IB/umad: Return EPOLLERR in case of when device disassociated

Currently, polling a umad device will always works, even if the device
was disassociated. Hence, returning EPOLLERR if device was
disassociated.

Fixes: 1da177e ("Linux-2.6.12-rc2")
Signed-off-by: Shay Drory <[email protected]>
Signed-off-by: Leon Romanovsky <[email protected]>

Author: shayshyi

drivers/infiniband/core/user_mad.c

@@ -653,10 +653,14 @@ static __poll_t ib_umad_poll(struct file *filp, struct poll_table_struct *wait)
 	/* we will always be able to post a MAD send */
 	__poll_t mask = EPOLLOUT | EPOLLWRNORM;
 
+	mutex_lock(&file->mutex);
 	poll_wait(filp, &file->recv_wait, wait);
 
 	if (!list_empty(&file->recv_list))
 		mask |= EPOLLIN | EPOLLRDNORM;
+	if (file->agents_dead)
+		mask = EPOLLERR;
+	mutex_unlock(&file->mutex);
 
 	return mask;
 }