linux-kernel - [47/91] slab: fix object alignment

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20100824224216.107007664@clark.site>
Date:	Tue, 24 Aug 2010 15:42:09 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Christoph Lameter <cl@...ux.com>,
	Carsten Otte <cotte@...ibm.com>,
	Pekka Enberg <penberg@...nel.org>
Subject: [47/91] slab: fix object alignment

2.6.34-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Carsten Otte <cotte@...ibm.com>

commit 1ab335d8f85792e3b107ff8237d53cf64db714df upstream.

This patch fixes alignment of slab objects in case CONFIG_DEBUG_PAGEALLOC is
active.
Before this spot in kmem_cache_create, we have this situation:
- align contains the required alignment of the object
- cachep->obj_offset is 0 or equals align in case of CONFIG_DEBUG_SLAB
- size equals the size of the object, or object plus trailing redzone in case
  of CONFIG_DEBUG_SLAB

This spot tries to fill one page per object if the object is in certain size
limits, however setting obj_offset to PAGE_SIZE - size does break the object
alignment since size may not be aligned with the required alignment.
This patch simply adds an ALIGN(size, align) to the equation and fixes the
object size detection accordingly.

This code in drivers/s390/cio/qdio_setup_init has lead to incorrectly aligned
slab objects (sizeof(struct qdio_q) equals 1792):
	qdio_q_cache = kmem_cache_create("qdio_q", sizeof(struct qdio_q),
					 256, 0, NULL);

Acked-by: Christoph Lameter <cl@...ux.com>
Signed-off-by: Carsten Otte <cotte@...ibm.com>
Signed-off-by: Pekka Enberg <penberg@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 mm/slab.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2262,8 +2262,8 @@ kmem_cache_create (const char *name, siz
 	}
 #if FORCED_DEBUG && defined(CONFIG_DEBUG_PAGEALLOC)
 	if (size >= malloc_sizes[INDEX_L3 + 1].cs_size
-	    && cachep->obj_size > cache_line_size() && size < PAGE_SIZE) {
-		cachep->obj_offset += PAGE_SIZE - size;
+	    && cachep->obj_size > cache_line_size() && ALIGN(size, align) < PAGE_SIZE) {
+		cachep->obj_offset += PAGE_SIZE - ALIGN(size, align);
 		size = PAGE_SIZE;
 	}
 #endif


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/