x25: Patch to fix bug 15678 - x25 accesses fields beyond end of packet.

Here is a patch to stop X.25 examining fields beyond the end of the packet.

For example, when a simple CALL ACCEPTED was received:

	10 10 0f

x25_parse_facilities was attempting to decode the FACILITIES field, but this
packet contains no facilities field.

Signed-off-by: John Hughes <john@calva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 4 deletions

diff --git a/net/x25/x25_in.c b/net/x25/x25_in.c
index 96d922783547..b39072f3a297 100644
--- a/net/x25/x25_in.c
+++ b/net/x25/x25_in.c
@@ -89,6 +89,7 @@ static int x25_queue_rx_frame(struct sock *sk, struct sk_buff *skb, int more)
 static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametype)
 {
         struct x25_address source_addr, dest_addr;
+        int len;
 
         switch (frametype) {
                 case X25_CALL_ACCEPTED: {
@@ -106,11 +107,17 @@ static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametyp
                          *      Parse the data in the frame.
                          */
                         skb_pull(skb, X25_STD_MIN_LEN);
-                        skb_pull(skb, x25_addr_ntoa(skb->data, &source_addr, &dest_addr));
-                        skb_pull(skb,
-                                 x25_parse_facilities(skb, &x25->facilities,
+
+                        len = x25_parse_address_block(skb, &source_addr,
+                                                &dest_addr);
+                        if (len > 0)
+                                skb_pull(skb, len);
+
+                        len = x25_parse_facilities(skb, &x25->facilities,
                                                 &x25->dte_facilities,
-                                                &x25->vc_facil_mask));
+                                                &x25->vc_facil_mask);
+                        if (len > 0)
+                                skb_pull(skb, len);
                         /*
                          *      Copy any Call User Data.
                          */