From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753937Ab3LNQcZ (ORCPT ); Sat, 14 Dec 2013 11:32:25 -0500 Received: from mx1.redhat.com ([209.132.183.28]:22775 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753729Ab3LNQcY (ORCPT ); Sat, 14 Dec 2013 11:32:24 -0500 Date: Sat, 14 Dec 2013 17:33:17 +0100 From: Oleg Nesterov To: Paul Moore Cc: Stephen Smalley , James Morris , Eric Paris , Evan McNabb , Jan Stancek , linux-kernel@vger.kernel.org Subject: [PATCH v2] selinux: selinux_setprocattr()->ptrace_parent() needs rcu_read_lock() Message-ID: <20131214163317.GB21675@redhat.com> References: <20131205165953.GA24844@redhat.com> <2222358.CI2sulrSvj@sifl> <20131206144735.GA2674@redhat.com> <20131214163256.GA21675@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131214163256.GA21675@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org selinux_setprocattr() does ptrace_parent(p) under task_lock(p), but task_struct->alloc_lock doesn't pin ->parent or ->ptrace, this looks confusing and triggers the "suspicious RCU usage" warning because ptrace_parent() does rcu_dereference_check(). And in theory this is wrong, spin_lock()->preempt_disable() doesn't necessarily imply rcu_read_lock() we need to access the ->parent. Reported-by: Evan McNabb Signed-off-by: Oleg Nesterov --- security/selinux/hooks.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -5503,11 +5503,11 @@ static int selinux_setprocattr(struct ta /* Check for ptracing, and update the task SID if ok. Otherwise, leave SID unchanged and fail. */ ptsid = 0; - task_lock(p); + rcu_read_lock(); tracer = ptrace_parent(p); if (tracer) ptsid = task_sid(tracer); - task_unlock(p); + rcu_read_unlock(); if (tracer) { error = avc_has_perm(ptsid, sid, SECCLASS_PROCESS,