[PATCH 6.4 521/800] ALSA: jack: Fix mutex call in snd_jack_report()

Greg Kroah-Hartman
2023-07-16T20:17:18Z

From: Takashi Iwai <tiwai@suse.de>

commit 89dbb335cb6a627a4067bc42caa09c8bc3326d40 upstream.

snd_jack_report() is supposed to be callable from an IRQ context, too,
and it's indeed used in that way from virtsnd driver. The fix for
input_dev race in commit 1b6a6fc5280e ("ALSA: jack: Access input_dev
under mutex"), however, introduced a mutex lock in snd_jack_report(),
and this resulted in a potential sleep-in-atomic.

For addressing that problem, this patch changes the relevant code to
use the object get/put and removes the mutex usage. That is,
snd_jack_report(), it takes input_get_device() and leaves with
input_put_device() for assuring the input_dev being assigned.

Although the whole mutex could be reduced, we keep it because it can
be still a protection for potential races between creation and
deletion.

Fixes: 1b6a6fc5280e ("ALSA: jack: Access input_dev under mutex")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/cf95f7fe-a748-4990-8378-000491b40329@moroto.mountain
Tested-by: Amadeusz Sławiński <amadeuszx.slawinski@linux.intel.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20230706155357.3470-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
sound/core/jack.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)

--- a/sound/core/jack.c
+++ b/sound/core/jack.c
@@ -654,6 +654,7 @@ void snd_jack_report(struct snd_jack *ja
struct snd_jack_kctl *jack_kctl;
unsigned int mask_bits = 0;
#ifdef CONFIG_SND_JACK_INPUT_DEV
+ struct input_dev *idev;
int i;
#endif

@@ -670,17 +671,15 @@ void snd_jack_report(struct snd_jack *ja
status & jack_kctl->mask_bits);

#ifdef CONFIG_SND_JACK_INPUT_DEV
- mutex_lock(&jack->input_dev_lock);
- if (!jack->input_dev) {
- mutex_unlock(&jack->input_dev_lock);
+ idev = input_get_device(jack->input_dev);
+ if (!idev)
return;
- }

for (i = 0; i < ARRAY_SIZE(jack->key); i++) {
int testbit = ((SND_JACK_BTN_0 >> i) & ~mask_bits);

if (jack->type & testbit)
- input_report_key(jack->input_dev, jack->key[i],
+ input_report_key(idev, jack->key[i],
status & testbit);
}

@@ -688,13 +687,13 @@ void snd_jack_report(struct snd_jack *ja
int testbit = ((1 << i) & ~mask_bits);

if (jack->type & testbit)
- input_report_switch(jack->input_dev,
+ input_report_switch(idev,
jack_switch_types[i],
status & testbit);
}

- input_sync(jack->input_dev);
- mutex_unlock(&jack->input_dev_lock);
+ input_sync(idev);
+ input_put_device(idev);
#endif /* CONFIG_SND_JACK_INPUT_DEV */
}
EXPORT_SYMBOL(snd_jack_report);