* [RFC PATCH] sound: line6: Fix race condition in line6_probe
@ 2021-05-17 13:27 Hyeonggon Yoo
2021-05-17 13:43 ` Takashi Iwai
0 siblings, 1 reply; 6+ messages in thread
From: Hyeonggon Yoo @ 2021-05-17 13:27 UTC (permalink / raw)
To: Jaroslav Kysela, Takashi Iwai, Greg Kroah-Hartman, Oliver Neukum,
Hyeonggon Yoo, Vasily Khoruzhick
Cc: alsa-devel, linux-kernel
syzbot reported general protection fault in midibuf_is_full.
the cause is linemidi pointer in struct usb_line6 isn't properly
initialized.
the pointer isn't initialized because there is race condition
in line6_probe. it calls line6_init_cap_control first, which submits urb.
and then it initializes it's data using private_init function.
so it's possible line6_data_received is called before it's
data isn't initialized.
Link: https://lkml.org/lkml/2021/5/17/543
Reported-by: syzbot+0d2b3feb0a2887862e06@syzkallerlkml..appspotmail.com
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
---
sound/usb/line6/driver.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
index a030dd65eb28..2c183a2a30f0 100644
--- a/sound/usb/line6/driver.c
+++ b/sound/usb/line6/driver.c
@@ -788,17 +788,17 @@ int line6_probe(struct usb_interface *interface,
line6_get_usb_properties(line6);
+ /* initialize device data based on device: */
+ ret = private_init(line6, id);
+ if (ret < 0)
+ goto error;
+
if (properties->capabilities & LINE6_CAP_CONTROL) {
ret = line6_init_cap_control(line6);
if (ret < 0)
goto error;
}
- /* initialize device data based on device: */
- ret = private_init(line6, id);
- if (ret < 0)
- goto error;
-
/* creation of additional special files should go here */
dev_info(&interface->dev, "Line 6 %s now attached\n",
--
2.25.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [RFC PATCH] sound: line6: Fix race condition in line6_probe
2021-05-17 13:27 [RFC PATCH] sound: line6: Fix race condition in line6_probe Hyeonggon Yoo
@ 2021-05-17 13:43 ` Takashi Iwai
2021-05-17 14:48 ` Hyeonggon Yoo
2021-05-17 14:56 ` Hyeonggon Yoo
0 siblings, 2 replies; 6+ messages in thread
From: Takashi Iwai @ 2021-05-17 13:43 UTC (permalink / raw)
To: Hyeonggon Yoo
Cc: Jaroslav Kysela, Takashi Iwai, Greg Kroah-Hartman, Oliver Neukum,
Vasily Khoruzhick, alsa-devel, linux-kernel
On Mon, 17 May 2021 15:27:25 +0200,
Hyeonggon Yoo wrote:
>
> syzbot reported general protection fault in midibuf_is_full.
> the cause is linemidi pointer in struct usb_line6 isn't properly
> initialized.
>
> the pointer isn't initialized because there is race condition
> in line6_probe. it calls line6_init_cap_control first, which submits urb.
> and then it initializes it's data using private_init function.
>
> so it's possible line6_data_received is called before it's
> data isn't initialized.
>
> Link: https://lkml.org/lkml/2021/5/17/543
> Reported-by: syzbot+0d2b3feb0a2887862e06@syzkallerlkml..appspotmail.com
> Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Thanks for the patch! It's an issue I'm tracking now, too, and you
submitted quicker. But, unfortunately, this swap does seem yet
another potential race between the private_init call and
line6_init_cap_control(). The actually needed initialization is
line6_init_mid() call, and this can be fixed by moving to the
appropriate place instead of inside each private_init callback.
