linux-ext4 - [PATCH 5/5] ext4: Fix extent merging in ext4_ext_shift_path

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1397673182-5326-5-git-send-email-lczerner@redhat.com>
Date:	Wed, 16 Apr 2014 20:33:02 +0200
From:	Lukas Czerner <lczerner@...hat.com>
To:	linux-ext4@...r.kernel.org
Cc:	linkinjeon@...il.com, Lukas Czerner <lczerner@...hat.com>
Subject: [PATCH 5/5] ext4: Fix extent merging in ext4_ext_shift_path_extents()

There is a bug in ext4_ext_shift_path_extents() where if we actually
manage to merge a extent we would skip shifting the next extent. This
will result in in one extent in the extent tree not being properly
shifted.

This is causing failure in various xfstests tests using fsx or fsstress
with collapse range support. It will also cause file system corruption
which looks something like:

 e2fsck 1.42.9 (4-Feb-2014)
 Pass 1: Checking inodes, blocks, and sizes
 Inode 20 has out of order extents
        (invalid logical block 3, physical block 492938, len 2)
 Clear? yes
 ...

when running e2fsck.

It's also very easily reproducible just by running fsx without any
parameters. I can usually hit the problem within a minute.

Fix it by increasing ex_start only if we're not merging the extent.

Signed-off-by: Lukas Czerner <lczerner@...hat.com>
---
 fs/ext4/extents.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 84bb668..5fa31cb 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -5230,13 +5230,14 @@ ext4_ext_shift_path_extents(struct ext4_ext_path *path, ext4_lblk_t shift,
 
 			while (ex_start <= ex_last) {
 				ex_start->ee_block -= shift;
-				if (ex_start >
-					EXT_FIRST_EXTENT(path[depth].p_hdr)) {
-					if (ext4_ext_try_to_merge_right(inode,
-						path, ex_start - 1))
-						ex_last--;
-				}
-				ex_start++;
+				/* Try to merge to the left. */
+				if ((ex_start >
+				     EXT_FIRST_EXTENT(path[depth].p_hdr)) &&
+				    ext4_ext_try_to_merge_right(inode,
+							path, ex_start - 1))
+					ex_last--;
+				else
+					ex_start++;
 			}
 			err = ext4_ext_dirty(handle, inode, path + depth);
 			if (err)
-- 
1.8.3.1

--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html