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:
> 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>
Cc: stable <stable@vger.kernel.org> # 3.0+

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c
index 7994d933f040..7ce277d2bb67 100644
--- a/drivers/w1/w1.c
+++ b/drivers/w1/w1.c
@@ -924,7 +924,8 @@ 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;