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netfilter: conntrack: fix NF_REPEAT handling

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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: 08733a0cb7 ("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>
This commit is contained in:
Arnd Bergmann 2016-11-08 14:28:19 +01:00 committed by Pablo Neira Ayuso
parent 30f5815848
commit 56a62e2218
1 changed files with 8 additions and 10 deletions
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18
net/netfilter/nf_conntrack_core.c
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@ -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
nf_ct_put(tmpl);
}
if (tmpl)
nf_ct_put(tmpl);
return ret;
}