[S390] 3270: fix race with stack local wait_queue_head_t.

A wait_event call with a stack local wait_queue_head_t structure that is
used to do the wake up for the wait_event is inherently racy. After the
wait_event finished the wake_up call might not have completed yet.
Remove the stack local wait_queue_head_t from raw3270_start_init and
use the global raw3270_wait_queue instead.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 4 insertions, 5 deletions

diff --git a/drivers/s390/char/raw3270.c b/drivers/s390/char/raw3270.c
index 0d98f1ff2edd..848ef7e8523f 100644
--- a/drivers/s390/char/raw3270.c
+++ b/drivers/s390/char/raw3270.c
@@ -549,7 +549,6 @@ raw3270_start_init(struct raw3270 *rp, struct raw3270_view *view,
                    struct raw3270_request *rq)
 {
         unsigned long flags;
-        wait_queue_head_t wq;
         int rc;
 
 #ifdef CONFIG_TN3270_CONSOLE
@@ -566,20 +565,20 @@ raw3270_start_init(struct raw3270 *rp, struct raw3270_view *view,
                 return rq->rc;
         }
 #endif
-        init_waitqueue_head(&wq);
         rq->callback = raw3270_wake_init;
-        rq->callback_data = &wq;
+        rq->callback_data = &raw3270_wait_queue;
         spin_lock_irqsave(get_ccwdev_lock(view->dev->cdev), flags);
         rc = __raw3270_start(rp, view, rq);
         spin_unlock_irqrestore(get_ccwdev_lock(view->dev->cdev), flags);
         if (rc)
                 return rc;
         /* Now wait for the completion. */
-        rc = wait_event_interruptible(wq, raw3270_request_final(rq));
+        rc = wait_event_interruptible(raw3270_wait_queue,
+                                      raw3270_request_final(rq));
         if (rc == -ERESTARTSYS) {       /* Interrupted by a signal. */
                 raw3270_halt_io(view->dev, rq);
                 /* No wait for the halt to complete. */
-                wait_event(wq, raw3270_request_final(rq));
+                wait_event(raw3270_wait_queue, raw3270_request_final(rq));
                 return -ERESTARTSYS;
         }
         return rq->rc;