When the cgroup matching code in nft_meta is called without a socket to
look at, it currently bails out and lets the packet pass. This is bad,
because the reason for skb->sk being NULL is simply that the packet was
directed to a socket that hasn't been looked up yet by early demux.
This patch does two things:
a) it uses the newly introduced pkt->sk pointer rather than skb->sk
to check for the net class ID. This allows us to look at the socket
the user passed into nf_hook().
b) in case the socket can't be accessed, it marks the skb as
'nf_postponed', so that later dispatchers have a chance to
re-iterate the chain for such packets, after a full demux was
conducted.
Note that the added flag in 'struct skb' does not increase the size
of the struct, as it fits in the 'flags1' bitfield.
Signed-off-by: Daniel Mack <dan...@zonque.org>
---
include/linux/skbuff.h | 3 ++-
net/netfilter/nft_meta.c | 9 ++++++---
2 files changed, 8 insertions(+), 4 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2738d35..3590101 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -584,7 +584,8 @@ struct sk_buff {
fclone:2,
peeked:1,
head_frag:1,
- xmit_more:1;
+ xmit_more:1,
+ nf_postponed:1;
/* one bit hole */
kmemcheck_bitfield_end(flags1);
diff --git a/net/netfilter/nft_meta.c b/net/netfilter/nft_meta.c
index cb2f13e..33b8d23 100644
--- a/net/netfilter/nft_meta.c
+++ b/net/netfilter/nft_meta.c
@@ -29,8 +29,9 @@ void nft_meta_get_eval(const struct nft_expr *expr,
const struct nft_pktinfo *pkt)
{
const struct nft_meta *priv = nft_expr_priv(expr);
- const struct sk_buff *skb = pkt->skb;
const struct net_device *in = pkt->in, *out = pkt->out;
+ struct sk_buff *skb = pkt->skb;
+ struct sock *sk = pkt->sk;
u32 *dest = ®s->data[priv->dreg];
switch (priv->key) {
@@ -168,9 +169,11 @@ void nft_meta_get_eval(const struct nft_expr *expr,
break;
#ifdef CONFIG_CGROUP_NET_CLASSID
case NFT_META_CGROUP:
- if (skb->sk == NULL || !sk_fullsock(skb->sk))
+ if (sk == NULL || !sk_fullsock(sk)) {
+ skb->nf_postponed = 1;
goto err;
- *dest = skb->sk->sk_classid;
+ }
+ *dest = sk->sk_classid;
break;
#endif
default:
--
2.5.0
--
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