[ 03/85] ext4: Avoid underflow in ext4_trim_fs()

[Greg Kroah-Hartman]

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

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

From: Lukas Czerner <lczerner@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4987,8 +4987,9 @@ 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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