[PATCH 0/2] ALSA: compress: Robustness improvements in pointer() handling

[PATCH 0/2] ALSA: compress: Robustness improvements in pointer() handling

[Mark Brown]

While looking at an ASoC driver I happened to notice a divide by zero on
a pointer operation, discussion of which with Péter Ujfalusi identified
several other issues in the handling of pointer operations in the core.
This isn't a comprehensive review, it's just fixing up issues that
happened to be noticed.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
Mark Brown (2):
      ALSA: compress: Refuse to update timestamps for unconfigured streams
      ALSA: compress: Pay attention if drivers error out retrieving pointers

 sound/core/compress_offload.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)
---
base-commit: 7aaa8047eafd0bd628065b15757d9b48c5f9c07d
change-id: 20260330-alsa-unconfigured-tstamp-6886ed04cf22

Best regards,
--  
Mark Brown <broonie@kernel.org>

[PATCH 1/2] ALSA: compress: Refuse to update timestamps for unconfigured streams

[Mark Brown]

There are a number of mechanisms, including the userspace accessible
timestamp and buffer availability ioctl()s, which allow us to trigger
a timestamp update on a stream before it has been configured. Since
drivers might rely on stream configuration for reporting of pcm_io_frames,
including potentially doing a division by the number of channels, and
these operations are not meaningful for an unconfigured stream reject
attempts to read timestamps before any configuration is done.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 sound/core/compress_offload.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
index fdba6e4b25fd..67b3b1a3b526 100644
--- a/sound/core/compress_offload.c
+++ b/sound/core/compress_offload.c
@@ -192,6 +192,14 @@ static int snd_compr_update_tstamp(struct snd_compr_stream *stream,
 {
 	if (!stream->ops->pointer)
 		return -ENOTSUPP;
+
+	switch (stream->runtime->state) {
+	case SNDRV_PCM_STATE_OPEN:
+		return -EBADFD;
+	default:
+		break;
+	}
+
 	stream->ops->pointer(stream, tstamp);
 	pr_debug("dsp consumed till %u total %llu bytes\n", tstamp->byte_offset,
 		 tstamp->copied_total);

-- 
2.47.3

[PATCH 2/2] ALSA: compress: Pay attention if drivers error out retrieving pointers

[Mark Brown]

Currently we have a return code on the driver pointer operation but the
core ignores that. Let's start paying attention.

Reported-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 sound/core/compress_offload.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
index 67b3b1a3b526..c91547451311 100644
--- a/sound/core/compress_offload.c
+++ b/sound/core/compress_offload.c
@@ -190,6 +190,8 @@ snd_compr_tstamp32_from_64(struct snd_compr_tstamp *tstamp32,
 static int snd_compr_update_tstamp(struct snd_compr_stream *stream,
 				   struct snd_compr_tstamp64 *tstamp)
 {
+	int ret;
+
 	if (!stream->ops->pointer)
 		return -ENOTSUPP;
 
@@ -200,7 +202,9 @@ static int snd_compr_update_tstamp(struct snd_compr_stream *stream,
 		break;
 	}
 
-	stream->ops->pointer(stream, tstamp);
+	ret = stream->ops->pointer(stream, tstamp);
+	if (ret != 0)
+		return ret;
 	pr_debug("dsp consumed till %u total %llu bytes\n", tstamp->byte_offset,
 		 tstamp->copied_total);
 	if (stream->direction == SND_COMPRESS_PLAYBACK)

-- 
2.47.3

Re: [PATCH 0/2] ALSA: compress: Robustness improvements in pointer() handling

[Vinod Koul]

On 01-04-26, 17:57, Mark Brown wrote:
> While looking at an ASoC driver I happened to notice a divide by zero on
> a pointer operation, discussion of which with Péter Ujfalusi identified
> several other issues in the handling of pointer operations in the core.
> This isn't a comprehensive review, it's just fixing up issues that
> happened to be noticed.
> 

Acked-by: Vinod Koul <vkoul@kernel.org>


-- 
~Vinod

Re: [PATCH 0/2] ALSA: compress: Robustness improvements in pointer() handling

[Takashi Iwai]

On Wed, 01 Apr 2026 18:57:33 +0200,
Mark Brown wrote:
> 
> While looking at an ASoC driver I happened to notice a divide by zero on
> a pointer operation, discussion of which with Péter Ujfalusi identified
> several other issues in the handling of pointer operations in the core.
> This isn't a comprehensive review, it's just fixing up issues that
> happened to be noticed.
> 
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---
> Mark Brown (2):
>       ALSA: compress: Refuse to update timestamps for unconfigured streams
>       ALSA: compress: Pay attention if drivers error out retrieving pointers

As it's at a quite late stage, I applied to for-next branch for 7.1.


thanks,

Takashi