Patch "bcache: prevent crash on changing writeback_running" has been added to the 3.14-stable tree

Patch "bcache: prevent crash on changing writeback_running" has been added to the 3.14-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    bcache: prevent crash on changing writeback_running

to the 3.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     bcache-prevent-crash-on-changing-writeback_running.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 8d16ce540c94c9d366eb36fc91b7154d92d6397b Mon Sep 17 00:00:00 2001
From: Stefan Bader <stefan.bader@canonical.com>
Date: Sun, 29 Nov 2015 18:44:49 -0800
Subject: bcache: prevent crash on changing writeback_running

From: Stefan Bader <stefan.bader@canonical.com>

commit 8d16ce540c94c9d366eb36fc91b7154d92d6397b upstream.

Added a safeguard in the shutdown case. At least while not being
attached it is also possible to trigger a kernel bug by writing into
writeback_running. This change  adds the same check before trying to
wake up the thread for that case.

Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/md/bcache/writeback.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/md/bcache/writeback.h
+++ b/drivers/md/bcache/writeback.h
@@ -63,7 +63,8 @@ static inline bool should_writeback(stru
 
 static inline void bch_writeback_queue(struct cached_dev *dc)
 {
-	wake_up_process(dc->writeback_thread);
+	if (!IS_ERR_OR_NULL(dc->writeback_thread))
+		wake_up_process(dc->writeback_thread);
 }
 
 static inline void bch_writeback_add(struct cached_dev *dc)


Patches currently in stable-queue which might be from stefan.bader@canonical.com are

queue-3.14/bcache-prevent-crash-on-changing-writeback_running.patch