[FIX V2] sip: add missing RCU reader lock

[Holger Eitzenberger <holger@eitzenberger.org>]

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Hi,

I noticed that set_expected_rtp_rtcp() in net-next misses a 2nd
RCU reader lock when dereferencing the 2nd hook function.  Same
bug is present in kernel v3.8 at least.

This is a resend, which extend the RCU protected area as needed.

Please check.

 /Holger


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sip: add missing RCU reader lock in set_expected_rtp_rtcp()

Currently set_expected_rtp_rtcp() in the SIP helper uses
rcu_dereference() two times to access two different NAT hook
functions.  However, only the first one is protected by the RCU
reader lock, but the 2nd isn't.

Fix it by extending the RCU protected area.

Signed-off-by: Holger Eitzenberger <holger.eitzenberger@sophos.com>

Index: net-next/net/netfilter/nf_conntrack_sip.c
===================================================================
--- net-next.orig/net/netfilter/nf_conntrack_sip.c
+++ net-next/net/netfilter/nf_conntrack_sip.c
@@ -966,7 +966,6 @@ static int set_expected_rtp_rtcp(struct
 #endif
 			skip_expect = 1;
 	} while (!skip_expect);
-	rcu_read_unlock();
 
 	base_port = ntohs(tuple.dst.u.udp.port) & ~1;
 	rtp_port = htons(base_port);
@@ -980,8 +979,10 @@ static int set_expected_rtp_rtcp(struct
 			goto err1;
 	}
 
-	if (skip_expect)
+	if (skip_expect) {
+		rcu_read_unlock();
 		return NF_ACCEPT;
+	}
 
 	rtp_exp = nf_ct_expect_alloc(ct);
 	if (rtp_exp == NULL)
@@ -1012,6 +1013,7 @@ static int set_expected_rtp_rtcp(struct
 err2:
 	nf_ct_expect_put(rtp_exp);
 err1:
+	rcu_read_unlock();
 	return ret;
 }