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[PATCH 3.2 3/4] dccp: fix freeing skb too early for IPV6_RECVPKTINFO

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3.2.86-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Andrey Konovalov <andreyknvl@google.com>

commit 5edabca9d4cff7f1f2b68f0bac55ef99d9798ba4 upstream.

In the current DCCP implementation an skb for a DCCP_PKT_REQUEST packet
is forcibly freed via __kfree_skb in dccp_rcv_state_process if
dccp_v6_conn_request successfully returns.

However, if IPV6_RECVPKTINFO is set on a socket, the address of the skb
is saved to ireq->pktopts and the ref count for skb is incremented in
dccp_v6_conn_request, so skb is still in use. Nevertheless, it gets freed
in dccp_rcv_state_process.

Fix by calling consume_skb instead of doing goto discard and therefore
calling __kfree_skb.

Similar fixes for TCP:

fb7e2399ec17f1004c0e0ccfd17439f8759ede01 [TCP]: skb is unexpectedly freed.
0aea76d35c9651d55bbaf746e7914e5f9ae5a25d tcp: SYN packets are now
simply consumed

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 net/dccp/input.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/dccp/input.c
+++ b/net/dccp/input.c
@@ -606,7 +606,8 @@ int dccp_rcv_state_process(struct sock *
 			if (inet_csk(sk)->icsk_af_ops->conn_request(sk,
 								    skb) < 0)
 				return 1;
-			goto discard;
+			consume_skb(skb);
+			return 0;
 		}
 		if (dh->dccph_type == DCCP_PKT_RESET)
 			goto discard;

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[PATCH 3.2 0/4] 3.2.86-rc1 review Ben Hutchings <ben@decadent.org.uk> - 2017-02-24 14:20 +0100
  [PATCH 3.2 2/4] USB: serial: kl5kusb105: fix line-state error  handling Ben Hutchings <ben@decadent.org.uk> - 2017-02-24 14:20 +0100
  [PATCH 3.2 1/4] kvm: nVMX: Allow L1 to intercept software  exceptions (#BP and #OF) Ben Hutchings <ben@decadent.org.uk> - 2017-02-24 14:20 +0100
  [PATCH 3.2 4/4] tcp: avoid infinite loop in tcp_splice_read() Ben Hutchings <ben@decadent.org.uk> - 2017-02-24 14:20 +0100
  [PATCH 3.2 3/4] dccp: fix freeing skb too early for IPV6_RECVPKTINFO Ben Hutchings <ben@decadent.org.uk> - 2017-02-24 14:20 +0100
  Re: [PATCH 3.2 0/4] 3.2.86-rc1 review Guenter Roeck <linux@roeck-us.net> - 2017-02-24 17:20 +0100
    Re: [PATCH 3.2 0/4] 3.2.86-rc1 review Ben Hutchings <ben@decadent.org.uk> - 2017-02-24 17:40 +0100

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