tipc: protect handler_enabled variable with qitem_lock spin lock
'handler_enabled' is a global flag indicating whether the TIPC
signal handling service is enabled or not. The lack of lock
protection for this flag incurs a risk for contention, so that
a tipc_k_signal() call might queue a signal handler to a destroyed
signal queue, with unpredictable results. To correct this, we let
the already existing 'qitem_lock' protect the flag, as it already
does with the queue itself. This way, we ensure that the flag
always is consistent across all cores.
Signed-off-by: Ying Xue <ying.xue@windriver.com>
Reviewed-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/tipc/handler.c b/net/tipc/handler.c
index b36f0fc..e4bc8a2 100644
--- a/net/tipc/handler.c
+++ b/net/tipc/handler.c
@@ -56,12 +56,13 @@
{
struct queue_item *item;
+ spin_lock_bh(&qitem_lock);
if (!handler_enabled) {
pr_err("Signal request ignored by handler\n");
+ spin_unlock_bh(&qitem_lock);
return -ENOPROTOOPT;
}
- spin_lock_bh(&qitem_lock);
item = kmem_cache_alloc(tipc_queue_item_cache, GFP_ATOMIC);
if (!item) {
pr_err("Signal queue out of memory\n");
@@ -112,10 +113,14 @@
struct list_head *l, *n;
struct queue_item *item;
- if (!handler_enabled)
+ spin_lock_bh(&qitem_lock);
+ if (!handler_enabled) {
+ spin_unlock_bh(&qitem_lock);
return;
-
+ }
handler_enabled = 0;
+ spin_unlock_bh(&qitem_lock);
+
tasklet_kill(&tipc_tasklet);
spin_lock_bh(&qitem_lock);