ALSA: jack: Fix mutex call in snd_jack_report()

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>

diff --git a/sound/core/jack.c b/sound/core/jack.c
index 88493cc31914b7c842cea3b01e81f95a006cd1ed..03d155ed362b47c41ec453db99646aaecdfd38f0 100644 (file)
--- a/sound/core/jack.c
+++ b/sound/core/jack.c
@@ -654,6 +654,7 @@ void snd_jack_report(struct snd_jack *jack, int status)
        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 *jack, int status)
                                             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 *jack, int status)
                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);