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>
struct sk_buff *build_skb(void *data, unsigned int frag_size)
{
	struct sk_buff *skb = __build_skb(data, frag_size);

	if (skb && frag_size) {
		skb->head_frag = 1;
		if (page_is_pfmemalloc(virt_to_head_page(data)))
			skb->pfmemalloc = 1;
	}
	return skb;
}

struct sk_buff *build_skb(void *data, unsigned int frag_size)
{
	struct sk_buff *skb = __build_skb(data, frag_size);

	if (skb && frag_size) {
		skb->head_frag = 1;
		if (page_is_pfmemalloc(virt_to_head_page(data)))
			skb->pfmemalloc = 1;
	}
	return skb;
}
