offset=1502. First byte 0x1a instead of 0xbb INFO: Slab 0xffffef3950b47000 objects=170 used=170 fp=0x0000000000000000 flags=0x8000000000000200 INFO: Object 0xffff957ead1c05d8 @offset=1496 fp=0xffff957ead1c0620 Redzone (____ptrval____): bb bb bb bb bb bb bb bb ........ Object (____ptrval____): f6 f4 a5 40 1d e8 ...@.. Redzone (____ptrval____): 1a aa .. Padding (____ptrval____): 00 00 00 00 00 00 00 00 ........ Store the freelist pointer out of line when object_size is smaller than sizeof(void *) and redzoning is enabled. Additionally remove the "smaller than sizeof(void *)" check under CONFIG_DEBUG_VM in kmem_cache_sanity_check() as it is now redundant: SLAB and SLOB both handle small sizes. (Note that no caches within this size range are known to exist in the kernel currently.) Link: https://lkml.kernel.org/r/20210608183955.280836-3-keescook@chromium.org Fixes: 81819f0fc828 ("SLUB core") Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: "Lin, Zhenpeng" <zplin@psu.edu> Cc: Marco Elver <elver@google.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Roman Gushchin <guro@fb.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slab_common.c')
-rw-r--r--mm/slab_common.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/mm/slab_common.c b/mm/slab_common.c
index a4a571428c51..7cab77655f11 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -97,8 +97,7 @@ EXPORT_SYMBOL(kmem_cache_size);
#ifdef CONFIG_DEBUG_VM
static int kmem_cache_sanity_check(const char *name, unsigned int size)
{
- if (!name || in_interrupt() || size < sizeof(void *) ||
- size > KMALLOC_MAX_SIZE) {
+ if (!name || in_interrupt() || size > KMALLOC_MAX_SIZE) {
pr_err("kmem_cache_create(%s) integrity check failed\n", name);
return -EINVAL;
}