@@ -162,7 +162,6 @@ int snd_unregister_oss_device(int type, struct snd_card *card, int dev)
mutex_unlock(&sound_oss_mutex);
return -ENOENT;
}
- unregister_sound_special(minor);
switch (SNDRV_MINOR_OSS_DEVICE(minor)) {
case SNDRV_MINOR_OSS_PCM:
track2 = SNDRV_MINOR_OSS(cidx, SNDRV_MINOR_OSS_AUDIO);
@@ -174,12 +173,18 @@ int snd_unregister_oss_device(int type, struct snd_card *card, int dev)
track2 = SNDRV_MINOR_OSS(cidx, SNDRV_MINOR_OSS_DMMIDI1);
break;
}
- if (track2 >= 0) {
- unregister_sound_special(track2);
+ if (track2 >= 0)
snd_oss_minors[track2] = NULL;
- }
snd_oss_minors[minor] = NULL;
mutex_unlock(&sound_oss_mutex);
+
+ /* call unregister_sound_special() outside sound_oss_mutex;
+ * otherwise may deadlock, as it can trigger the release of a card
+ */
+ unregister_sound_special(minor);
+ if (track2 >= 0)
+ unregister_sound_special(track2);
+
kfree(mptr);
return 0;
}
We took sound_oss_mutex around the calls of unregister_sound_special() at unregistering OSS devices. This may, however, lead to a deadlock, because we manage the card release via the card's device object, and the release may happen at unregister_sound_special() call -- which will take sound_oss_mutex again in turn. Although the deadlock might be fixed by relaxing the rawmidi mutex in the previous commit, it's safer to move unregister_sound_special() calls themselves out of the sound_oss_mutex, too. The call is race-safe as the function has a spinlock protection by itself. Link: https://lore.kernel.org/r/CAB7eexJP7w1B0mVgDF0dQ+gWor7UdkiwPczmL7pn91xx8xpzOA@mail.gmail.com Cc: <stable@vger.kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de> --- sound/core/sound_oss.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-)