Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756462Ab0KYBgI (ORCPT ); Wed, 24 Nov 2010 20:36:08 -0500 Received: from mx1.redhat.com ([209.132.183.28]:48779 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753348Ab0KYBgH (ORCPT ); Wed, 24 Nov 2010 20:36:07 -0500 Date: Wed, 24 Nov 2010 20:35:57 -0500 From: Dave Jones To: Linux Kernel , Andrew Morton Subject: rcu_read_lock/unlock protect find_task_by_vpid call in check_clock Message-ID: <20101125013557.GB2854@redhat.com> Mail-Followup-To: Dave Jones , Linux Kernel , Andrew Morton References: <20101125010948.GA1371@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20101125010948.GA1371@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1690 Lines: 49 =================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- kernel/pid.c:419 invoked rcu_dereference_check() without protection! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 1 1 lock held by scrashme/13382: #0: (tasklist_lock){.?.?..}, at: [] check_clock+0x46/0x9a stack backtrace: Pid: 13382, comm: scrashme Not tainted 2.6.37-rc3+ #8 Call Trace: [] lockdep_rcu_dereference+0x9d/0xa5 [] find_task_by_pid_ns+0x44/0x5d [] find_task_by_vpid+0x22/0x24 [] check_clock+0x4e/0x9a [] posix_cpu_clock_getres+0x16/0x41 [] sys_clock_getres+0x39/0xa0 [] system_call_fastpath+0x16/0x1b Signed-off-by: Dave Jones diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c index 6842eeb..4bef9aa 100644 --- a/kernel/posix-cpu-timers.c +++ b/kernel/posix-cpu-timers.c @@ -38,11 +38,13 @@ static int check_clock(const clockid_t which_clock) return 0; read_lock(&tasklist_lock); + rcu_read_lock(); p = find_task_by_vpid(pid); if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ? same_thread_group(p, current) : thread_group_leader(p))) { error = -EINVAL; } + rcu_read_unlock(); read_unlock(&tasklist_lock); return error; -- 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/