linux-kernel - [PATCH 5.18 0376/1095] media: v4l2-mem2mem: prevent pollerr when last_buffer

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Date:   Mon, 15 Aug 2022 19:56:15 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ming Qian <ming.qian@....com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.18 0376/1095] media: v4l2-mem2mem: prevent pollerr when last_buffer_dequeued is set

From: Ming Qian <ming.qian@....com>

[ Upstream commit d4de27a9b1eadd33a2e40de87a646d1bf5fef756 ]

If the last buffer was dequeued from the capture queue,
signal userspace. DQBUF(CAPTURE) will return -EPIPE.

But if output queue is empty and capture queue is empty,
v4l2_m2m_poll_for_data will return EPOLLERR,
This is very easy to happen in drain.

When last_buffer_dequeued is set, we shouldn't return EPOLLERR,
but return EPOLLIN | EPOLLRDNORM.

Fixes: 1698a7f151126 ("media: v4l2-mem2mem: simplify poll logic")
Signed-off-by: Ming Qian <ming.qian@....com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@...all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/media/v4l2-core/v4l2-mem2mem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/v4l2-core/v4l2-mem2mem.c b/drivers/media/v4l2-core/v4l2-mem2mem.c
index 675e22895ebe..094e1815209b 100644
--- a/drivers/media/v4l2-core/v4l2-mem2mem.c
+++ b/drivers/media/v4l2-core/v4l2-mem2mem.c
@@ -924,7 +924,7 @@ static __poll_t v4l2_m2m_poll_for_data(struct file *file,
 	if ((!src_q->streaming || src_q->error ||
 	     list_empty(&src_q->queued_list)) &&
 	    (!dst_q->streaming || dst_q->error ||
-	     list_empty(&dst_q->queued_list)))
+	     (list_empty(&dst_q->queued_list) && !dst_q->last_buffer_dequeued)))
 		return EPOLLERR;
 
 	spin_lock_irqsave(&src_q->done_lock, flags);
-- 
2.35.1