ext4: check for zero length extent explicitly

commit 2f974865ffdfe7b9f46a9940836c8b167342563d upstream.

The following commit introduced a bug when checking for zero length extent

5946d08 ext4: check for overlapping extents in ext4_valid_extent_entries()

Zero length extent could pass the check if lblock is zero.

Adding the explicit check for zero length back.

Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 7fbd1c5b74afee34170e614031138f1d2df39c85..df633bb25909a354c5627bc5a5e51a90bf2fddb4 100644 (file)
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -363,7 +363,7 @@ static int ext4_valid_extent(struct inode *inode, struct ext4_extent *ext)
        ext4_lblk_t lblock = le32_to_cpu(ext->ee_block);
        ext4_lblk_t last = lblock + len - 1;
 
-       if (lblock > last)
+       if (len == 0 || lblock > last)
                return 0;
        return ext4_data_block_valid(EXT4_SB(inode->i_sb), block, len);
 }