diff options
| author | Takashi Iwai <tiwai@suse.de> | 2022-10-11 09:01:47 +0200 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2022-10-11 09:02:43 +0200 |
| commit | 97d917879d7f92df09c3f21fd54609a8bcd654b2 (patch) | |
| tree | 99dd7e3590f0520dfb1aae4fa3d5ad05cb17c587 /sound | |
| parent | a70aef7982b012e86dfd39fbb235e76a21ae778a (diff) | |
| download | lwn-97d917879d7f92df09c3f21fd54609a8bcd654b2.tar.gz lwn-97d917879d7f92df09c3f21fd54609a8bcd654b2.zip | |
ALSA: oss: Fix potential deadlock at unregistration
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>
Link: https://lore.kernel.org/r/20221011070147.7611-2-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound')
| -rw-r--r-- | sound/core/sound_oss.c | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/sound/core/sound_oss.c b/sound/core/sound_oss.c index 7ed0a2a91035..2751bf2ff61b 100644 --- a/sound/core/sound_oss.c +++ b/sound/core/sound_oss.c @@ -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; } |