linux-kernel - [PATCH] w1: do not unlock unheld list_mutex in __w1_remove_master

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Date:	Thu,  1 May 2014 00:37:58 +0400
From:	Alexey Khoroshilov <khoroshilov@...ras.ru>
To:	David Fries <David@...es.net>, Evgeniy Polyakov <zbr@...emap.net>
Cc:	Alexey Khoroshilov <khoroshilov@...ras.ru>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] w1: do not unlock unheld list_mutex in __w1_remove_master_device()

w1_process_callbacks() expects to be called with dev->list_mutex held,
but it is the fact only in w1_process(). __w1_remove_master_device()
calls w1_process_callbacks() after it releases list_mutex.

The patch fixes __w1_remove_master_device() to acquire list_mutex
for w1_process_callbacks(). It is implemented by moving
w1_process_callbacks() functionality to __w1_process_callbacks()
and adding a wrapper with the old name.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@...ras.ru>
---
 drivers/w1/w1.c |  8 +++++---
 drivers/w1/w1.h | 13 ++++++++++++-
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c
index ff52618cafbe..e507c51512aa 100644
--- a/drivers/w1/w1.c
+++ b/drivers/w1/w1.c
@@ -1075,12 +1075,14 @@ static void w1_search_process(struct w1_master *dev, u8 search_type)
 }
 
 /**
- * w1_process_callbacks() - execute each dev->async_list callback entry
+ * __w1_process_callbacks() - execute each dev->async_list callback entry
  * @dev: w1_master device
  *
+ * The w1 master list_mutex must be held.
+ *
  * Return: 1 if there were commands to executed 0 otherwise
  */
-int w1_process_callbacks(struct w1_master *dev)
+int __w1_process_callbacks(struct w1_master *dev)
 {
 	int ret = 0;
 	struct w1_async_cmd *async_cmd, *async_n;
@@ -1122,7 +1124,7 @@ int w1_process(void *data)
 		/* Note, w1_process_callback drops the lock while processing,
 		 * but locks it again before returning.
 		 */
-		if (!w1_process_callbacks(dev) && jremain) {
+		if (!__w1_process_callbacks(dev) && jremain) {
 			/* a wake up is either to stop the thread, process
 			 * callbacks, or search, it isn't process callbacks, so
 			 * schedule a search.
diff --git a/drivers/w1/w1.h b/drivers/w1/w1.h
index 734dab7fc687..e357321a5e13 100644
--- a/drivers/w1/w1.h
+++ b/drivers/w1/w1.h
@@ -341,9 +341,20 @@ extern int w1_max_slave_ttl;
 extern struct list_head w1_masters;
 extern struct mutex w1_mlock;
 
-extern int w1_process_callbacks(struct w1_master *dev);
+extern int __w1_process_callbacks(struct w1_master *dev);
 extern int w1_process(void *);
 
+static inline int w1_process_callbacks(struct w1_master *dev)
+{
+	int ret;
+
+	mutex_lock(&dev->list_mutex);
+	ret = __w1_process_callbacks(dev);
+	mutex_unlock(&dev->list_mutex);
+	return ret;
+}
+
+
 #endif /* __KERNEL__ */
 
 #endif /* __W1_H */
-- 
1.8.3.2

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