[3.16.y-ckt stable] Patch "ext4: check for zero length extent explicitly" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    ext4: check for zero length extent explicitly

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt13.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 30d8953ff1eeef91bb499decb7487087cffe2060 Mon Sep 17 00:00:00 2001
From: Eryu Guan <guaneryu at gmail.com>
Date: Thu, 14 May 2015 19:00:45 -0400
Subject: 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 at gmail.com>
Signed-off-by: Theodore Ts'o <tytso at mit.edu>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/ext4/extents.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 99d74306e770..a2c5bb7e71bb 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -361,7 +361,7 @@ 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);
 }