[ 21/48] w1: fix oops when w1_search is called from netlink connector

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Marcin Jurkowski <marcin1j@gmail.com>

commit 9d1817cab2f030f6af360e961cc69bb1da8ad765 upstream.

On Sat, Mar 02, 2013 at 10:45:10AM +0100, Sven Geggus wrote:
> This is the bad commit I found doing git bisect:
> 04f482faf50535229a5a5c8d629cf963899f857c is the first bad commit
> commit 04f482faf50535229a5a5c8d629cf963899f857c
> Author: Patrick McHardy <kaber@trash.net>
> Date:   Mon Mar 28 08:39:36 2011 +0000

Good job. I was too lazy to bisect for bad commit;)

Reading the code I found problematic kthread_should_stop call from netlink
connector which causes the oops. After applying a patch, I've been testing
owfs+w1 setup for nearly two days and it seems to work very reliable (no
hangs, no memleaks etc).
More detailed description and possible fix is given below:

Function w1_search can be called from either kthread or netlink callback.
While the former works fine, the latter causes oops due to kthread_should_stop
invocation.

This patch adds a check if w1_search is serving netlink command, skipping
kthread_should_stop invocation if so.

Signed-off-by: Marcin Jurkowski <marcin1j@gmail.com>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Josh Boyer <jwboyer@gmail.com>
Tested-by: Sven Geggus <lists@fuchsschwanzdomain.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/w1/w1.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/w1/w1.c
+++ b/drivers/w1/w1.c
@@ -928,7 +928,8 @@ void w1_search(struct w1_master *dev, u8
 			tmp64 = (triplet_ret >> 2);
 			rn |= (tmp64 << i);
 
-			if (kthread_should_stop()) {
+			/* ensure we're called from kthread and not by netlink callback */
+			if (!dev->priv && kthread_should_stop()) {
 				dev_dbg(&dev->dev, "Abort w1_search\n");
 				return;
 			}