From patchwork Mon Aug 31 20:40:29 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Felipe Balbi X-Patchwork-Id: 7101461 Return-Path: X-Original-To: patchwork-linux-omap@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 749BF9F36E for ; Mon, 31 Aug 2015 20:40:41 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 96D7620395 for ; Mon, 31 Aug 2015 20:40:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D262D206A0 for ; Mon, 31 Aug 2015 20:40:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752724AbbHaUki (ORCPT ); Mon, 31 Aug 2015 16:40:38 -0400 Received: from comal.ext.ti.com ([198.47.26.152]:54137 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752064AbbHaUkh (ORCPT ); Mon, 31 Aug 2015 16:40:37 -0400 Received: from dflxv15.itg.ti.com ([128.247.5.124]) by comal.ext.ti.com (8.13.7/8.13.7) with ESMTP id t7VKeWTF027552; Mon, 31 Aug 2015 15:40:32 -0500 Received: from DLEE70.ent.ti.com (dlemailx.itg.ti.com [157.170.170.113]) by dflxv15.itg.ti.com (8.14.3/8.13.8) with ESMTP id t7VKeW01014063; Mon, 31 Aug 2015 15:40:32 -0500 Received: from dlep33.itg.ti.com (157.170.170.75) by DLEE70.ent.ti.com (157.170.170.113) with Microsoft SMTP Server id 14.3.224.2; Mon, 31 Aug 2015 15:40:31 -0500 Received: from localhost (ileax41-snat.itg.ti.com [10.172.224.153]) by dlep33.itg.ti.com (8.14.3/8.13.8) with ESMTP id t7VKeVKn012814; Mon, 31 Aug 2015 15:40:31 -0500 From: Felipe Balbi To: James Morris CC: , , , Linux OMAP Mailing List , Felipe Balbi Subject: [PATCH] security: device_cgroup: fix RCU lockdep splat Date: Mon, 31 Aug 2015 15:40:29 -0500 Message-ID: <1441053629-31844-1-git-send-email-balbi@ti.com> X-Mailer: git-send-email 2.5.0 MIME-Version: 1.0 Sender: linux-omap-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-omap@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP while booting AM437x device, the following splat triggered: [ 12.005238] =============================== [ 12.009749] [ INFO: suspicious RCU usage. ] [ 12.014116] 4.2.0-next-20150831 #1154 Not tainted [ 12.019050] ------------------------------- [ 12.023408] security/device_cgroup.c:405 device_cgroup:verify_new_ex called without proper synchronization! [ 12.033576] other info that might help us debug this: [ 12.041942] rcu_scheduler_active = 1, debug_locks = 0 [ 12.048796] 4 locks held by systemd/1: [ 12.052700] #0: (sb_writers#7){.+.+.+}, at: [] __sb_start_write+0x8c/0xb0 [ 12.060954] #1: (&of->mutex){+.+.+.}, at: [] kernfs_fop_write+0x50/0x1b8 [ 12.069085] #2: (s_active#30){++++.+}, at: [] kernfs_fop_write+0x58/0x1b8 [ 12.077310] #3: (devcgroup_mutex){+.+...}, at: [] devcgroup_access_write+0x20/0x658 [ 12.086575] stack backtrace: [ 12.091124] CPU: 0 PID: 1 Comm: systemd Not tainted 4.2.0-next-20150831 #1154 [ 12.098609] Hardware name: Generic AM43 (Flattened Device Tree) [ 12.104807] [] (unwind_backtrace) from [] (show_stack+0x10/0x14) [ 12.112924] [] (show_stack) from [] (dump_stack+0x84/0x9c) [ 12.120491] [] (dump_stack) from [] (verify_new_ex+0xc4/0xdc) [ 12.128326] [] (verify_new_ex) from [] (devcgroup_access_write+0x374/0x658) [ 12.137426] [] (devcgroup_access_write) from [] (cgroup_file_write+0x28/0x1bc) [ 12.146796] [] (cgroup_file_write) from [] (kernfs_fop_write+0xc0/0x1b8) [ 12.155620] [] (kernfs_fop_write) from [] (__vfs_write+0x1c/0xd8) [ 12.163783] [] (__vfs_write) from [] (vfs_write+0x90/0x16c) [ 12.171426] [] (vfs_write) from [] (SyS_write+0x44/0x9c) [ 12.178806] [] (SyS_write) from [] (ret_fast_syscall+0x0/0x1c) Fix it by making sure rcu_read_lock() is held around devcgroup_update_access(). Signed-off-by: Felipe Balbi --- security/device_cgroup.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/security/device_cgroup.c b/security/device_cgroup.c index 73455089feef..0a6316b50357 100644 --- a/security/device_cgroup.c +++ b/security/device_cgroup.c @@ -766,8 +766,10 @@ static ssize_t devcgroup_access_write(struct kernfs_open_file *of, int retval; mutex_lock(&devcgroup_mutex); + rcu_read_lock(); retval = devcgroup_update_access(css_to_devcgroup(of_css(of)), of_cft(of)->private, strstrip(buf)); + rcu_read_unlock(); mutex_unlock(&devcgroup_mutex); return retval ?: nbytes; }