FAILED: patch "[PATCH] ALSA: timer: Handle userspace-driven timer ioctls from 32-bit tasks" failed to apply to 6.12-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 1bbc033983b76f41d51d4a48838bf94c5e6b6f50
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107051806-failed-6.12-1bbc033983b7@kernel.org' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From 1bbc033983b76f41d51d4a48838bf94c5e6b6f50 Mon Sep 17 00:00:00 2001
From: Danish Khateeb <danishkhateeb03@gmail.com>
Date: Mon, 28 Sep 2026 13:23:52 -0500
Subject: [PATCH] ALSA: timer: Handle userspace-driven timer ioctls from 32-bit
 tasks

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: 37745918e0e7 ("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>
---
 sound/core/timer.c        | 1 +
 sound/core/timer_compat.c | 1 +
 2 files changed, 2 insertions(+)

diff --git a/sound/core/timer.c b/sound/core/timer.c
index 679b264356709..69a59b25fe0a8 100644
--- a/sound/core/timer.c
+++ b/sound/core/timer.c
@@ -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)
diff --git a/sound/core/timer_compat.c b/sound/core/timer_compat.c
index 25ee81c1668b7..5bab00466de7f 100644
--- a/sound/core/timer_compat.c
+++ b/sound/core/timer_compat.c
@@ -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);
-- 
2.53.0