From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965352AbcHNLz1 (ORCPT ); Sun, 14 Aug 2016 07:55:27 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:52345 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933276AbcHNLaY (ORCPT ); Sun, 14 Aug 2016 07:30:24 -0400 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, "Herbert Xu" , "David S. Miller" , "Baozeng Ding" , "Cong Wang" Date: Sat, 13 Aug 2016 18:42:51 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 088/305] netlink: Fix dump skb leak/double free In-Reply-To: X-SA-Exim-Connect-IP: 92.40.249.202 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 3.16.37-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Herbert Xu commit 92964c79b357efd980812c4de5c1fd2ec8bb5520 upstream. When we free cb->skb after a dump, we do it after releasing the lock. This means that a new dump could have started in the time being and we'll end up freeing their skb instead of ours. This patch saves the skb and module before we unlock so we free the right memory. Fixes: 16b304f3404f ("netlink: Eliminate kmalloc in netlink dump operation.") Reported-by: Baozeng Ding Signed-off-by: Herbert Xu Acked-by: Cong Wang Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- net/netlink/af_netlink.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -2693,6 +2693,7 @@ static int netlink_dump(struct sock *sk) struct netlink_callback *cb; struct sk_buff *skb = NULL; struct nlmsghdr *nlh; + struct module *module; int len, err = -ENOBUFS; int alloc_min_size; int alloc_size; @@ -2773,9 +2774,11 @@ static int netlink_dump(struct sock *sk) cb->done(cb); nlk->cb_running = false; + module = cb->module; + skb = cb->skb; mutex_unlock(nlk->cb_mutex); - module_put(cb->module); - consume_skb(cb->skb); + module_put(module); + consume_skb(skb); return 0; errout_skb: