media: vb2: Return queued buffers from start_streaming() on error

The vb2 framework hands buffer ownership 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 != 0) and the queued buffers leak.

This was previously fixed for uvcvideo in commit 4cf3b6fd54eb ("media:
uvcvideo: Return queued buffers on start_streaming() failure"). The same pattern exists in six sibling drivers that still return an errno early (USB disconnect, signal-interrupted mutex, or media-graph / format lookup failure) without draining their internal queued-buffer list. Each patch reuses or extends the helper / cleanup label that the driver's other error paths already use.

airspy.c - moves mutex_lock above the !s->udev check and
jumps to the existing err_clear_bit label, which already drains s->queued_bufs.
msi2500.c - rebuilds start_streaming into a goto chain that
drains the queue on every failure (including previously-masked set_usb_adc / ctrl_msg paths); parameterizes msi2500_cleanup_queued_bufs() with vb2_buffer_state so the start_streaming path passes _QUEUED. Rolls back isoc_init via msi2500_isoc_cleanup() on ctrl_msg failure.
pwc-if.c - calls pwc_cleanup_queued_bufs(.., _QUEUED) before
each early return; state matches the existing pwc_isoc_init() error-path in the same function.
rtl2832_sdr.c - calls rtl2832_sdr_cleanup_queued_bufs() before
each early return and at the err label. Adds an explicit success return so the cleanup at err no longer runs on the success path. Parameterizes the helper with vb2_buffer_state.
dcmipp-bytecap.c - replaces the bare -EINVAL return for failed
subdev lookup with a goto err_buffer_done.
sun4i_dma.c - replaces the bare -EINVAL return for failed
csi-format lookup with a goto err_clear_dma_queue.

These sites were located by a Coccinelle pattern that matches return -ERRNO inside a start_streaming(struct vb2_queue *, unsigned int) callback without a preceding vb2_buffer_done() on the same path.

Build-tested with drivers/media/ allmodconfig. Not runtime-tested on any of the six devices. Maintainers with hardware are kindly asked to verify nothing regresses on their device.

Valery Borovsky (6):
media: airspy: Return queued buffers on start_streaming() failure
media: msi2500: Return queued buffers on start_streaming() failure
media: pwc: Return queued buffers on start_streaming() failure
media: rtl2832_sdr: Return queued buffers on start_streaming() failure
media: stm32-dcmipp: Return queued buffers on start_streaming()
failure
media: sun4i-csi: Return queued buffers on start_streaming() failure

 drivers/media/dvb-frontends/rtl2832_sdr.c     | 19 ++++++++---
 .../st/stm32/stm32-dcmipp/dcmipp-bytecap.c    |  6 ++--
 .../platform/sunxi/sun4i-csi/sun4i_dma.c      |  6 ++--
 drivers/media/usb/airspy/airspy.c             |  8 +++--
 drivers/media/usb/msi2500/msi2500.c           | 32 ++++++++++++++-----
 drivers/media/usb/pwc/pwc-if.c                |  8 +++--
 6 files changed, 57 insertions(+), 22 deletions(-)

2.51.0

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.

airspy_start_streaming() returned -ENODEV early when the USB device had been disconnected (s->udev == NULL) without returning any buffers that buf_queue() had already accepted. Take v4l2_lock first and jump to the existing err_clear_bit label, which already drains s->queued_bufs via vb2_buffer_done(..., VB2_BUF_STATE_QUEUED) before unlocking.

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

---
 drivers/media/usb/airspy/airspy.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

index 8f6b721ba107..57edb42463e8 100644
@@ -522,11 +522,13 @@ static int airspy_start_streaming(struct vb2_queue *vq, unsigned int count)
 
 	dev_dbg(s->dev, "\n");
 
-	if (!s->udev)
-		return -ENODEV;
-
 	mutex_lock(&s->v4l2_lock);
 
+	if (!s->udev) {
+		ret = -ENODEV;
+		goto err_clear_bit;
+	}
+
 	s->sequence = 0;
 
 	set_bit(POWER_ON, &s->flags);

2.51.0

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.

msi2500_start_streaming() had five error paths that all hit this trap and were further tangled by ret-overwriting between calls:

- -ENODEV when the USB device was already disconnected
- -ERESTARTSYS when mutex_lock_interruptible() was interrupted
- msi2500_set_usb_adc() failure: ret was silently overwritten by the next call (msi2500_isoc_init), so the error was lost entirely
- msi2500_isoc_init() failure: cleanup_queued_bufs was called, but the function then fell through to msi2500_ctrl_msg() and again masked the original error by overwriting ret
- msi2500_ctrl_msg(CMD_START_STREAMING) failure: no cleanup at all, leaving isoc URBs submitted with no way for the driver to consume them

Consolidate the error paths into a small goto chain. Every failure now stops the function, drains the queued-buffer list, and returns the real error code. The ctrl_msg failure path also rolls back the preceding msi2500_isoc_init() via msi2500_isoc_cleanup() before unlocking and draining.

