tipc: move message validation function to msg.c

The function link_buf_validate() is in reality re-entrant and context
independent, and will in later commits be called from several locations.
Therefore, we move it to msg.c, make it outline and rename the it to
tipc_msg_validate().

We also redesign the function to make proper use of pskb_may_pull()
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/link.c

@@ -1047,61 +1047,6 @@ static void link_retrieve_defq(struct tipc_link *link,
 		skb_queue_splice_tail_init(&link->deferred_queue, list);
 }
 
-/**
- * link_recv_buf_validate - validate basic format of received message
- *
- * This routine ensures a TIPC message has an acceptable header, and at least
- * as much data as the header indicates it should.  The routine also ensures
- * that the entire message header is stored in the main fragment of the message
- * buffer, to simplify future access to message header fields.
- *
- * Note: Having extra info present in the message header or data areas is OK.
- * TIPC will ignore the excess, under the assumption that it is optional info
- * introduced by a later release of the protocol.
- */
-static int link_recv_buf_validate(struct sk_buff *buf)
-{
-	static u32 min_data_hdr_size[8] = {
-		SHORT_H_SIZE, MCAST_H_SIZE, NAMED_H_SIZE, BASIC_H_SIZE,
-		MAX_H_SIZE, MAX_H_SIZE, MAX_H_SIZE, MAX_H_SIZE
-		};
-
-	struct tipc_msg *msg;
-	u32 tipc_hdr[2];
-	u32 size;
-	u32 hdr_size;
-	u32 min_hdr_size;
-
-	/* If this packet comes from the defer queue, the skb has already
-	 * been validated
-	 */
-	if (unlikely(TIPC_SKB_CB(buf)->deferred))
-		return 1;
-
-	if (unlikely(buf->len < MIN_H_SIZE))
-		return 0;
-
-	msg = skb_header_pointer(buf, 0, sizeof(tipc_hdr), tipc_hdr);
-	if (msg == NULL)
-		return 0;
-
-	if (unlikely(msg_version(msg) != TIPC_VERSION))
-		return 0;
-
-	size = msg_size(msg);
-	hdr_size = msg_hdr_sz(msg);
-	min_hdr_size = msg_isdata(msg) ?
-		min_data_hdr_size[msg_type(msg)] : INT_H_SIZE;
-
-	if (unlikely((hdr_size < min_hdr_size) ||
-		     (size < hdr_size) ||
-		     (buf->len < size) ||
-		     (size - hdr_size > TIPC_MAX_USER_MSG_SIZE)))
-		return 0;
-
-	return pskb_may_pull(buf, hdr_size);
-}
-
 /**
  * tipc_rcv - process TIPC packets/messages arriving from off-node
  * @net: the applicable net namespace
@@ -1127,7 +1072,7 @@ void tipc_rcv(struct net *net, struct sk_buff *skb, struct tipc_bearer *b_ptr)
 
 	while ((skb = __skb_dequeue(&head))) {
 		/* Ensure message is well-formed */
-		if (unlikely(!link_recv_buf_validate(skb)))
+		if (unlikely(!tipc_msg_validate(skb)))
 			goto discard;
 
 		/* Ensure message data is a single contiguous unit */
@@ -1398,7 +1343,6 @@ static void link_handle_out_of_seq_msg(struct tipc_link *l_ptr,
 
 	if (tipc_link_defer_pkt(&l_ptr->deferred_queue, buf)) {
 		l_ptr->stats.deferred_recv++;
-		TIPC_SKB_CB(buf)->deferred = true;
 		if ((skb_queue_len(&l_ptr->deferred_queue) % 16) == 1)
 			tipc_link_proto_xmit(l_ptr, STATE_MSG, 0, 0, 0, 0, 0);
 	} else {

net/tipc/msg.c

 /*
  * net/tipc/msg.c: TIPC message header routines
  *
- * Copyright (c) 2000-2006, 2014, Ericsson AB
+ * Copyright (c) 2000-2006, 2014-2015, Ericsson AB
  * Copyright (c) 2005, 2010-2011, Wind River Systems
  * All rights reserved.
  *
@@ -181,6 +181,48 @@ int tipc_buf_append(struct sk_buff **headbuf, struct sk_buff **buf)
 	return 0;
 }
 
+/* tipc_msg_validate - validate basic format of received message
+ *
+ * This routine ensures a TIPC message has an acceptable header, and at least
+ * as much data as the header indicates it should.  The routine also ensures
+ * that the entire message header is stored in the main fragment of the message
+ * buffer, to simplify future access to message header fields.
+ *
+ * Note: Having extra info present in the message header or data areas is OK.
+ * TIPC will ignore the excess, under the assumption that it is optional info
+ * introduced by a later release of the protocol.
+ */
+bool tipc_msg_validate(struct sk_buff *skb)
+{
+	struct tipc_msg *msg;
+	int msz, hsz;
+
+	if (unlikely(TIPC_SKB_CB(skb)->validated))
+		return true;
+	if (unlikely(!pskb_may_pull(skb, MIN_H_SIZE)))
+		return false;
+
+	hsz = msg_hdr_sz(buf_msg(skb));
+	if (unlikely(hsz < MIN_H_SIZE) || (hsz > MAX_H_SIZE))
+		return false;
+	if (unlikely(!pskb_may_pull(skb, hsz)))
+		return false;
+
+	msg = buf_msg(skb);
+	if (unlikely(msg_version(msg) != TIPC_VERSION))
+		return false;
+
+	msz = msg_size(msg);
+	if (unlikely(msz < hsz))
+		return false;
+	if (unlikely((msz - hsz) > TIPC_MAX_USER_MSG_SIZE))
+		return false;
+	if (unlikely(skb->len < msz))
+		return false;
+
+	TIPC_SKB_CB(skb)->validated = true;
+	return true;
+}
 
 /**
  * tipc_msg_build - create buffer chain containing specified header and data

net/tipc/msg.h

 /*
  * net/tipc/msg.h: Include file for TIPC message header routines
  *
- * Copyright (c) 2000-2007, 2014, Ericsson AB
+ * Copyright (c) 2000-2007, 2014-2015 Ericsson AB
  * Copyright (c) 2005-2008, 2010-2011, Wind River Systems
  * All rights reserved.
  *
@@ -92,7 +92,7 @@ struct plist;
 struct tipc_skb_cb {
 	void *handle;
 	struct sk_buff *tail;
-	bool deferred;
+	bool validated;
 	bool wakeup_pending;
 	bool bundling;
 	u16 chain_sz;
@@ -758,6 +758,7 @@ static inline u32 msg_tot_origport(struct tipc_msg *m)
 }
 
 struct sk_buff *tipc_buf_acquire(u32 size);
+bool tipc_msg_validate(struct sk_buff *skb);
 bool tipc_msg_reverse(u32 own_addr, struct sk_buff *buf, u32 *dnode,
 		      int err);
 void tipc_msg_init(u32 own_addr, struct tipc_msg *m, u32 user, u32 type,