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bridge: ebtables: don't crash when using dnat target in output chains

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xt_in() returns NULL in the output hook, skip the pkt_type change for
that case, redirection only makes sense in broute/prerouting hooks.

Reported-by: Tom Yan <tom.ty89@gmail.com>
Cc: Linus Lüssing <linus.luessing@c0d3.blue>
Fixes: cf3cb246e2 ("bridge: ebtables: fix reception of frames DNAT-ed to bridge device/port")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2019-11-03 20:54:28 +01:00 committed by Pablo Neira Ayuso
parent 9fedd894b4
commit b23c0742c2
1 changed files with 15 additions and 4 deletions
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19
net/bridge/netfilter/ebt_dnat.c
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@ -20,7 +20,6 @@ static unsigned int
ebt_dnat_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
const struct ebt_nat_info *info = par->targinfo;
struct net_device *dev;
if (skb_ensure_writable(skb, ETH_ALEN))
return EBT_DROP;
@ -33,10 +32,22 @@ ebt_dnat_tg(struct sk_buff *skb, const struct xt_action_param *par)
else
skb->pkt_type = PACKET_MULTICAST;
} else {
if (xt_hooknum(par) != NF_BR_BROUTING)
dev = br_port_get_rcu(xt_in(par))->br->dev;
else
const struct net_device *dev;
switch (xt_hooknum(par)) {
case NF_BR_BROUTING:
dev = xt_in(par);
break;
case NF_BR_PRE_ROUTING:
dev = br_port_get_rcu(xt_in(par))->br->dev;
break;
default:
dev = NULL;
break;
}
if (!dev) /* NF_BR_LOCAL_OUT */
return info->target;
if (ether_addr_equal(info->mac, dev->dev_addr))
skb->pkt_type = PACKET_HOST;