The cleanup helper takes a vb2_buffer_state argument so that the start_streaming error paths can pass VB2_BUF_STATE_QUEUED (as expected by userspace on start_streaming failure) while stop_streaming keeps its existing VB2_BUF_STATE_ERROR semantics.

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

---
 drivers/media/usb/msi2500/msi2500.c | 32 +++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

index 1ff98956b680..0614087c3c3c 100644
@@ -541,7 +541,8 @@ static int msi2500_isoc_init(struct msi2500_dev *dev)
 }
 
 /* Must be called with vb_queue_lock hold */
-static void msi2500_cleanup_queued_bufs(struct msi2500_dev *dev)
+static void msi2500_cleanup_queued_bufs(struct msi2500_dev *dev,
+					enum vb2_buffer_state state)
 {
 	unsigned long flags;
 

@@ -554,7 +555,7 @@ static void msi2500_cleanup_queued_bufs(struct msi2500_dev *dev)
 		buf = list_entry(dev->queued_bufs.next,
 				 struct msi2500_frame_buf, list);
 		list_del(&buf->list);
-		vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_ERROR);
+		vb2_buffer_done(&buf->vb.vb2_buf, state);
 	}
 	spin_unlock_irqrestore(&dev->queued_bufs_lock, flags);
 }

@@ -830,25 +831,40 @@ static int msi2500_start_streaming(struct vb2_queue *vq, unsigned int count)
 
 	dev_dbg(dev->dev, "\n");
 
-	if (!dev->udev)
-		return -ENODEV;
+	if (!dev->udev) {
+		ret = -ENODEV;
+		goto err_cleanup;
+	}
 
-	if (mutex_lock_interruptible(&dev->v4l2_lock))
-		return -ERESTARTSYS;
+	if (mutex_lock_interruptible(&dev->v4l2_lock)) {
+		ret = -ERESTARTSYS;
+		goto err_cleanup;
+	}
 
 	/* wake-up tuner */
 	v4l2_subdev_call(dev->v4l2_subdev, core, s_power, 1);
 
 	ret = msi2500_set_usb_adc(dev);
+	if (ret)
+		goto err_unlock_cleanup;
 
 	ret = msi2500_isoc_init(dev);
 	if (ret)
-		msi2500_cleanup_queued_bufs(dev);
+		goto err_unlock_cleanup;
 
 	ret = msi2500_ctrl_msg(dev, CMD_START_STREAMING, 0);
+	if (ret)
+		goto err_isoc_cleanup;
 
 	mutex_unlock(&dev->v4l2_lock);
+	return 0;
 
+err_isoc_cleanup:
+	msi2500_isoc_cleanup(dev);
+err_unlock_cleanup:
+	mutex_unlock(&dev->v4l2_lock);
+err_cleanup:
+	msi2500_cleanup_queued_bufs(dev, VB2_BUF_STATE_QUEUED);
 	return ret;
 }
 

@@ -863,7 +879,7 @@ static void msi2500_stop_streaming(struct vb2_queue *vq)
 	if (dev->udev)
 		msi2500_isoc_cleanup(dev);
 
-	msi2500_cleanup_queued_bufs(dev);
+	msi2500_cleanup_queued_bufs(dev, VB2_BUF_STATE_ERROR);
 
 	/* according to tests, at least 700us delay is required  */
 	msleep(20);

2.51.0

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").

---
 drivers/media/usb/pwc/pwc-if.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

index c416e2fc5754..59b99ac8fcb6 100644
@@ -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

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.

rtl2832_sdr_start_streaming() had multiple error paths that hit this
trap: two direct early returns (-ENODEV, -ERESTARTSYS), plus six goto err paths covering subdev s_power, tuner setup, ADC setup, stream-buffer allocation, urb allocation, and urb submission failures. None of them returned the queued buffers.

The original function had no distinct success exit and fell straight through into the err label, which previously only did mutex_unlock and "return ret". Adding queued-buffer cleanup at err must therefore be paired with an explicit success return; otherwise every successful start would also drain the buffer queue and kill streaming. Add that success return, then add rtl2832_sdr_cleanup_queued_bufs() at the err label and before each early return.

The cleanup helper takes a vb2_buffer_state argument so that the start_streaming error paths can pass VB2_BUF_STATE_QUEUED (as expected by userspace on start_streaming failure) while stop_streaming keeps its existing VB2_BUF_STATE_ERROR semantics.

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

The err label still does not roll back power_ctrl(), frontend_ctrl(), the POWER_ON flag, or stream/URB allocations that may have happened before the failing step. Those are pre-existing leaks of a different class and are not addressed here.

