[PATCH v1 1/5] ALSA: virtio: Notify queued PCM messages after send errors

[Joonho Lee <mynameisjune111@gmail.com>]

virtsnd_pcm_msg_send() advances a message length before adding it to
the virtqueue. If a later add fails, the error path returns without
restoring that length or notifying the device about earlier messages
added by the same call. The device can therefore leave successfully
queued messages unprocessed, while the failed message appears
already submitted.

Restore the failed message's length increment and notify the device
about any earlier messages added by this call before returning the
error. Keep the polling feature path unchanged.

Fixes: fe981e67568c ("ALSA: virtio: use ack callback")
Assisted-by: LLM
Signed-off-by: Joonho Lee <mynameisjune111@gmail.com>
---
Validation: source-extracted ASan/UBSan partial-enqueue and polling
checks; included in the W=1 builds through patches 3 and 5. This commit
was not separately kernel-built.

 sound/virtio/virtio_pcm_msg.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/sound/virtio/virtio_pcm_msg.c b/sound/virtio/virtio_pcm_msg.c
index 72103f606716..5371f4985fd0 100644
--- a/sound/virtio/virtio_pcm_msg.c
+++ b/sound/virtio/virtio_pcm_msg.c
@@ -260,6 +260,18 @@ int virtsnd_pcm_msg_send(struct virtio_pcm_substream *vss, unsigned long offset,
 				dev_err(&vdev->dev,
 					"SID %u: failed to send I/O message\n",
 					vss->sid);
+				msg->length -= n;
+
+				/*
+				 * Do not leave earlier messages queued without notifying
+				 * the device when a later message could not be added.
+				 */
+				if (msg_count != vss->msg_count &&
+				    !(vss->features &
+				      (1U << VIRTIO_SND_PCM_F_MSG_POLLING)) &&
+				    virtqueue_kick_prepare(vqueue))
+					virtqueue_notify(vqueue);
+
 				return rc;
 			}
 
-- 
2.54.0 (Apple Git-157)