[PATCH 3/6] media: pwc: Return queued buffers on start_streaming() failure

[Valery Borovsky <vebohr@gmail.com>]

The vb2 framework hands buffers to the driver via buf_queue() before
calling start_streaming().  If start_streaming() returns an error
without first returning those buffers via vb2_buffer_done(),
vb2_start_streaming() fires WARN_ON(owned_by_drv_count) and the queued
buffers leak.

pwc's start_streaming() had two early returns that hit this trap:
-ENODEV when the USB device was already disconnected, and -ERESTARTSYS
when mutex_lock_interruptible() was interrupted by a signal.  Call the
existing pwc_cleanup_queued_bufs() helper with VB2_BUF_STATE_QUEUED
before returning (matching the state already used by the
pwc_isoc_init() error path in the same function).

This mirrors the uvcvideo fix in commit 4cf3b6fd54eb ("media: uvcvideo:
Return queued buffers on start_streaming() failure").

Fixes: ceede9fa8939 ("[media] pwc: Fix locking")
Cc: stable@vger.kernel.org
Signed-off-by: Valery Borovsky <vebohr@gmail.com>
---
 drivers/media/usb/pwc/pwc-if.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/pwc/pwc-if.c b/drivers/media/usb/pwc/pwc-if.c
index c416e2fc5754..59b99ac8fcb6 100644
--- a/drivers/media/usb/pwc/pwc-if.c
+++ b/drivers/media/usb/pwc/pwc-if.c
@@ -710,11 +710,15 @@ static int start_streaming(struct vb2_queue *vq, unsigned int count)
 	struct pwc_device *pdev = vb2_get_drv_priv(vq);
 	int r;
 
-	if (!pdev->udev)
+	if (!pdev->udev) {
+		pwc_cleanup_queued_bufs(pdev, VB2_BUF_STATE_QUEUED);
 		return -ENODEV;
+	}
 
-	if (mutex_lock_interruptible(&pdev->v4l2_lock))
+	if (mutex_lock_interruptible(&pdev->v4l2_lock)) {
+		pwc_cleanup_queued_bufs(pdev, VB2_BUF_STATE_QUEUED);
 		return -ERESTARTSYS;
+	}
 	/* Turn on camera and set LEDS on */
 	pwc_camera_power(pdev, 1);
 	pwc_set_leds(pdev, leds[0], leds[1]);
-- 
2.51.0