Commit 56a62e22 authored Nov 08, 2016 by Arnd Bergmann Committed by Pablo Neira Ayuso Nov 10, 2016

netfilter: conntrack: fix NF_REPEAT handling



gcc correctly identified a theoretical uninitialized variable use:

net/netfilter/nf_conntrack_core.c: In function 'nf_conntrack_in':
net/netfilter/nf_conntrack_core.c:1125:14: error: 'l4proto' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This could only happen when we 'goto out' before looking up l4proto,
and then enter the retry, implying that l3proto->get_l4proto()
returned NF_REPEAT. This does not currently get returned in any
code path and probably won't ever happen, but is not good to
rely on.

Moving the repeat handling up a little should have the same
behavior as today but avoids the warning by making that case
impossible to enter.

[ I have mangled this original patch to remove the check for tmpl, we
  should inconditionally jump back to the repeat label in case we hit
  NF_REPEAT instead. I have also moved the comment that explains this
  where it belongs. --pablo ]

Fixes: 08733a0c ("netfilter: handle NF_REPEAT from nf_conntrack_in()")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

parent 30f58158

net/netfilter/nf_conntrack_core.c

+8 −10

Original line number	Diff line number	Diff line
		@@ -1337,6 +1337,12 @@ nf_conntrack_in(struct net *net, u_int8_t pf, unsigned int hooknum,
		NF_CT_STAT_INC_ATOMIC(net, invalid);
		if (ret == -NF_DROP)
		NF_CT_STAT_INC_ATOMIC(net, drop);
		/* Special case: TCP tracker reports an attempt to reopen a
		* closed/aborted connection. We have to go back and create a
		* fresh conntrack.
		*/
		if (ret == -NF_REPEAT)
		goto repeat;
		ret = -ret;
		goto out;
		}
		@@ -1344,16 +1350,8 @@ nf_conntrack_in(struct net *net, u_int8_t pf, unsigned int hooknum,
		if (set_reply && !test_and_set_bit(IPS_SEEN_REPLY_BIT, &ct->status))
		nf_conntrack_event_cache(IPCT_REPLY, ct);
		out:
		if (tmpl) {
		/* Special case: TCP tracker reports an attempt to reopen a
		* closed/aborted connection. We have to go back and create a
		* fresh conntrack.
		*/
		if (ret == NF_REPEAT)
		goto repeat;
		else
		if (tmpl)
		nf_ct_put(tmpl);
		}

		return ret;
		}