[062/151] Driver core: fix race in dev_driver_string

Greg KH
2009-12-17T04:33:22Z

From: Alan Stern <stern@rowland.harvard.edu>

commit 3589972e51fac1e02d0aaa576fa47f568cb94d40 upstream.

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: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/base/core.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -56,7 +56,14 @@ static inline int device_is_not_partitio
*/
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 : ""));
}