[PATCH v2 3/4] ALSA: compress: add missing OPEN-state gate to SET_METADATA

[Peter Ujfalusi <peter.ujfalusi@linux.intel.com>]

snd_compr_set_metadata() calls stream->ops->set_metadata() straight
after copy_from_user(), without ever checking runtime->state, even
though the function's own comment says a parameter change should only
be allowed once the stream has left the OPEN state. Every other
metadata/param entry point in this file (SET_PARAMS, WRITE, ...)
enforces that gate.

A codec driver's set_metadata callback can assume SET_PARAMS has
already run and initialised its private state; calling it while the
stream is still OPEN can operate on that uninitialised state.

Add the OPEN-state check the existing comment already documents.

Fixes: 9727b490e543 ("ALSA: compress: add support for gapless playback")
Cc: stable@vger.kernel.org
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Acked-by: Vinod Koul <vkoul@kernel.org>
---
 sound/core/compress_offload.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
index d6863336f21c..a250c6b53996 100644
--- a/sound/core/compress_offload.c
+++ b/sound/core/compress_offload.c
@@ -789,6 +789,9 @@ snd_compr_set_metadata(struct snd_compr_stream *stream, unsigned long arg)
 	* we should allow parameter change only when stream has been
 	* opened not in other cases
 	*/
+	if (stream->runtime->state == SNDRV_PCM_STATE_OPEN)
+		return -EBADFD;
+
 	if (copy_from_user(&metadata, (void __user *)arg, sizeof(metadata)))
 		return -EFAULT;
 
-- 
2.56.0