netfilter: xt_TEE: fix NULL dereference

iptables -I INPUT ... -j TEE --gateway 10.1.2.3

<crash> because --oif was not specified

tee_tg_check() sets ->priv pointer to NULL in this case.

Fixes: bbde9fc1824a ("netfilter: factor out packet duplication for IPv4/IPv6")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/xt_TEE.c b/net/netfilter/xt_TEE.c
index fd980aa7715dc76d66b75bf53b158c07b3a147ed..c5fdea18a9afbd8d98214c11e362875f0e9011ed 100644 (file)
--- a/net/netfilter/xt_TEE.c
+++ b/net/netfilter/xt_TEE.c
@@ -31,8 +31,9 @@ static unsigned int
 tee_tg4(struct sk_buff *skb, const struct xt_action_param *par)
 {
        const struct xt_tee_tginfo *info = par->targinfo;
+       int oif = info->priv ? info->priv->oif : 0;
 
-       nf_dup_ipv4(skb, par->hooknum, &info->gw.in, info->priv->oif);
+       nf_dup_ipv4(skb, par->hooknum, &info->gw.in, oif);
 
        return XT_CONTINUE;
 }
@@ -42,8 +43,9 @@ static unsigned int
 tee_tg6(struct sk_buff *skb, const struct xt_action_param *par)
 {
        const struct xt_tee_tginfo *info = par->targinfo;
+       int oif = info->priv ? info->priv->oif : 0;
 
-       nf_dup_ipv6(skb, par->hooknum, &info->gw.in6, info->priv->oif);
+       nf_dup_ipv6(skb, par->hooknum, &info->gw.in6, oif);
 
        return XT_CONTINUE;
 }