linux-kernel - [PATCH 6/8] xfs: fix unsigned underflow

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Date:	Thu, 15 Jul 2010 22:46:45 +0400
From:	Kulikov Vasiliy <segooon@...il.com>
To:	kernel-janitors@...r.kernel.org
Cc:	Alex Elder <aelder@....com>, xfs-masters@....sgi.com,
	Christoph Hellwig <hch@....de>,
	Dave Chinner <dchinner@...hat.com>,
	Felix Blyakher <felixb@....com>, xfs@....sgi.com,
	linux-kernel@...r.kernel.org
Subject: [PATCH 6/8] xfs: fix unsigned underflow

map_len is unsigned. Checking map_len <= 0 is buggy when it should be
below zero. So, check exact expression instead of map_len.

Signed-off-by: Kulikov Vasiliy <segooon@...il.com>
---
 fs/xfs/xfs_vnodeops.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_vnodeops.c b/fs/xfs/xfs_vnodeops.c
index 65e0879..66d585c 100644
--- a/fs/xfs/xfs_vnodeops.c
+++ b/fs/xfs/xfs_vnodeops.c
@@ -591,9 +591,9 @@ xfs_free_eofblocks(
 	 */
 	end_fsb = XFS_B_TO_FSB(mp, ((xfs_ufsize_t)ip->i_size));
 	last_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)XFS_MAXIOFFSET(mp));
-	map_len = last_fsb - end_fsb;
-	if (map_len <= 0)
+	if (last_fsb <= end_fsb)
 		return 0;
+	map_len = last_fsb - end_fsb;
 
 	nimaps = 1;
 	xfs_ilock(ip, XFS_ILOCK_SHARED);
-- 
1.7.0.4

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