Patch "ALSA: rawmidi: Drop register_mutex in snd_rawmidi_free()" has been added to the 6.0-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

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

    ALSA: rawmidi: Drop register_mutex in snd_rawmidi_free()

to the 6.0-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-rawmidi-drop-register_mutex-in-snd_rawmidi_free.patch
and it can be found in the queue-6.0 subdirectory.

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


>From a70aef7982b012e86dfd39fbb235e76a21ae778a Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@xxxxxxx>
Date: Tue, 11 Oct 2022 09:01:46 +0200
Subject: ALSA: rawmidi: Drop register_mutex in snd_rawmidi_free()

From: Takashi Iwai <tiwai@xxxxxxx>

commit a70aef7982b012e86dfd39fbb235e76a21ae778a upstream.

The register_mutex taken around the dev_unregister callback call in
snd_rawmidi_free() may potentially lead to a mutex deadlock, when OSS
emulation and a hot unplug are involved.

Since the mutex doesn't protect the actual race (as the registration
itself is already protected by another means), let's drop it.

Link: https://lore.kernel.org/r/CAB7eexJP7w1B0mVgDF0dQ+gWor7UdkiwPczmL7pn91xx8xpzOA@xxxxxxxxxxxxxx
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20221011070147.7611-1-tiwai@xxxxxxx
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 sound/core/rawmidi.c |    2 --
 1 file changed, 2 deletions(-)

--- a/sound/core/rawmidi.c
+++ b/sound/core/rawmidi.c
@@ -1899,10 +1899,8 @@ static int snd_rawmidi_free(struct snd_r
 
 	snd_info_free_entry(rmidi->proc_entry);
 	rmidi->proc_entry = NULL;
-	mutex_lock(&register_mutex);
 	if (rmidi->ops && rmidi->ops->dev_unregister)
 		rmidi->ops->dev_unregister(rmidi);
-	mutex_unlock(&register_mutex);
 
 	snd_rawmidi_free_substreams(&rmidi->streams[SNDRV_RAWMIDI_STREAM_INPUT]);
 	snd_rawmidi_free_substreams(&rmidi->streams[SNDRV_RAWMIDI_STREAM_OUTPUT]);


Patches currently in stable-queue which might be from tiwai@xxxxxxx are

queue-6.0/alsa-rawmidi-drop-register_mutex-in-snd_rawmidi_free.patch
queue-6.0/alsa-oss-fix-potential-deadlock-at-unregistration.patch
queue-6.0/alsa-usb-audio-fix-potential-memory-leaks.patch
queue-6.0/alsa-hda-realtek-add-quirk-for-asus-gv601r-laptop.patch
queue-6.0/alsa-hda-realtek-correct-pin-configs-for-asus-g533z.patch
queue-6.0/alsa-hda-realtek-remove-alc289_fixup_dual_spk-for-dell-5530.patch
queue-6.0/alsa-hda-realtek-add-intel-reference-ssid-to-support-headset-keys.patch
queue-6.0/alsa-usb-audio-fix-null-dererence-at-error-path.patch