tipc: add NULL pointer check to prevent kernel oops

Calling:
tipc_node_link_down()->
   - tipc_node_write_unlock()->tipc_mon_peer_down()
   - tipc_mon_peer_down()
  just after disabling bearer could be caused kernel oops.

Fix this by adding a sanity check to make sure valid memory
access.

Acked-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: Hoang Le <hoang.h.le@dektech.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/tipc/monitor.c b/net/tipc/monitor.c
index 58708b4..6dce2ab 100644 (file)
--- a/net/tipc/monitor.c
+++ b/net/tipc/monitor.c
@@ -322,9 +322,13 @@ static void mon_assign_roles(struct tipc_monitor *mon, struct tipc_peer *head)
 void tipc_mon_remove_peer(struct net *net, u32 addr, int bearer_id)
 {
        struct tipc_monitor *mon = tipc_monitor(net, bearer_id);
-       struct tipc_peer *self = get_self(net, bearer_id);
+       struct tipc_peer *self;
        struct tipc_peer *peer, *prev, *head;
 
+       if (!mon)
+               return;
+
+       self = get_self(net, bearer_id);
        write_lock_bh(&mon->lock);
        peer = get_peer(mon, addr);
        if (!peer)
@@ -407,11 +411,15 @@ exit:
 void tipc_mon_peer_down(struct net *net, u32 addr, int bearer_id)
 {
        struct tipc_monitor *mon = tipc_monitor(net, bearer_id);
-       struct tipc_peer *self = get_self(net, bearer_id);
+       struct tipc_peer *self;
        struct tipc_peer *peer, *head;
        struct tipc_mon_domain *dom;
        int applied;
 
+       if (!mon)
+               return;
+
+       self = get_self(net, bearer_id);
        write_lock_bh(&mon->lock);
        peer = get_peer(mon, addr);
        if (!peer) {