From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161862Ab3LFWMM (ORCPT ); Fri, 6 Dec 2013 17:12:12 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:60923 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759373Ab3LFVxk (ORCPT ); Fri, 6 Dec 2013 16:53:40 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alexei Starovoitov , "David S. Miller" Subject: [PATCH 3.10 29/58] ipv4: fix race in concurrent ip_route_input_slow() Date: Fri, 6 Dec 2013 13:52:00 -0800 Message-Id: <20131206214847.599609797@linuxfoundation.org> X-Mailer: git-send-email 1.8.5.1.67.gb00d244 In-Reply-To: <20131206214844.906193530@linuxfoundation.org> References: <20131206214844.906193530@linuxfoundation.org> User-Agent: quilt/0.60-8.1.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Alexei Starovoitov [ Upstream commit dcdfdf56b4a6c9437fc37dbc9cee94a788f9b0c4 ] CPUs can ask for local route via ip_route_input_noref() concurrently. if nh_rth_input is not cached yet, CPUs will proceed to allocate equivalent DSTs on 'lo' and then will try to cache them in nh_rth_input via rt_cache_route() Most of the time they succeed, but on occasion the following two lines: orig = *p; prev = cmpxchg(p, orig, rt); in rt_cache_route() do race and one of the cpus fails to complete cmpxchg. But ip_route_input_slow() doesn't check the return code of rt_cache_route(), so dst is leaking. dst_destroy() is never called and 'lo' device refcnt doesn't go to zero, which can be seen in the logs as: unregister_netdevice: waiting for lo to become free. Usage count = 1 Adding mdelay() between above two lines makes it easily reproducible. Fix it similar to nh_pcpu_rth_output case. Fixes: d2d68ba9fe8b ("ipv4: Cache input routes in fib_info nexthops.") Signed-off-by: Alexei Starovoitov Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/route.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -1720,8 +1720,12 @@ local_input: rth->dst.error= -err; rth->rt_flags &= ~RTCF_LOCAL; } - if (do_cache) - rt_cache_route(&FIB_RES_NH(res), rth); + if (do_cache) { + if (unlikely(!rt_cache_route(&FIB_RES_NH(res), rth))) { + rth->dst.flags |= DST_NOCACHE; + rt_add_uncached_list(rth); + } + } skb_dst_set(skb, &rth->dst); err = 0; goto out;