PSA: Linux File System Corruption Bug

[alpenwasser]

I'm subscribed to the Arch Linux mailing list and just got this message in my inbox:

 

Recent Linux kernels (4.0.2+, LTS 3.14.41+), pushed to the [core] repository in

the past couple of weeks, were affected by a bug that can cause data corruption

on file systems mounted with the `discard` option and residing on software RAID

0 arrays.

The issue has been addressed in the `linux 4.0.4-2` and `linux-lts 3.14.43-2`

updates. Due to the nature of the bug, however, it is likely that data

corruption has already occurred on systems running the aforementioned kernels.

It is strongly advised to verify the integrity of affected file systems using

`fsck` and/or restore their data from known good backups.

For further information please read the [LKML post][1] by Holger Kiehl, the

[related article][2] on Phoronix, as well as the [proposed fix][3] that was

backported to the Arch kernels.

[1]: https://lkml.org/lkml/2015/5/21/167

[2]: http://www.phoronix.com/scan.php?page=news_item&px=Linux-4-EXT4-RAID-

Issue-Found

[3]: http://git.neil.brown.name/?p=md.git;a=commitdiff;h=a81157768a00e8cf8a7b

43b5ea5cac931262374f

URL: https://www.archlinux.org/news/data-corruption-on-software-raid-0-when-discard-is-used/

Debian bug report: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=785672

Arch forum discussion: https://bbs.archlinux.org/viewtopic.php?id=197400

According to the discussion on Phoronix it's also possible that this bug could

affect you if you're not running a bleeding-edge kernel if it's been backported

to an older kernel. Apparently there were Ubuntu kernels which had the bad patch

pipelined for being pushed into production (though that doesn't seem to have

happened in the end as the bug got caught before that).

http://www.phoronix.com/forums/forum/phoronix/latest-phoronix-articles/801529-the-linux-4-0-ext4-raid-corruption-bug-has-been-uncovered?p=801567#post801567

If you're among those of us who run bleeding-edge kernels you have probably already

been notified of this, but since it's pretty important I thought it appropriate

to make this post.