llc: llc_cmsg_rcv was getting called after sk_eat_skb.

Received non stream protocol packets were calling llc_cmsg_rcv that used a
skb after that skb was released by sk_eat_skb. This caused received STP
packets to generate kernel panics.
Signed-off-by: NAlexandru Juncu <ajuncu@ixiacom.com>
Signed-off-by: NKunjan Naik <knaik@ixiacom.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/llc/af_llc.c

@@ -833,15 +833,15 @@ static int llc_ui_recvmsg(struct kiocb *iocb, struct socket *sock,
 		copied += used;
 		len -= used;
 
+		/* For non stream protcols we get one packet per recvmsg call */
+		if (sk->sk_type != SOCK_STREAM)
+			goto copy_uaddr;
+
 		if (!(flags & MSG_PEEK)) {
 			sk_eat_skb(sk, skb, 0);
 			*seq = 0;
 		}
 
-		/* For non stream protcols we get one packet per recvmsg call */
-		if (sk->sk_type != SOCK_STREAM)
-			goto copy_uaddr;
-
 		/* Partial read */
 		if (used + offset < skb->len)
 			continue;
@@ -857,6 +857,12 @@ static int llc_ui_recvmsg(struct kiocb *iocb, struct socket *sock,
 	}
 	if (llc_sk(sk)->cmsg_flags)
 		llc_cmsg_rcv(msg, skb);
+
+	if (!(flags & MSG_PEEK)) {
+			sk_eat_skb(sk, skb, 0);
+			*seq = 0;
+	}
+
 	goto out;
 }