| Message ID | 1386792578-6968-1-git-send-email-kamal@canonical.com |
|---|---|
| State | New |
| Headers | show |
diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 0bf88e4..c219f8b 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -1724,8 +1724,12 @@ 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-3.8.y-queue branch of the 3.8.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-3.8.y-queue This patch is scheduled to be released in version 3.8.13.15. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.8.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From 1473b4958d4919e021159e2ca0a3a27e991f6f58 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() [ 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 <ast@plumgrid.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- net/ipv4/route.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) -- 1.8.3.2