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ALSA: timer: Handle userspace-driven timer ioctls from 32-bit tasks

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32-bit tasks on a 64-bit kernel can't use userspace-driven timers. The
compat handler for /dev/snd/timer doesn't list SNDRV_TIMER_IOCTL_CREATE,
so creating a timer fails with -ENOTTY. The file returned for a timer
has no .compat_ioctl either, so SNDRV_TIMER_IOCTL_TRIGGER fails with
-ENOTTY too.

struct snd_timer_uinfo has the same layout for 32-bit and 64-bit tasks,
and SNDRV_TIMER_IOCTL_TRIGGER takes no argument, so both commands can
be passed through unchanged.

The utimer selftest doesn't catch this when built with -m32: it takes
-ENOTTY from SNDRV_TIMER_IOCTL_CREATE to mean CONFIG_SND_UTIMER=n and
skips.

Fixes: 37745918e0 ("ALSA: timer: Introduce virtual userspace-driven timers")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Danish Khateeb <danishkhateeb03@gmail.com>
Link: https://patch.msgid.link/20260928182352.309457-1-danishkhateeb03@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Danish Khateeb 2026-09-28 13:23:52 -05:00 committed by Takashi Iwai
parent d243bb01c8
commit 1bbc033983
2 changed files with 2 additions and 0 deletions
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1
sound/core/timer.c
View File

@ -2176,6 +2176,7 @@ static const struct file_operations snd_utimer_fops = {
.llseek = noop_llseek,
.release = snd_utimer_release,
.unlocked_ioctl = snd_utimer_ioctl,
.compat_ioctl = snd_utimer_ioctl,
};
static int snd_utimer_start(struct snd_timer *t)

1
sound/core/timer_compat.c
View File

@ -99,6 +99,7 @@ static long __snd_timer_user_ioctl_compat(struct file *file, unsigned int cmd,
case SNDRV_TIMER_IOCTL_PAUSE:
case SNDRV_TIMER_IOCTL_PAUSE_OLD:
case SNDRV_TIMER_IOCTL_NEXT_DEVICE:
case SNDRV_TIMER_IOCTL_CREATE:
return __snd_timer_user_ioctl(file, cmd, (unsigned long)argp, true);
case SNDRV_TIMER_IOCTL_GPARAMS32:
return snd_timer_user_gparams_compat(file, argp);