So my current fix is like below.
thanks,
Takashi
---
diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
index a030dd65eb28..9602929b7de9 100644
--- a/sound/usb/line6/driver.c
+++ b/sound/usb/line6/driver.c
@@ -699,6 +699,10 @@ static int line6_init_cap_control(struct usb_line6 *line6)
line6->buffer_message = kmalloc(LINE6_MIDI_MESSAGE_MAXLEN, GFP_KERNEL);
if (!line6->buffer_message)
return -ENOMEM;
+
+ ret = line6_init_midi(line6);
+ if (ret < 0)
+ return ret;
} else {
ret = line6_hwdep_init(line6);
if (ret < 0)
diff --git a/sound/usb/line6/pod.c b/sound/usb/line6/pod.c
index cd44cb5f1310..16e644330c4d 100644
--- a/sound/usb/line6/pod.c
+++ b/sound/usb/line6/pod.c
@@ -376,11 +376,6 @@ static int pod_init(struct usb_line6 *line6,
if (err < 0)
return err;
- /* initialize MIDI subsystem: */
- err = line6_init_midi(line6);
- if (err < 0)
- return err;
-
/* initialize PCM subsystem: */
err = line6_init_pcm(line6, &pod_pcm_properties);
if (err < 0)
diff --git a/sound/usb/line6/variax.c b/sound/usb/line6/variax.c
index ed158f04de80..1376fc405c7f 100644
--- a/sound/usb/line6/variax.c
+++ b/sound/usb/line6/variax.c
@@ -172,11 +172,6 @@ static int variax_init(struct usb_line6 *line6,
if (variax->buffer_activate == NULL)
return -ENOMEM;
- /* initialize MIDI subsystem: */
- err = line6_init_midi(&variax->line6);
- if (err < 0)
- return err;
-
/* initiate startup procedure: */
schedule_delayed_work(&line6->startup_work,
msecs_to_jiffies(VARIAX_STARTUP_DELAY1));
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [RFC PATCH] sound: line6: Fix race condition in line6_probe
2021-05-17 13:43 ` Takashi Iwai
@ 2021-05-17 14:48 ` Hyeonggon Yoo
2021-05-17 14:57 ` Takashi Iwai
2021-05-17 14:56 ` Hyeonggon Yoo
1 sibling, 1 reply; 6+ messages in thread
From: Hyeonggon Yoo @ 2021-05-17 14:48 UTC (permalink / raw)
To: Takashi Iwai
Cc: Jaroslav Kysela, Takashi Iwai, Greg Kroah-Hartman, Oliver Neukum,
Vasily Khoruzhick, alsa-devel, linux-kernel
On Mon, May 17, 2021 at 03:43:24PM +0200, Takashi Iwai wrote:
> The actually needed initialization is
> line6_init_mid() call, and this can be fixed by moving to the
> appropriate place instead of inside each private_init callback.
Oh, I missed it! there was another caller of line6_init_midi.
your fix seems promising to me. it's putting line6_init_midi
to the right place.
by the way looking at code, I think this driver needs some
refactoring... it doesn't handle exceptions well.
Thanks,
Hyeonggon
> ---
> diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
> index a030dd65eb28..9602929b7de9 100644
> --- a/sound/usb/line6/driver.c
> +++ b/sound/usb/line6/driver.c
> @@ -699,6 +699,10 @@ static int line6_init_cap_control(struct usb_line6 *line6)
> line6->buffer_message = kmalloc(LINE6_MIDI_MESSAGE_MAXLEN, GFP_KERNEL);
> if (!line6->buffer_message)
> return -ENOMEM;
> +
> + ret = line6_init_midi(line6);
> + if (ret < 0)
> + return ret;
> } else {
> ret = line6_hwdep_init(line6);
> if (ret < 0)
> diff --git a/sound/usb/line6/pod.c b/sound/usb/line6/pod.c
> index cd44cb5f1310..16e644330c4d 100644
> --- a/sound/usb/line6/pod.c
> +++ b/sound/usb/line6/pod.c
> @@ -376,11 +376,6 @@ static int pod_init(struct usb_line6 *line6,
> if (err < 0)
> return err;
>
> - /* initialize MIDI subsystem: */
> - err = line6_init_midi(line6);
> - if (err < 0)
