Code: void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
	struct sk_buff *skb)
{
	int need_software_tstamp = sock_flag(sk, SOCK_RCVTSTAMP);
	struct scm_timestamping tss;
	int empty = 1;
	struct skb_shared_hwtstamps *shhwtstamps =
		skb_hwtstamps(skb);

	/* Race occurred between timestamp enabling and packet
	   receiving.  Fill in the current time for now. */
	if (need_software_tstamp && skb->tstamp == 0)
		__net_timestamp(skb);

	if (need_software_tstamp) {
		if (!sock_flag(sk, SOCK_RCVTSTAMPNS)) {
			struct timeval tv;
			skb_get_timestamp(skb, &tv);
			put_cmsg(msg, SOL_SOCKET, SCM_TIMESTAMP,
				 sizeof(tv), &tv);
		} else {
			struct timespec ts;
			skb_get_timestampns(skb, &ts);
			put_cmsg(msg, SOL_SOCKET, SCM_TIMESTAMPNS,
				 sizeof(ts), &ts);
		}
	}

	memset(&tss, 0, sizeof(tss));
	if ((sk->sk_tsflags & SOF_TIMESTAMPING_SOFTWARE) &&
	    ktime_to_timespec_cond(skb->tstamp, tss.ts + 0))
		empty = 0;
	if (shhwtstamps &&
	    (sk->sk_tsflags & SOF_TIMESTAMPING_RAW_HARDWARE) &&
	    ktime_to_timespec_cond(shhwtstamps->hwtstamp, tss.ts + 2))
		empty = 0;
	if (!empty) {
 		put_cmsg(msg, SOL_SOCKET,
 			 SCM_TIMESTAMPING, sizeof(tss), &tss);
 
		if (skb->len && (sk->sk_tsflags & SOF_TIMESTAMPING_OPT_STATS))
 			put_cmsg(msg, SOL_SOCKET, SCM_TIMESTAMPING_OPT_STATS,
 				 skb->len, skb->data);
 	}
}

Vulnerability Type: DoS +Info 
CWE ID: CWE-125
Summary: The TCP stack in the Linux kernel through 4.10.6 mishandles the SCM_TIMESTAMPING_OPT_STATS feature, which allows local users to obtain sensitive information from the kernel's internal socket data structures or cause a denial of service (out-of-bounds read) via crafted system calls, related to net/core/skbuff.c and net/socket.c.
Commit Message: tcp: fix SCM_TIMESTAMPING_OPT_STATS for normal skbs

__sock_recv_timestamp can be called for both normal skbs (for
receive timestamps) and for skbs on the error queue (for transmit
timestamps).

Commit 1c885808e456
(tcp: SOF_TIMESTAMPING_OPT_STATS option for SO_TIMESTAMPING)
assumes any skb passed to __sock_recv_timestamp are from
the error queue, containing OPT_STATS in the content of the skb.
This results in accessing invalid memory or generating junk
data.

To fix this, set skb->pkt_type to PACKET_OUTGOING for packets
on the error queue. This is safe because on the receive path
on local sockets skb->pkt_type is never set to PACKET_OUTGOING.
With that, copy OPT_STATS from a packet, only if its pkt_type
is PACKET_OUTGOING.

Fixes: 1c885808e456 ("tcp: SOF_TIMESTAMPING_OPT_STATS option for SO_TIMESTAMPING")
Reported-by: JongHwan Kim <zzoru007@gmail.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>