dccp: limit sk_filter trim to payload
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: 7c657876b63c ("[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>
diff --git a/net/core/sock.c b/net/core/sock.c
index b7f1263..25dab8b 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -452,11 +452,12 @@
}
EXPORT_SYMBOL(sock_queue_rcv_skb);
-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)
{
int rc = NET_RX_SUCCESS;
- if (sk_filter(sk, skb))
+ if (sk_filter_trim_cap(sk, skb, trim_cap))
goto discard_and_relse;
skb->dev = NULL;
@@ -492,7 +493,7 @@
kfree_skb(skb);
goto out;
}
-EXPORT_SYMBOL(sk_receive_skb);
+EXPORT_SYMBOL(__sk_receive_skb);
struct dst_entry *__sk_dst_check(struct sock *sk, u32 cookie)
{