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: 08733a0cb7de ("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>

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index de4b8a75f30b03ee0a91f3980c975af8cf1ea78f..e9ffe33dc0cafa43c3a9759046b5df2da74e03d5 100644 (file)
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1337,6 +1337,12 @@ repeat:
                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 @@ repeat:
        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
-                       nf_ct_put(tmpl);
-       }
+       if (tmpl)
+               nf_ct_put(tmpl);
 
        return ret;
 }