---
 drivers/media/dvb-frontends/rtl2832_sdr.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

index 422d1a7b5456..c564485e3bbb 100644
@@ -399,7 +399,8 @@ static int rtl2832_sdr_alloc_urbs(struct rtl2832_sdr_dev *dev)
 }
 
 /* Must be called with vb_queue_lock hold */
-static void rtl2832_sdr_cleanup_queued_bufs(struct rtl2832_sdr_dev *dev)
+static void rtl2832_sdr_cleanup_queued_bufs(struct rtl2832_sdr_dev *dev,
+					    enum vb2_buffer_state state)
 {
 	struct platform_device *pdev = dev->pdev;
 	unsigned long flags;

@@ -413,7 +414,7 @@ static void rtl2832_sdr_cleanup_queued_bufs(struct rtl2832_sdr_dev *dev)
 		buf = list_entry(dev->queued_bufs.next,
 				struct rtl2832_sdr_frame_buf, list);
 		list_del(&buf->list);
-		vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_ERROR);
+		vb2_buffer_done(&buf->vb.vb2_buf, state);
 	}
 	spin_unlock_irqrestore(&dev->queued_bufs_lock, flags);
 }

@@ -855,11 +856,15 @@ static int rtl2832_sdr_start_streaming(struct vb2_queue *vq, unsigned int count)
 
 	dev_dbg(&pdev->dev, "\n");
 
-	if (!dev->udev)
+	if (!dev->udev) {
+		rtl2832_sdr_cleanup_queued_bufs(dev, VB2_BUF_STATE_QUEUED);
 		return -ENODEV;
+	}
 
-	if (mutex_lock_interruptible(&dev->v4l2_lock))
+	if (mutex_lock_interruptible(&dev->v4l2_lock)) {
+		rtl2832_sdr_cleanup_queued_bufs(dev, VB2_BUF_STATE_QUEUED);
 		return -ERESTARTSYS;
+	}
 
 	if (d->props->power_ctrl)
 		d->props->power_ctrl(d, 1);

@@ -900,7 +905,11 @@ static int rtl2832_sdr_start_streaming(struct vb2_queue *vq, unsigned int count)
 	if (ret)
 		goto err;
 
+	mutex_unlock(&dev->v4l2_lock);
+	return 0;
+
 err:
+	rtl2832_sdr_cleanup_queued_bufs(dev, VB2_BUF_STATE_QUEUED);
 	mutex_unlock(&dev->v4l2_lock);
 
 	return ret;

@@ -920,7 +929,7 @@ static void rtl2832_sdr_stop_streaming(struct vb2_queue *vq)
 	rtl2832_sdr_kill_urbs(dev);
 	rtl2832_sdr_free_urbs(dev);
 	rtl2832_sdr_free_stream_bufs(dev);
-	rtl2832_sdr_cleanup_queued_bufs(dev);
+	rtl2832_sdr_cleanup_queued_bufs(dev, VB2_BUF_STATE_ERROR);
 	rtl2832_sdr_unset_adc(dev);
 
 	/* sleep tuner */

2.51.0

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.

dcmipp_bytecap_start_streaming() returned -EINVAL when the source subdevice could not be resolved from the media graph, before pm_runtime_resume_and_get() and media_pipeline_start() had been called. The remaining error paths already converge on the err_buffer_done label, which calls dcmipp_bytecap_all_buffers_done(..., VB2_BUF_STATE_QUEUED). Jump to that label directly: the intermediate err_pm_put / err_media_pipeline_stop labels are skipped, which is correct because nothing they would undo has happened yet.

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

---
 .../media/platform/st/stm32/stm32-dcmipp/dcmipp-bytecap.c   | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

index a42f43d19f9e..f0e809458489 100644
@@ -401,8 +401,10 @@ static int dcmipp_bytecap_start_streaming(struct vb2_queue *vq,
 	 */
 	if (!vcap->s_subdev) {
 		pad = media_pad_remote_pad_first(&vcap->vdev.entity.pads[0]);
-		if (!pad || !is_media_entity_v4l2_subdev(pad->entity))
-			return -EINVAL;
+		if (!pad || !is_media_entity_v4l2_subdev(pad->entity)) {
+			ret = -EINVAL;
+			goto err_buffer_done;
+		}
 		vcap->s_subdev = media_entity_to_v4l2_subdev(pad->entity);
 		vcap->s_subdev_pad_nb = pad->index;
 	}

2.51.0

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.

sun4i_csi_start_streaming() returned -EINVAL when no matching CSI format could be found, before any setup (scratch buffer allocation, pipeline start) had been performed. The remaining error paths already converge on the err_clear_dma_queue label, which calls return_all_buffers(..., VB2_BUF_STATE_QUEUED) under csi->qlock. Jump to that label directly: the intermediate err_disable_device / err_disable_pipeline / err_free_scratch_buffer labels are skipped, which is correct because nothing they would undo has happened yet.

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

---
 drivers/media/platform/sunxi/sun4i-csi/sun4i_dma.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

index e911c7f7acc5..4781db21c205 100644
@@ -234,8 +234,10 @@ static int sun4i_csi_start_streaming(struct vb2_queue *vq, unsigned int count)
 	int ret;
 
 	csi_fmt = sun4i_csi_find_format(&csi->fmt.pixelformat, NULL);
-	if (!csi_fmt)
-		return -EINVAL;
+	if (!csi_fmt) {
+		ret = -EINVAL;
+		goto err_clear_dma_queue;
+	}
 
 	dev_dbg(csi->dev, "Starting capture\n");
 

2.51.0