[PATCH v4] media: ti: vpe: quiesce overflow recovery before freeing streams

[Fan Wu]

The VIP overflow recovery worker is armed from the hardirq handler when a
FIFO overflow is detected, and the list-complete path looks the stream up
through the VPDMA list private pointer. Both keep touching stream, port
and device state; the recovery worker also resets the parser and VPDMA,
repopulates the descriptor list, and re-enables the per-list IRQs.

vip_stop_streaming() masks and clears the per-list IRQs, but it neither
synchronizes the hardirq handler nor disables recovery_work. An overflow
IRQ that has already queued recovery_work, or a list-complete IRQ in
flight when the stream is torn down, can therefore still dereference the
stream after its resources are released: the descriptor list is freed by
vip_release_stream() on file release, and the stream itself by
free_stream() on unbind/remove.

Drain the recovery worker and the IRQ handler at both teardown points
through a shared vip_quiesce_stream() helper, before any stream-owned
resource is released. disable_work_sync() cancels pending recovery_work,
drains a running instance, and raises its disable depth, so a subsequent
schedule_work() issued by a racing IRQ handler is rejected at the
workqueue scheduler: recovery_work cannot be requeued after
disable_work_sync() takes effect. The worker may still re-enable the
per-list IRQs before disable_work_sync() returns; disable_irqs() then
masks those sources and synchronize_irq() waits for any in-flight handler
that still dereferences stream state. In vip_stop_streaming() the helper
runs before the parser is stopped, since a worker drained by
disable_work_sync() may re-enable the parser before exiting and would
otherwise undo the stop. recovery_work is created disabled and enabled in
vip_start_streaming() before IRQs, pairing the enable with the teardown
disable across the streaming lifecycle.

This issue was found by an in-house static analysis tool and confirmed
by manual code review.

Fixes: fc2873aa4a21 ("media: ti: vpe: Add the VIP driver")
Cc: stable@xxxxxxxxxxxxxxx
Assisted-by: Codex:gpt-5.6
Signed-off-by: Fan Wu <fanwu01@xxxxxxxxxx>
---
Changes in v4:
- Drop the unrelated vpdma_hwlist_release() cleanup from this fix (Hans
  Verkuil).
- In free_stream(), call vip_quiesce_stream() before clearing
  cap_streams[], so the stream remains published while in-flight IRQ
  handling is drained (Hans Verkuil).

Changes in v3:
- Replace the per-stream irq_rearm_allowed flag and the repeated IRQ
  disable/synchronize_irq() in vip_quiesce_stream() with the workqueue
  disable-depth API (disable_work_sync/enable_work/disable_work), as
  suggested by Yemike Abhilash Chandra. This also closes a window the v2
  double-drain left open, where its second synchronize_irq() waited for
  the in-flight handler but did not cancel the recovery_work it had
  requeued, so that work could run after free.
- Create recovery_work disabled and enable it in vip_start_streaming()
  before IRQs.
- In vip_stop_streaming(), quiesce before stopping the parser: a worker
  drained by disable_work_sync() may re-enable the parser before exiting,
  so stopping the parser first would be undone.

Changes in v2:
- Drain the overflow recovery worker at both teardown points through a
  shared vip_quiesce_stream() helper: vip_stop_streaming() (file release
  path) and free_stream() (unbind/remove). v1 drained only in
  free_stream().
- Document how the issue was found and that the patch was prepared with
  LLM assistance (Assisted-by trailer and body note).

Link: https://lore.kernel.org/r/20260708013738.110752-1-fanwu01@xxxxxxxxxx/
---
 drivers/media/platform/ti/vpe/vip.c | 37 +++++++++++++++++++++++++----
 1 file changed, 33 insertions(+), 4 deletions(-)

diff --git a/drivers/media/platform/ti/vpe/vip.c b/drivers/media/platform/ti/vpe/vip.c
index cb0a5a07a3d4..673f9addfade 100644
--- a/drivers/media/platform/ti/vpe/vip.c
+++ b/drivers/media/platform/ti/vpe/vip.c
@@ -814,6 +814,22 @@ static void clear_irqs(struct vip_dev *dev, int irq_num, int list_num)
 	vpdma_clear_list_stat(dev->shared->vpdma, irq_num, dev->slice_id);
 }
 
+/*
+ * Quiesce recovery work and per-list IRQs before releasing stream resources.
+ * disable_work_sync() prevents the overflow handler from requeueing recovery
+ * work. Mask and synchronize IRQs afterwards because a running worker may
+ * have re-enabled them before exiting.
+ */
+static void vip_quiesce_stream(struct vip_stream *stream)
+{
+	struct vip_dev *dev = stream->port->dev;
+
+	disable_work_sync(&stream->recovery_work);
+	disable_irqs(dev, dev->slice_id, stream->list_num);
+	clear_irqs(dev, dev->slice_id, stream->list_num);
+	synchronize_irq(dev->irq);
+}
+
 static void populate_desc_list(struct vip_stream *stream)
 {
 	struct vip_port *port = stream->port;
@@ -2428,6 +2444,7 @@ static int vip_start_streaming(struct vb2_queue *vq, unsigned int count)
 		goto err;
 
 	stream->num_recovery = 0;
+	enable_work(&stream->recovery_work);
 
 	clear_irqs(dev, dev->slice_id, stream->list_num);
 	enable_irqs(dev, dev->slice_id, stream->list_num);
@@ -2452,13 +2469,17 @@ static void vip_stop_streaming(struct vb2_queue *vq)
 	struct vip_dev *dev = port->dev;
 	int ret;
 
+	/*
+	 * A running recovery worker may re-enable the parser, so quiesce it
+	 * and its IRQ handler before stopping the parser or releasing the
+	 * descriptor list.
+	 */
+	vip_quiesce_stream(stream);
+
 	vip_parser_stop_imm(port, true);
 	vip_enable_parser(port, false);
 	unset_fmt_params(stream);
 
-	disable_irqs(dev, dev->slice_id, stream->list_num);
-	clear_irqs(dev, dev->slice_id, stream->list_num);
-
 	if (port->subdev) {
 		ret = v4l2_subdev_call(port->subdev, video, s_stream, 0);
 		if (ret)
@@ -3074,6 +3095,8 @@ static int alloc_stream(struct vip_port *port, int stream_id, int vfl_type)
 		goto do_free_hwlist;
 
 	INIT_WORK(&stream->recovery_work, vip_overflow_recovery_work);
+	/* Start disabled; vip_start_streaming() enables it before IRQs. */
+	disable_work(&stream->recovery_work);
 
 	INIT_LIST_HEAD(&stream->vidq);
 
@@ -3139,6 +3162,13 @@ static void free_stream(struct vip_stream *stream)
 		return;
 
 	dev = stream->port->dev;
+	/*
+	 * Quiesce the IRQ handler and recovery worker, then drop the stream
+	 * from cap_streams[], before releasing stream-owned resources.
+	 */
+	vip_quiesce_stream(stream);
+	stream->port->cap_streams[stream->stream_id] = NULL;
+
 	/* Free up the Drop queue */
 	list_for_each_safe(pos, q, &stream->dropq) {
 		buf = list_entry(pos,
@@ -3150,7 +3180,6 @@ static void free_stream(struct vip_stream *stream)
 
 	video_unregister_device(stream->vfd);
 	vpdma_hwlist_release(dev->shared->vpdma, stream->list_num);
-	stream->port->cap_streams[stream->stream_id] = NULL;
 	kfree(stream);
 }
 
-- 
2.34.1