| From | Greg Kroah-Hartman <> | Subject | [ 025/187] l2tp: fix a race in l2tp_ip_sendmsg() | Date | Thu, 12 Jul 2012 15:33:01 -0700 |
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From: Greg KH <gregkh@linuxfoundation.org>
3.4-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet <edumazet@google.com>
[ Upstream commit 4399a4df98a63e30fd16e9d0cecc46ea92269e8f ]
Commit 081b1b1bb27f (l2tp: fix l2tp_ip_sendmsg() route handling) added a race, in case IP route cache is disabled.
In this case, we should not do the dst_release(&rt->dst), since it'll free the dst immediately, instead of waiting a RCU grace period.
Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: James Chapman <jchapman@katalix.com> Cc: Denys Fedoryshchenko <denys@visp.net.lb> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- net/l2tp/l2tp_ip.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
--- a/net/l2tp/l2tp_ip.c +++ b/net/l2tp/l2tp_ip.c @@ -516,10 +516,12 @@ static int l2tp_ip_sendmsg(struct kiocb sk->sk_bound_dev_if); if (IS_ERR(rt)) goto no_route; - if (connected) + if (connected) { sk_setup_caps(sk, &rt->dst); - else - dst_release(&rt->dst); /* safe since we hold rcu_read_lock */ + } else { + skb_dst_set(skb, &rt->dst); + goto xmit; + } } /* We dont need to clone dst here, it is guaranteed to not disappear. @@ -527,6 +529,7 @@ static int l2tp_ip_sendmsg(struct kiocb */ skb_dst_set_noref(skb, &rt->dst); +xmit: /* Queue the packet to IP for output */ rc = ip_queue_xmit(skb, &inet->cork.fl); rcu_read_unlock();
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