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 try to hold device lock and its parent lock(if it has) to fix the races. Cc: Alan Stern <[email protected]> Cc: [email protected] Signed-off-by: Ming Lei <[email protected]> --- v2: - take Alan's suggestion to use device_trylock to avoid hanging during shutdown by buggy device or driver - hold parent reference counter drivers/base/core.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/drivers/base/core.c b/drivers/base/core.c index 346be8b..f2fc989 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -1796,6 +1796,16 @@ out: } EXPORT_SYMBOL_GPL(device_move); +static int __try_lock(struct device *dev) +{ + int i = 0; + + while (!device_trylock(dev) && i++ < 100) + msleep(10); + + return i < 100; +} + /** * device_shutdown - call ->shutdown() on each device to shutdown. */ @@ -1810,8 +1820,11 @@ void device_shutdown(void) * devices offline, even as the system is shutting down. */ while (!list_empty(&devices_kset->list)) { + int nonlocked; + dev = list_entry(devices_kset->list.prev, struct device, kobj.entry); + get_device(dev->parent); get_device(dev); /* * Make sure the device is off the kset list, in the @@ -1820,6 +1833,18 @@ void device_shutdown(void) list_del_init(&dev->kobj.entry); spin_unlock(&devices_kset->list_lock); + /* hold lock to avoid race with .probe/.release */ + if (dev->parent && !__try_lock(dev->parent)) + nonlocked = 2; + else if (!__try_lock(dev)) + nonlocked = 1; + else + nonlocked = 0; + + if (nonlocked) + dev_err(dev, "can't hold %slock for shutdown\n", + nonlocked == 1 ? "" : "parent "); + /* Don't allow any more runtime suspends */ pm_runtime_get_noresume(dev); pm_runtime_barrier(dev); @@ -1831,7 +1856,14 @@ void device_shutdown(void) dev_dbg(dev, "shutdown\n"); dev->driver->shutdown(dev); } + + if (!nonlocked) + device_unlock(dev); + if (dev->parent && nonlocked != 2) + device_unlock(dev->parent); + put_device(dev); + put_device(dev->parent); spin_lock(&devices_kset->list_lock); } -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
