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@syzkaller.appspotmail.com
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 099a450e26be8fd149d223c099617faa9c2cadfd..4ae8e528943aca9f1881c3b4f77e5ebc231ebe14 100644 (file)
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -832,6 +832,11 @@ 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);
@@ -839,8 +844,10 @@ 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;
 }