Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752812Ab2FKFOi (ORCPT ); Mon, 11 Jun 2012 01:14:38 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:48027 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751964Ab2FKFOg (ORCPT ); Mon, 11 Jun 2012 01:14:36 -0400 From: Ming Lei To: Greg Kroah-Hartman Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Ming Lei , Alan Stern , stable@vger.kernel.org Subject: [PATCH] driver core: fix shutdown races with probe/remove(v2) Date: Mon, 11 Jun 2012 13:13:20 +0800 Message-Id: <1339391600-17815-1-git-send-email-ming.lei@canonical.com> X-Mailer: git-send-email 1.7.9.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2638 Lines: 97 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 Cc: stable@vger.kernel.org Signed-off-by: Ming Lei --- 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 linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/