From: Xi Wang <xi.wang@gmail.com>
Date: Thu, 16 Feb 2012 16:56:29 +0000 (-0500)
Subject: ceph: fix overflow check in build_snap_context()
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=80834312a4da1405a9bc788313c67643de6fcb4c;p=openwrt%2Fstaging%2Fblogic.git

ceph: fix overflow check in build_snap_context()

The overflow check for a + n * b should be (n > (ULONG_MAX - a) / b),
rather than (n > ULONG_MAX / b - a).

Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Sage Weil <sage@newdream.net>
---

diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index a559c80f127a..f04c0961f993 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -331,7 +331,7 @@ static int build_snap_context(struct ceph_snap_realm *realm)
 
 	/* alloc new snap context */
 	err = -ENOMEM;
-	if (num > ULONG_MAX / sizeof(u64) - sizeof(*snapc))
+	if (num > (ULONG_MAX - sizeof(*snapc)) / sizeof(u64))
 		goto fail;
 	snapc = kzalloc(sizeof(*snapc) + num*sizeof(u64), GFP_NOFS);
 	if (!snapc)