netdev - [PATCH nf-next] netfilter: ctnetlink: must check mark attributes vs NULL

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Date:   Thu, 20 Sep 2018 23:53:06 +0200
From:   Florian Westphal <fw@...len.de>
To:     <netfilter-devel@...r.kernel.org>
Cc:     syzbot+e45eda8eda6e93a03959@...kaller.appspotmail.com,
        syzkaller-bugs@...glegroups.com, netdev@...r.kernel.org,
        kristian.evensen@...il.com, Florian Westphal <fw@...len.de>
Subject: [PATCH nf-next] netfilter: ctnetlink: must check mark attributes vs NULL

else we will oops (null deref) when the attributes aren't present.

Also add back the EOPNOTSUPP in case MARK filtering is requested but
kernel doesn't support it.

Fixes: 59c08c69c2788 ("netfilter: ctnetlink: Support L3 protocol-filter on flush")
Reported-by: syzbot+e45eda8eda6e93a03959@...kaller.appspotmail.com
Signed-off-by: Florian Westphal <fw@...len.de>
---
 only affects nf-next and linux-next.

 net/netfilter/nf_conntrack_netlink.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index f8c74f31aa36..b7a6984c74d0 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -833,6 +833,11 @@ ctnetlink_alloc_filter(const struct nlattr * const cda[], u8 family)
 {
 	struct ctnetlink_filter *filter;
 
+#ifndef CONFIG_NF_CONNTRACK_MARK
+	if (cda[CTA_MARK] && cda[CTA_MARK_MASK])
+		return ERR_PTR(-EOPNOTSUPP);
+#endif
+
 	filter = kzalloc(sizeof(*filter), GFP_KERNEL);
 	if (filter == NULL)
 		return ERR_PTR(-ENOMEM);
@@ -840,8 +845,10 @@ ctnetlink_alloc_filter(const struct nlattr * const cda[], u8 family)
 	filter->family = family;
 
 #ifdef CONFIG_NF_CONNTRACK_MARK
-	filter->mark.val = ntohl(nla_get_be32(cda[CTA_MARK]));
-	filter->mark.mask = ntohl(nla_get_be32(cda[CTA_MARK_MASK]));
+	if (cda[CTA_MARK] && cda[CTA_MARK_MASK]) {
+		filter->mark.val = ntohl(nla_get_be32(cda[CTA_MARK]));
+		filter->mark.mask = ntohl(nla_get_be32(cda[CTA_MARK_MASK]));
+	}
 #endif
 	return filter;
 }
-- 
2.16.4