[FIX 1/1] sip: add missing RCU reader lock

[Holger Eitzenberger <holger@eitzenberger.org>]

[-- Attachment #1: sip-add-missing-RCU-reader-lock.diff --]
[-- Type: text/plain, Size: 984 bytes --]

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 properly by
the RCU reader lock, but the 2nd isn't.

I chose to not just extend the first RCU protected area but putting
the rcu_read_unlock() down, because there is a 'return' in between.

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
@@ -983,6 +983,7 @@ static int set_expected_rtp_rtcp(struct
 	if (skip_expect)
 		return NF_ACCEPT;
 
+	rcu_read_lock();
 	rtp_exp = nf_ct_expect_alloc(ct);
 	if (rtp_exp == NULL)
 		goto err1;
@@ -1012,6 +1013,7 @@ static int set_expected_rtp_rtcp(struct
 err2:
 	nf_ct_expect_put(rtp_exp);
 err1:
+	rcu_read_unlock();
 	return ret;
 }