[PATCH 5.16 011/126] ALSA: hda: Fix UAF of leds class devs at unbinding

Greg Kroah-Hartman
2022-02-07T11:58:56Z

From: Takashi Iwai <tiwai@suse.de>

commit 549f8ffc7b2f7561bea7f90930b6c5104318e87b upstream.

The LED class devices that are created by HD-audio codec drivers are
registered via devm_led_classdev_register() and associated with the
HD-audio codec device. Unfortunately, it turned out that the devres
release doesn't work for this case; namely, since the codec resource
release happens before the devm call chain, it triggers a NULL
dereference or a UAF for a stale set_brightness_delay callback.

For fixing the bug, this patch changes the LED class device register
and unregister in a manual manner without devres, keeping the
instances in hda_gen_spec.

Reported-by: Alexander Sergeyev <sergeev917@gmail.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20220111195229.a77wrpjclqwrx4bx@localhost.localdomain
Link: https://lore.kernel.org/r/20220126145011.16728-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
sound/pci/hda/hda_generic.c | 17 +++++++++++++++--
sound/pci/hda/hda_generic.h | 3 +++
2 files changed, 18 insertions(+), 2 deletions(-)

--- a/sound/pci/hda/hda_generic.c
+++ b/sound/pci/hda/hda_generic.c
@@ -91,6 +91,12 @@ static void snd_hda_gen_spec_free(struct
free_kctls(spec);
snd_array_free(&spec->paths);
snd_array_free(&spec->loopback_list);
+#ifdef CONFIG_SND_HDA_GENERIC_LEDS
+ if (spec->led_cdevs[LED_AUDIO_MUTE])
+ led_classdev_unregister(spec->led_cdevs[LED_AUDIO_MUTE]);
+ if (spec->led_cdevs[LED_AUDIO_MICMUTE])
+ led_classdev_unregister(spec->led_cdevs[LED_AUDIO_MICMUTE]);
+#endif
}

/*
@@ -3922,7 +3928,10 @@ static int create_mute_led_cdev(struct h
enum led_brightness),
bool micmute)
{
+ struct hda_gen_spec *spec = codec->spec;
struct led_classdev *cdev;
+ int idx = micmute ? LED_AUDIO_MICMUTE : LED_AUDIO_MUTE;
+ int err;

cdev = devm_kzalloc(&codec->core.dev, sizeof(*cdev), GFP_KERNEL);
if (!cdev)
@@ -3932,10 +3941,14 @@ static int create_mute_led_cdev(struct h
cdev->max_brightness = 1;
cdev->default_trigger = micmute ? "audio-micmute" : "audio-mute";
cdev->brightness_set_blocking = callback;
- cdev->brightness = ledtrig_audio_get(micmute ? LED_AUDIO_MICMUTE : LED_AUDIO_MUTE);
+ cdev->brightness = ledtrig_audio_get(idx);
cdev->flags = LED_CORE_SUSPENDRESUME;

- return devm_led_classdev_register(&codec->core.dev, cdev);
+ err = led_classdev_register(&codec->core.dev, cdev);
+ if (err < 0)
+ return err;
+ spec->led_cdevs[idx] = cdev;
+ return 0;
}

/**
--- a/sound/pci/hda/hda_generic.h
+++ b/sound/pci/hda/hda_generic.h
@@ -294,6 +294,9 @@ struct hda_gen_spec {
struct hda_jack_callback *cb);
void (*mic_autoswitch_hook)(struct hda_codec *codec,
struct hda_jack_callback *cb);
+
+ /* leds */
+ struct led_classdev *led_cdevs[NUM_AUDIO_LEDS];
};

/* values for add_stereo_mix_input flag */