From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759374Ab3FCWN4 (ORCPT ); Mon, 3 Jun 2013 18:13:56 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:2298 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759088Ab3FCWMf (ORCPT ); Mon, 3 Jun 2013 18:12:35 -0400 X-Authority-Analysis: v=2.0 cv=BcJaI8R2 c=1 sm=0 a=rXTBtCOcEpjy1lPqhTCpEQ==:17 a=mNMOxpOpBa8A:10 a=Ciwy3NGCPMMA:10 a=ckvJjgcNJdAA:10 a=5SG0PmZfjMsA:10 a=bbbx4UPp9XUA:10 a=meVymXHHAAAA:8 a=KbHWfzvD86IA:10 a=_jlGtV7tAAAA:8 a=u6Kjp6XQMGfe5Rn6x1sA:9 a=L1RTw_NLzc0A:10 a=jeBq3FmKZ4MA:10 a=rXTBtCOcEpjy1lPqhTCpEQ==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 74.67.115.198 Message-Id: <20130603221159.981651136@goodmis.org> User-Agent: quilt/0.60-1 Date: Mon, 03 Jun 2013 18:11:01 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Arkadiusz Miskiewicz , Guenter Roeck , Wim Van Sebroeck Subject: [45/65] watchdog: Fix race condition in registration code References: <20130603221016.243553628@goodmis.org> Content-Disposition: inline; filename=0045-watchdog-Fix-race-condition-in-registration-code.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.6.11.5 stable review patch. If anyone has any objections, please let me know. ------------------ From: Guenter Roeck [ Upstream commit 60403f7a4d9368d187f79cba5e4672d01df37574 ] A race condition exists when registering the first watchdog device. Sequence of events: - watchdog_register_device calls watchdog_dev_register - watchdog_dev_register creates the watchdog misc device by calling misc_register. At that time, the matching character device (/dev/watchdog0) does not yet exist, and old_wdd is not set either. - Userspace gets an event and opens /dev/watchdog - watchdog_open is called and sets wdd = old_wdd, which is still NULL, and tries to dereference it. This causes the kernel to panic. Seen with systemd trying to open /dev/watchdog immediately after it was created. Reported-by: Arkadiusz Miskiewicz Signed-off-by: Guenter Roeck Tested-by: Arkadiusz Miskiewicz Signed-off-by: Wim Van Sebroeck Signed-off-by: Steven Rostedt --- drivers/watchdog/watchdog_dev.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c index ef8edec..05a5310 100644 --- a/drivers/watchdog/watchdog_dev.c +++ b/drivers/watchdog/watchdog_dev.c @@ -524,6 +524,7 @@ int watchdog_dev_register(struct watchdog_device *watchdog) int err, devno; if (watchdog->id == 0) { + old_wdd = watchdog; watchdog_miscdev.parent = watchdog->parent; err = misc_register(&watchdog_miscdev); if (err != 0) { @@ -532,9 +533,9 @@ int watchdog_dev_register(struct watchdog_device *watchdog) if (err == -EBUSY) pr_err("%s: a legacy watchdog module is probably present.\n", watchdog->info->identity); + old_wdd = NULL; return err; } - old_wdd = watchdog; } /* Fill in the data structures */ -- 1.7.10.4