[TIPC]: Enhance validation of format on incoming messages

This patch ensures that TIPC properly handles incoming messages
that have incorrect or unexpected formats.  Most significantly,
it now ensures that each sl_buff has at least as much data as
the message header indicates it should, and that the entire
message header is stored contiguously; this prevents TIPC from
accidentally accessing memory that is not part of the sk_buff.

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/tipc/link.c b/net/tipc/link.c
index 0873793..2a26a16 100644 (file)
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -1785,6 +1785,56 @@ static struct sk_buff *link_insert_deferred_queue(struct link *l_ptr,
        return buf;
 }
 
+/**
+ * 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, LONG_H_SIZE, DIR_MSG_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 (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);
+}
+
 void tipc_recv_msg(struct sk_buff *head, struct tipc_bearer *tb_ptr)
 {
        read_lock_bh(&tipc_net_lock);
@@ -1794,9 +1844,9 @@ void tipc_recv_msg(struct sk_buff *head, struct tipc_bearer *tb_ptr)
                struct link *l_ptr;
                struct sk_buff *crs;
                struct sk_buff *buf = head;
-               struct tipc_msg *msg = buf_msg(buf);
-               u32 seq_no = msg_seqno(msg);
-               u32 ackd = msg_ack(msg);
+               struct tipc_msg *msg;
+               u32 seq_no;
+               u32 ackd;
                u32 released = 0;
                int type;
 
@@ -1804,12 +1854,11 @@ void tipc_recv_msg(struct sk_buff *head, struct tipc_bearer *tb_ptr)
                TIPC_SKB_CB(buf)->handle = b_ptr;
 
                head = head->next;
-               if (unlikely(msg_version(msg) != TIPC_VERSION))
+
+               /* Ensure message is well-formed */
+
+               if (unlikely(!link_recv_buf_validate(buf)))
                        goto cont;
-#if 0
-               if (msg_user(msg) != LINK_PROTOCOL)
-#endif
-                       msg_dbg(msg,"<REC<");
 
                /* Ensure message data is a single contiguous unit */
 
@@ -1817,6 +1866,10 @@ void tipc_recv_msg(struct sk_buff *head, struct tipc_bearer *tb_ptr)
                        goto cont;
                }
 
+               /* Handle arrival of a non-unicast link message */
+
+               msg = buf_msg(buf);
+
                if (unlikely(msg_non_seq(msg))) {
                        link_recv_non_seq(buf);
                        continue;
@@ -1826,19 +1879,26 @@ void tipc_recv_msg(struct sk_buff *head, struct tipc_bearer *tb_ptr)
                             (msg_destnode(msg) != tipc_own_addr)))
                        goto cont;
 
+               /* Locate unicast link endpoint that should handle message */
+
                n_ptr = tipc_node_find(msg_prevnode(msg));
                if (unlikely(!n_ptr))
                        goto cont;
-
                tipc_node_lock(n_ptr);
+
                l_ptr = n_ptr->links[b_ptr->identity];
                if (unlikely(!l_ptr)) {
                        tipc_node_unlock(n_ptr);
                        goto cont;
                }
-               /*
-                * Release acked messages
-                */
+
+               /* Validate message sequence number info */
+
+               seq_no = msg_seqno(msg);
+               ackd = msg_ack(msg);
+
+               /* Release acked messages */
+
                if (less(n_ptr->bclink.acked, msg_bcast_ack(msg))) {
                        if (tipc_node_is_up(n_ptr) && n_ptr->bclink.supported)
                                tipc_bclink_acknowledge(n_ptr, msg_bcast_ack(msg));
@@ -1857,6 +1917,9 @@ void tipc_recv_msg(struct sk_buff *head, struct tipc_bearer *tb_ptr)
                        l_ptr->first_out = crs;
                        l_ptr->out_queue_size -= released;
                }
+
+               /* Try sending any messages link endpoint has pending */
+
                if (unlikely(l_ptr->next_out))
                        tipc_link_push_queue(l_ptr);
                if (unlikely(!list_empty(&l_ptr->waiting_ports)))
@@ -1866,6 +1929,8 @@ void tipc_recv_msg(struct sk_buff *head, struct tipc_bearer *tb_ptr)
                        tipc_link_send_proto_msg(l_ptr, STATE_MSG, 0, 0, 0, 0, 0);
                }
 
+               /* Now (finally!) process the incoming message */
+
 protocol_check:
                if (likely(link_working_working(l_ptr))) {
                        if (likely(seq_no == mod(l_ptr->next_in_no))) {