[patch 5/9] mm, slab: initialize object alignment on cache creation

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From: David Rientjes <rientjes@xxxxxxxxxx>
Subject: mm, slab: initialize object alignment on cache creation

Since 4590685546a3 ("mm/sl[aou]b: Common alignment code"), the "ralign"
automatic variable in __kmem_cache_create() may be used as uninitialized.

The proper alignment defaults to BYTES_PER_WORD and can be overridden by
SLAB_RED_ZONE or the alignment specified by the caller.

This fixes https://bugzilla.kernel.org/show_bug.cgi?id=85031

Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
Reported-by: Andrei Elovikov <a.elovikov@xxxxxxxxx>
Acked-by: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/slab.c |   11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff -puN mm/slab.c~mm-slab-initialize-object-alignment-on-cache-creation mm/slab.c
--- a/mm/slab.c~mm-slab-initialize-object-alignment-on-cache-creation
+++ a/mm/slab.c
@@ -2124,7 +2124,8 @@ static int __init_refok setup_cpu_cache(
 int
 __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
 {
-	size_t left_over, freelist_size, ralign;
+	size_t left_over, freelist_size;
+	size_t ralign = BYTES_PER_WORD;
 	gfp_t gfp;
 	int err;
 	size_t size = cachep->size;
@@ -2157,14 +2158,6 @@ __kmem_cache_create (struct kmem_cache *
 		size &= ~(BYTES_PER_WORD - 1);
 	}
 
-	/*
-	 * Redzoning and user store require word alignment or possibly larger.
-	 * Note this will be overridden by architecture or caller mandated
-	 * alignment if either is greater than BYTES_PER_WORD.
-	 */
-	if (flags & SLAB_STORE_USER)
-		ralign = BYTES_PER_WORD;
-
 	if (flags & SLAB_RED_ZONE) {
 		ralign = REDZONE_ALIGN;
 		/* If redzoning, ensure that the second redzone is suitably
_
--
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