Driver core: fix race in dev_driver_string
This patch (as1310) works around a race in dev_driver_string(). If
the device is unbound while the function is running, dev->driver might
become NULL after we test it and before we dereference it.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@kernel.org>
Cc: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 353b137..f1290cb 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -56,7 +56,14 @@
*/
const char *dev_driver_string(const struct device *dev)
{
- return dev->driver ? dev->driver->name :
+ struct device_driver *drv;
+
+ /* dev->driver can change to NULL underneath us because of unbinding,
+ * so be careful about accessing it. dev->bus and dev->class should
+ * never change once they are set, so they don't need special care.
+ */
+ drv = ACCESS_ONCE(dev->driver);
+ return drv ? drv->name :
(dev->bus ? dev->bus->name :
(dev->class ? dev->class->name : ""));
}