linux-kernel - [ 02/42] ext4: Avoid underflow in ext4_trim

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Date:	Thu, 25 Oct 2012 17:05:10 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	alan@...rguk.ukuu.org.uk, Lukas Czerner <lczerner@...hat.com>,
	"Theodore Tso" <tytso@....edu>
Subject: [ 02/42] ext4: Avoid underflow in ext4_trim_fs()

3.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Lukas Czerner <lczerner@...hat.com>

commit 5de35e8d5c02d271c20e18337e01bc20e6ef472e upstream.

Currently if len argument in ext4_trim_fs() is smaller than one block,
the 'end' variable underflow. Avoid that by returning EINVAL if len is
smaller than file system block.

Also remove useless unlikely().

Signed-off-by: Lukas Czerner <lczerner@...hat.com>
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/ext4/mballoc.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4984,8 +4984,9 @@ int ext4_trim_fs(struct super_block *sb,
 	end = start + (range->len >> sb->s_blocksize_bits) - 1;
 	minlen = range->minlen >> sb->s_blocksize_bits;
 
-	if (unlikely(minlen > EXT4_CLUSTERS_PER_GROUP(sb)) ||
-	    unlikely(start >= max_blks))
+	if (minlen > EXT4_CLUSTERS_PER_GROUP(sb) ||
+	    start >= max_blks ||
+	    range->len < sb->s_blocksize)
 		return -EINVAL;
 	if (end >= max_blks)
 		end = max_blks - 1;


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