Phonet: fix aligned-mode pipe socket buffer header reserve

When the pipe uses aligned-mode data packets, we must reserve 4 bytes
instead of 3 for the pipe protocol header. Otherwise the Phonet header
would not be aligned, resulting in potentially corrupted headers with
later unaligned memory writes.

Signed-off-by: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/phonet/pep.c

@@ -1055,7 +1055,7 @@ static int pep_sendmsg(struct kiocb *iocb, struct sock *sk,
 	if (!skb)
 		return err;
 
-	skb_reserve(skb, MAX_PHONET_HEADER + 3);
+	skb_reserve(skb, MAX_PHONET_HEADER + 3 + pn->aligned);
 	err = memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len);
 	if (err < 0)
 		goto outfree;