Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752836AbbHaUkj (ORCPT ); Mon, 31 Aug 2015 16:40:39 -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 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 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2926 Lines: 61 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; } -- 2.5.0 -- 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/