On Fri, 8 Jun 2012, Ming Lei wrote: > Firstly, .shutdown callback may touch a uninitialized hardware > if dev->driver is set and .probe is not completed. > > Secondly, device_shutdown() may dereference a null pointer to cause > oops when dev->driver is cleared after it is checked in > device_shutdown(). > > So just hold device lock and its parent lock if it has to fix the > races. > > Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx> > --- > drivers/base/core.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/base/core.c b/drivers/base/core.c > index 346be8b..cbc8bd2 100644 > --- a/drivers/base/core.c > +++ b/drivers/base/core.c > @@ -1820,6 +1820,11 @@ void device_shutdown(void) > list_del_init(&dev->kobj.entry); > spin_unlock(&devices_kset->list_lock); > > + /*hold lock[s] to avoid races with .probe/.release*/ > + if (dev->parent) > + device_lock(dev->parent); > + device_lock(dev); Would you prefer to use device_trylock in a loop? I guess this comes down to which you prefer: a hang during shutdown, or a crash. :-) Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
