w1: fix oops when w1_search is called from netlink connector

On Sat, Mar 02, 2013 at 10:45:10AM +0100, Sven Geggus wrote:
> This is the bad commit I found doing git bisect:
> 04f482f is the first bad commit
> commit 04f482f
> Author: Patrick McHardy <[email protected]>
> 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 <[email protected]>
Acked-by: Evgeniy Polyakov <[email protected]>
Cc: Josh Boyer <[email protected]>
Tested-by: Sven Geggus <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Cc: stable <[email protected]> # 3.0+

drivers/w1/w1.c

@@ -931,7 +931,8 @@ void w1_search(struct w1_master *dev, u8 search_type, w1_slave_found_callback cb
 			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()) {
 				mutex_unlock(&dev->bus_mutex);
 				dev_dbg(&dev->dev, "Abort w1_search\n");
 				return;