On Wed, 29 Sep 2021 13:36:20 +0200,
John Keeping wrote:
>
> If the sequencer device outlives the rawmidi device, then
> snd_rawmidi_dev_seq_free() will run after release_rawmidi_device() has
> freed the snd_rawmidi structure.
>
> This can easily be reproduced with CONFIG_DEBUG_KOBJECT_RELEASE.
>
> Keep a reference to the rawmidi device until the sequencer has been
> destroyed in order to avoid this.
>
> Signed-off-by: John Keeping <john@xxxxxxxxxxxx>
Thanks for the patch. I wonder, though, how this could be triggered.
Is this the case where the connected sequencer device is being used
while the sound card gets released? Or is it something else?
thanks,
Takashi
> ---
> sound/core/rawmidi.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c
> index 6f30231bdb88..b015f5f69175 100644
> --- a/sound/core/rawmidi.c
> +++ b/sound/core/rawmidi.c
> @@ -1860,6 +1860,7 @@ static void snd_rawmidi_dev_seq_free(struct snd_seq_device *device)
> struct snd_rawmidi *rmidi = device->private_data;
>
> rmidi->seq_dev = NULL;
> + put_device(&rmidi->dev);
> }
> #endif
>
> @@ -1936,6 +1937,9 @@ static int snd_rawmidi_dev_register(struct snd_device *device)
> #if IS_ENABLED(CONFIG_SND_SEQUENCER)
> if (!rmidi->ops || !rmidi->ops->dev_register) { /* own registration mechanism */
> if (snd_seq_device_new(rmidi->card, rmidi->device, SNDRV_SEQ_DEV_ID_MIDISYNTH, 0, &rmidi->seq_dev) >= 0) {
> + /* Ensure we outlive the sequencer (see snd_rawmidi_dev_seq_free). */
> + get_device(&rmidi->dev);
> +
> rmidi->seq_dev->private_data = rmidi;
> rmidi->seq_dev->private_free = snd_rawmidi_dev_seq_free;
> sprintf(rmidi->seq_dev->name, "MIDI %d-%d", rmidi->card->number, rmidi->device);
> --
> 2.33.0
>
