[PATCH 4.19 022/267] RDMA/uverbs: Make the event_queue fds return POLLERR when disassociated

[Greg Kroah-Hartman]

From: Jason Gunthorpe <jgg@xxxxxxxxxxxx>

[ Upstream commit eb356e6dc15a30af604f052cd0e170450193c254 ]

If is_closed is set, and the event list is empty, then read() will return
-EIO without blocking. After setting is_closed in
ib_uverbs_free_event_queue(), we do trigger a wake_up on the poll_wait,
but the fops->poll() function does not check it, so poll will continue to
sleep on an empty list.

Fixes: 14e23bd6d221 ("RDMA/core: Fix locking in ib_uverbs_event_read")
Link: https://lore.kernel.org/r/0-v1-ace813388969+48859-uverbs_poll_fix%25jgg@xxxxxxxxxxxx
Reviewed-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/infiniband/core/uverbs_main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
index 5404717998b0..fc4b46258c75 100644
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -360,6 +360,8 @@ static __poll_t ib_uverbs_event_poll(struct ib_uverbs_event_queue *ev_queue,
 	spin_lock_irq(&ev_queue->lock);
 	if (!list_empty(&ev_queue->event_list))
 		pollflags = EPOLLIN | EPOLLRDNORM;
+	else if (ev_queue->is_closed)
+		pollflags = EPOLLERR;
 	spin_unlock_irq(&ev_queue->lock);
 
 	return pollflags;
-- 
2.25.1