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dccp: limit sk_filter trim to payload

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Dccp verifies packet integrity, including length, at initial rcv in
dccp_invalid_packet, later pulls headers in dccp_enqueue_skb.

A call to sk_filter in-between can cause __skb_pull to wrap skb->len.
skb_copy_datagram_msg interprets this as a negative value, so
(correctly) fails with EFAULT. The negative length is reported in
ioctl SIOCINQ or possibly in a DCCP_WARN in dccp_close.

Introduce an sk_receive_skb variant that caps how small a filter
program can trim packets, and call this in dccp with the header
length. Excessively trimmed packets are now processed normally and
queued for reception as 0B payloads.

Fixes: 7c657876b6 ("[DCCP]: Initial implementation")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Willem de Bruijn
2016-07-12 18:18:57 -04:00
committed by David S. Miller
parent f4979fcea7
commit 4f0c40d944
4 changed files with 13 additions and 6 deletions
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8
include/net/sock.h
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@@ -1576,7 +1576,13 @@ static inline void sock_put(struct sock *sk)
*/
void sock_gen_put(struct sock *sk);
int sk_receive_skb(struct sock *sk, struct sk_buff *skb, const int nested);
int __sk_receive_skb(struct sock *sk, struct sk_buff *skb, const int nested,
unsigned int trim_cap);
static inline int sk_receive_skb(struct sock *sk, struct sk_buff *skb,
const int nested)
{
return __sk_receive_skb(sk, skb, nested, 1);
}
static inline void sk_tx_queue_set(struct sock *sk, int tx_queue)
{