ext4: check for zero length extent explicitly

[ Upstream commit 2f974865ffdfe7b9f46a9940836c8b167342563d ]

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>
Cc: stable@vger.kernel.org
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 6cfacbb0f92854fef58385849123fa60ee229488..b5fcb1ac0dd71dcd06ca6ad8960d7f98eb9cc08e 100644 (file)
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -377,7 +377,7 @@ 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);
 }