From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761991Ab2FVKCb (ORCPT ); Fri, 22 Jun 2012 06:02:31 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:39022 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761964Ab2FVKCa (ORCPT ); Fri, 22 Jun 2012 06:02:30 -0400 From: Ming Lei To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, Ming Lei , Alan Stern Subject: [PATCH] driver core: fix shutdown races with probe/remove(v3) Date: Fri, 22 Jun 2012 18:01:40 +0800 Message-Id: <1340359301-7468-1-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 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 has been checked in device_shutdown(). So just hold device lock and its parent lock(if it has) to fix the races. Cc: Alan Stern Signed-off-by: Ming Lei --- v3: - add comments on holding parent's reference count - acquire device lock directly instead of using device_trylock as required by Greg 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 | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/drivers/base/core.c b/drivers/base/core.c index 846d12b..65849a9 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -1812,6 +1812,13 @@ void device_shutdown(void) while (!list_empty(&devices_kset->list)) { dev = list_entry(devices_kset->list.prev, struct device, kobj.entry); + + /* + * hold reference count of device's parent to + * prevent it from being freed because parent's + * lock is to be held + */ + get_device(dev->parent); get_device(dev); /* * Make sure the device is off the kset list, in the @@ -1820,6 +1827,11 @@ 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) + device_lock(dev->parent); + device_lock(dev); + /* Don't allow any more runtime suspends */ pm_runtime_get_noresume(dev); pm_runtime_barrier(dev); @@ -1831,7 +1843,13 @@ void device_shutdown(void) dev_dbg(dev, "shutdown\n"); dev->driver->shutdown(dev); } + + device_unlock(dev); + if (dev->parent) + device_unlock(dev->parent); + put_device(dev); + put_device(dev->parent); spin_lock(&devices_kset->list_lock); } -- 1.7.9.5