[3.11.y.z extended stable] Patch "ext4: fix del_timer() misuse for ->s_err_report" 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: fix del_timer() misuse for ->s_err_report

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

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

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 8b299b9d25954ac2cb611a75fd20f85edd168bb2 Mon Sep 17 00:00:00 2001
From: Al Viro <viro at ZenIV.linux.org.uk>
Date: Sun, 8 Dec 2013 20:52:31 -0500
Subject: ext4: fix del_timer() misuse for ->s_err_report

commit 9105bb149bbbc555d2e11ba5166dfe7a24eae09e upstream.

That thing should be del_timer_sync(); consider what happens
if ext4_put_super() call of del_timer() happens to come just as it's
getting run on another CPU.  Since that timer reschedules itself
to run next day, you are pretty much guaranteed that you'll end up
with kfree'd scheduled timer, with usual fun consequences.  AFAICS,
that's -stable fodder all way back to 2010... [the second del_timer_sync()
is almost certainly not needed, but it doesn't hurt either]

Signed-off-by: Al Viro <viro at zeniv.linux.org.uk>
Signed-off-by: "Theodore Ts'o" <tytso at mit.edu>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/ext4/super.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index b59373b..e222177 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -775,7 +775,7 @@ static void ext4_put_super(struct super_block *sb)
 	}

 	ext4_es_unregister_shrinker(sbi);
-	del_timer(&sbi->s_err_report);
+	del_timer_sync(&sbi->s_err_report);
 	ext4_release_system_zone(sb);
 	ext4_mb_release(sb);
 	ext4_ext_release(sb);
@@ -4124,7 +4124,7 @@ failed_mount_wq:
 	}
 failed_mount3:
 	ext4_es_unregister_shrinker(sbi);
-	del_timer(&sbi->s_err_report);
+	del_timer_sync(&sbi->s_err_report);
 	if (sbi->s_flex_groups)
 		ext4_kvfree(sbi->s_flex_groups);
 	percpu_counter_destroy(&sbi->s_freeclusters_counter);
--
1.8.3.2