[PATCH net] netfilter: xt_TEE: fix NULL dereference

[PATCH net] netfilter: xt_TEE: fix NULL dereference

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

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>
---
 net/netfilter/xt_TEE.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/xt_TEE.c b/net/netfilter/xt_TEE.c
index fd980aa7715d..c5fdea18a9af 100644
--- 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;
 }

Re: [PATCH net] netfilter: xt_TEE: fix NULL dereference

[Pablo Neira Ayuso]

On Mon, Oct 19, 2015 at 06:02:01PM -0700, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> 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.

Applied here, will push it out after the pending pull request.

Thanks Eric.