| Message ID | 1386772814-8584-1-git-send-email-luis.henriques@canonical.com |
|---|---|
| State | New |
| Headers | show |
diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 2de16d9..52e15e8 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -1774,8 +1774,12 @@ 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;
This is a note to let you know that I have just added a patch titled ipv4: fix race in concurrent ip_route_input_slow() to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.11.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From 5503a70e444f803335e09658718dc387075e7fe8 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov <ast@plumgrid.com> Date: Tue, 19 Nov 2013 19:12:34 -0800 Subject: ipv4: fix race in concurrent ip_route_input_slow() commit dcdfdf56b4a6c9437fc37dbc9cee94a788f9b0c4 upstream. 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 <ast@plumgrid.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- net/ipv4/route.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) -- 1.8.3.2