Patch "ALSA: jack: Fix mutex call in snd_jack_report()" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    ALSA: jack: Fix mutex call in snd_jack_report()

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     alsa-jack-fix-mutex-call-in-snd_jack_report.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 42ada51b21a1d74cab694d8963a0185bcb2956e9
Author: Takashi Iwai <tiwai@xxxxxxx>
Date:   Thu Jul 6 17:53:57 2023 +0200

    ALSA: jack: Fix mutex call in snd_jack_report()
    
    [ Upstream commit 89dbb335cb6a627a4067bc42caa09c8bc3326d40 ]
    
    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@xxxxxxxxxx>
    Closes: https://lore.kernel.org/r/cf95f7fe-a748-4990-8378-000491b40329@moroto.mountain
    Tested-by: Amadeusz Sławiński <amadeuszx.slawinski@xxxxxxxxxxxxxxx>
    Cc: <stable@xxxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230706155357.3470-1-tiwai@xxxxxxx
    Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/sound/core/jack.c b/sound/core/jack.c
index 45e28db6ea38d..8a9baa084191f 100644
--- a/sound/core/jack.c
+++ b/sound/core/jack.c
@@ -364,6 +364,7 @@ void snd_jack_report(struct snd_jack *jack, int status)
 {
 	struct snd_jack_kctl *jack_kctl;
 #ifdef CONFIG_SND_JACK_INPUT_DEV
+	struct input_dev *idev;
 	int i;
 #endif
 
@@ -375,30 +376,28 @@ 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;
 
 		if (jack->type & testbit)
-			input_report_key(jack->input_dev, jack->key[i],
+			input_report_key(idev, jack->key[i],
 					 status & testbit);
 	}
 
 	for (i = 0; i < ARRAY_SIZE(jack_switch_types); i++) {
 		int testbit = 1 << i;
 		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);