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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>
This commit is contained in:
Ying Xue 2013-12-09 22:54:47 -08:00 committed by David S. Miller
parent 993b858e37
commit 00ede97709
1 changed files with 8 additions and 3 deletions
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11
net/tipc/handler.c
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@ -56,12 +56,13 @@ unsigned int tipc_k_signal(Handler routine, unsigned long argument)
{
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 @@ void tipc_handler_stop(void)
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);