During encoder processing, there is a case where the IRQ response could
return the buffer back to userspace via v4l2_m2m_buf_done call. In this
time, userspace could queue up this same buffer before start_encode removes
the index from the ready queue. This would then lead to a case where the
buffer in the ready queue could be a self loop due to the
WRITE_ONCE(prev->next, new) call in __list_add.

When __list_del is finally called, the loop is already made so nothing
points back to ready queue list head and pointers are poisoned.

A buffer should not be marked as DONE before the buffer is removed from
m2m ready queue. Move removal entirely to finish_encode.

Signed-off-by: Brandon Brnich <b-brnich@ti.com>
---

V2:
 - Update function to use reported index from encoder
 - Fix reported media CI bot style errors with brackets

 .../chips-media/wave5/wave5-vpu-enc.c         | 29 +++----------------
 1 file changed, 4 insertions(+), 25 deletions(-)

diff --git a/drivers/media/platform/chips-media/wave5/wave5-vpu-enc.c b/drivers/media/platform/chips-media/wave5/wave5-vpu-enc.c
index 7613fcdbafed..c605a91718d8 100644
--- a/drivers/media/platform/chips-media/wave5/wave5-vpu-enc.c
+++ b/drivers/media/platform/chips-media/wave5/wave5-vpu-enc.c
@@ -226,13 +226,6 @@ static int start_encode(struct vpu_instance *inst, u32 *fail_res)
 	} else {
 		dev_dbg(inst->dev->dev, "%s: wave5_vpu_enc_start_one_frame success\n",
 			__func__);
-		/*
-		 * Remove the source buffer from the ready-queue now and finish
-		 * it in the videobuf2 framework once the index is returned by the
-		 * firmware in finish_encode
-		 */
-		if (src_buf)
-			v4l2_m2m_src_buf_remove_by_idx(m2m_ctx, src_buf->vb2_buf.index);
 	}
 
 	return 0;
@@ -259,27 +252,13 @@ static void wave5_vpu_enc_finish_encode(struct vpu_instance *inst)
 		__func__,  enc_output_info.pic_type, enc_output_info.recon_frame_index,
 		enc_output_info.enc_src_idx, enc_output_info.enc_pic_byte, enc_output_info.pts);
 
-	/*
-	 * The source buffer will not be found in the ready-queue as it has been
-	 * dropped after sending of the encode firmware command, locate it in
-	 * the videobuf2 queue directly
-	 */
 	if (enc_output_info.enc_src_idx >= 0) {
-		struct vb2_buffer *vb = vb2_get_buffer(v4l2_m2m_get_src_vq(m2m_ctx),
-						       enc_output_info.enc_src_idx);
-		if (vb->state != VB2_BUF_STATE_ACTIVE)
-			dev_warn(inst->dev->dev,
-				 "%s: encoded buffer (%d) was not in ready queue %i.",
-				 __func__, enc_output_info.enc_src_idx, vb->state);
-		else
-			src_buf = to_vb2_v4l2_buffer(vb);
-
-		if (src_buf) {
+		src_buf = v4l2_m2m_src_buf_remove_by_idx(m2m_ctx, enc_output_info.enc_src_idx);
+		if (!src_buf) {
+			dev_warn(inst->dev->dev, "%s: no source buffer found\n", __func__);
+		} else {
 			inst->timestamp = src_buf->vb2_buf.timestamp;
 			v4l2_m2m_buf_done(src_buf, VB2_BUF_STATE_DONE);
-		} else {
-			dev_warn(inst->dev->dev, "%s: no source buffer with index: %d found\n",
-				 __func__, enc_output_info.enc_src_idx);
 		}
 	}
 
-- 
2.43.0