[PATCH 3.14 39/64] ext4: check for zero length extent explicitly

Greg Kroah-Hartman
2015-06-03T12:13:20Z

From: Eryu Guan <guaneryu@gmail.com>

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>

---
fs/ext4/extents.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -361,7 +361,7 @@ static int ext4_valid_extent(struct inod
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);
}