Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760194AbaLLGR4 (ORCPT ); Fri, 12 Dec 2014 01:17:56 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:51890 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760041AbaLLGRT (ORCPT ); Fri, 12 Dec 2014 01:17:19 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Shivnandan Kumar" , "Stephen Smalley" , "Paul Moore" Date: Fri, 12 Dec 2014 06:14:25 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 062/164] selinux: fix inode security list corruption In-Reply-To: X-SA-Exim-Connect-IP: 2001:470:1f08:1539:c97:8151:cc89:c28d X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.65-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Stephen Smalley commit 923190d32de4428afbea5e5773be86bea60a9925 upstream. sb_finish_set_opts() can race with inode_free_security() when initializing inode security structures for inodes created prior to initial policy load or by the filesystem during ->mount(). This appears to have always been a possible race, but commit 3dc91d4 ("SELinux: Fix possible NULL pointer dereference in selinux_inode_permission()") made it more evident by immediately reusing the unioned list/rcu element of the inode security structure for call_rcu() upon an inode_free_security(). But the underlying issue was already present before that commit as a possible use-after-free of isec. Shivnandan Kumar reported the list corruption and proposed a patch to split the list and rcu elements out of the union as separate fields of the inode_security_struct so that setting the rcu element would not affect the list element. However, this would merely hide the issue and not truly fix the code. This patch instead moves up the deletion of the list entry prior to dropping the sbsec->isec_lock initially. Then, if the inode is dropped subsequently, there will be no further references to the isec. Reported-by: Shivnandan Kumar Signed-off-by: Stephen Smalley Signed-off-by: Paul Moore Signed-off-by: Ben Hutchings --- security/selinux/hooks.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -435,6 +435,7 @@ next_inode: list_entry(sbsec->isec_head.next, struct inode_security_struct, list); struct inode *inode = isec->inode; + list_del_init(&isec->list); spin_unlock(&sbsec->isec_lock); inode = igrab(inode); if (inode) { @@ -443,7 +444,6 @@ next_inode: iput(inode); } spin_lock(&sbsec->isec_lock); - list_del_init(&isec->list); goto next_inode; } spin_unlock(&sbsec->isec_lock); -- 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/