mm/slub.c: fix wrong address during slab padding restoration

Start address calculated for slab padding restoration was wrong.  Wrong
address would point to some section before padding and could cause
corruption

Link: http://lkml.kernel.org/r/1516604578-4577-1-git-send-email-balasubramani_vivekanandan@mentor.com
Signed-off-by: Balasubramani Vivekanandan <balasubramani_vivekanandan@mentor.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/slub.c b/mm/slub.c
index cfd56e5a35fb9790ac6426dd62abb9964f1ce72b..733ba32c031b9b610a87351405bdaa952885f1a4 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -838,6 +838,7 @@ static int slab_pad_check(struct kmem_cache *s, struct page *page)
        u8 *start;
        u8 *fault;
        u8 *end;
+       u8 *pad;
        int length;
        int remainder;
 
@@ -851,8 +852,9 @@ static int slab_pad_check(struct kmem_cache *s, struct page *page)
        if (!remainder)
                return 1;
 
+       pad = end - remainder;
        metadata_access_enable();
-       fault = memchr_inv(end - remainder, POISON_INUSE, remainder);
+       fault = memchr_inv(pad, POISON_INUSE, remainder);
        metadata_access_disable();
        if (!fault)
                return 1;
@@ -860,9 +862,9 @@ static int slab_pad_check(struct kmem_cache *s, struct page *page)
                end--;
 
        slab_err(s, page, "Padding overwritten. 0x%p-0x%p", fault, end - 1);
-       print_section(KERN_ERR, "Padding ", end - remainder, remainder);
+       print_section(KERN_ERR, "Padding ", pad, remainder);
 
-       restore_bytes(s, "slab padding", POISON_INUSE, end - remainder, end);
+       restore_bytes(s, "slab padding", POISON_INUSE, fault, end);
        return 0;
 }