tipc: Prevent access of non-existent field in short message header

This patch eliminates a case where TIPC's link code could try reading
a field that is not present in a short message header.  (The random
value obtained was not being used, but the read operation could result
in an invalid memory access exception in extremely rare circumstances.)

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

1 files changed, 3 insertions, 1 deletions

diff --git a/net/tipc/link.c b/net/tipc/link.c
index c62ebfea9304..022cb2f107ac 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -2674,10 +2674,12 @@ int tipc_link_send_long_buf(struct link *l_ptr, struct sk_buff *buf)
         u32 pack_sz = link_max_pkt(l_ptr);
         u32 fragm_sz = pack_sz - INT_H_SIZE;
         u32 fragm_no = 1;
-        u32 destaddr = msg_destnode(inmsg);
+        u32 destaddr;
 
         if (msg_short(inmsg))
                 destaddr = l_ptr->addr;
+        else
+                destaddr = msg_destnode(inmsg);
 
         if (msg_routed(inmsg))
                 msg_set_prevnode(inmsg, tipc_own_addr);