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netfilter: ebtables: Fix extension lookup with identical name

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If a requested extension exists as module and is not loaded,
ebt_check_match() might accidentally use an NFPROTO_UNSPEC one with same
name and fail.

Reproduced with limit match: Given xt_limit and ebt_limit both built as
module, the following would fail:

  modprobe xt_limit
  ebtables -I INPUT --limit 1/s -j ACCEPT

The fix is to make ebt_check_match() distrust a found NFPROTO_UNSPEC
extension and retry after requesting an appropriate module.

Cc: Florian Westphal <fw@strlen.de>
Signed-off-by: Phil Sutter <phil@nwl.cc>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Phil Sutter 2016-04-12 01:31:14 +02:00 committed by Pablo Neira Ayuso
parent 644c7e48cb
commit bcf4934288
1 changed files with 5 additions and 1 deletions
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6
net/bridge/netfilter/ebtables.c
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@ -370,7 +370,11 @@ ebt_check_match(struct ebt_entry_match *m, struct xt_mtchk_param *par,
left - sizeof(struct ebt_entry_match) < m->match_size)
return -EINVAL;
match = xt_request_find_match(NFPROTO_BRIDGE, m->u.name, 0);
match = xt_find_match(NFPROTO_BRIDGE, m->u.name, 0);
if (IS_ERR(match) || match->family != NFPROTO_BRIDGE) {
request_module("ebt_%s", m->u.name);
match = xt_find_match(NFPROTO_BRIDGE, m->u.name, 0);
}
if (IS_ERR(match))
return PTR_ERR(match);
m->u.match = match;