Patch "driver core: platform: fix race condition with driver_override" has been added to the 4.4-stable tree

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

driver core: platform: fix race condition with driver_override

to the 4.4-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:
driver-core-platform-fix-race-condition-with-driver_override.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Adrian Salido <[email protected]>
Date: Tue, 25 Apr 2017 16:55:26 -0700
Subject: driver core: platform: fix race condition with driver_override

From: Adrian Salido <[email protected]>

commit 6265539776a0810b7ce6398c27866ddb9c6bd154 upstream.

The driver_override implementation is susceptible to race condition when different threads are reading vs storing a different driver override. Add locking to avoid race condition.

---
 drivers/base/platform.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

@@ -807,7 +807,7 @@ static ssize_t driver_override_store(str
 				     const char *buf, size_t count)
 {
 	struct platform_device *pdev = to_platform_device(dev);
-	char *driver_override, *old = pdev->driver_override, *cp;
+	char *driver_override, *old, *cp;
 
 	if (count > PATH_MAX)
 		return -EINVAL;

@@ -820,12 +820,15 @@ static ssize_t driver_override_store(str
 	if (cp)
 		*cp = '\0';
 
+	device_lock(dev);
+	old = pdev->driver_override;
 	if (strlen(driver_override)) {
 		pdev->driver_override = driver_override;
 	} else {
 		kfree(driver_override);
 		pdev->driver_override = NULL;
 	}
+	device_unlock(dev);
 
 	kfree(old);
 

@@ -836,8 +839,12 @@ static ssize_t driver_override_show(stru
 				    struct device_attribute *attr, char *buf)
 {
 	struct platform_device *pdev = to_platform_device(dev);
+	ssize_t len;
 
-	return sprintf(buf, "%s\n", pdev->driver_override);
+	device_lock(dev);
+	len = sprintf(buf, "%s\n", pdev->driver_override);
+	device_unlock(dev);
+	return len;
 }
 static DEVICE_ATTR_RW(driver_override);
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/driver-core-platform-fix-race-condition-with-driver_override.patch