> - return err;
> -
> /* initialize PCM subsystem: */
> err = line6_init_pcm(line6, &pod_pcm_properties);
> if (err < 0)
> diff --git a/sound/usb/line6/variax.c b/sound/usb/line6/variax.c
> index ed158f04de80..1376fc405c7f 100644
> --- a/sound/usb/line6/variax.c
> +++ b/sound/usb/line6/variax.c
> @@ -172,11 +172,6 @@ static int variax_init(struct usb_line6 *line6,
> if (variax->buffer_activate == NULL)
> return -ENOMEM;
>
> - /* initialize MIDI subsystem: */
> - err = line6_init_midi(&variax->line6);
> - if (err < 0)
> - return err;
> -
> /* initiate startup procedure: */
> schedule_delayed_work(&line6->startup_work,
> msecs_to_jiffies(VARIAX_STARTUP_DELAY1));
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC PATCH] sound: line6: Fix race condition in line6_probe
2021-05-17 13:43 ` Takashi Iwai
2021-05-17 14:48 ` Hyeonggon Yoo
@ 2021-05-17 14:56 ` Hyeonggon Yoo
1 sibling, 0 replies; 6+ messages in thread
From: Hyeonggon Yoo @ 2021-05-17 14:56 UTC (permalink / raw)
To: Takashi Iwai
Cc: Jaroslav Kysela, Takashi Iwai, Greg Kroah-Hartman, Oliver Neukum,
Vasily Khoruzhick, alsa-devel, linux-kernel, 42.hyeyoo
I'm kinda new to linux,
but tell me any time if there's something I can help!
thanks,
Hyeonggon
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC PATCH] sound: line6: Fix race condition in line6_probe
2021-05-17 14:48 ` Hyeonggon Yoo
@ 2021-05-17 14:57 ` Takashi Iwai
2021-05-17 15:03 ` Hyeonggon Yoo
0 siblings, 1 reply; 6+ messages in thread
From: Takashi Iwai @ 2021-05-17 14:57 UTC (permalink / raw)
To: Hyeonggon Yoo
Cc: Jaroslav Kysela, Takashi Iwai, Greg Kroah-Hartman, Oliver Neukum,
Vasily Khoruzhick, alsa-devel, linux-kernel
On Mon, 17 May 2021 16:48:11 +0200,
Hyeonggon Yoo wrote:
>
> On Mon, May 17, 2021 at 03:43:24PM +0200, Takashi Iwai wrote:
> > The actually needed initialization is
> > line6_init_mid() call, and this can be fixed by moving to the
> > appropriate place instead of inside each private_init callback.
>
> Oh, I missed it! there was another caller of line6_init_midi.
> your fix seems promising to me. it's putting line6_init_midi
> to the right place.
>
> by the way looking at code, I think this driver needs some
> refactoring... it doesn't handle exceptions well.
Yes, there can be likely a few other holes in this driver, but for
fixing them, we'd need an actual test device. The initialization
procedure of this device seems complex (multi-staged) and very
sensitive.
Takashi
>
> Thanks,
>
> Hyeonggon
> > ---
> > diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
> > index a030dd65eb28..9602929b7de9 100644
> > --- a/sound/usb/line6/driver.c
> > +++ b/sound/usb/line6/driver.c
> > @@ -699,6 +699,10 @@ static int line6_init_cap_control(struct usb_line6 *line6)
> > line6->buffer_message = kmalloc(LINE6_MIDI_MESSAGE_MAXLEN, GFP_KERNEL);
> > if (!line6->buffer_message)
> > return -ENOMEM;
> > +
> > + ret = line6_init_midi(line6);
> > + if (ret < 0)
> > + return ret;
> > } else {
> > ret = line6_hwdep_init(line6);
> > if (ret < 0)
> > diff --git a/sound/usb/line6/pod.c b/sound/usb/line6/pod.c
> > index cd44cb5f1310..16e644330c4d 100644
> > --- a/sound/usb/line6/pod.c
> > +++ b/sound/usb/line6/pod.c
> > @@ -376,11 +376,6 @@ static int pod_init(struct usb_line6 *line6,
> > if (err < 0)
> > return err;
> >
> > - /* initialize MIDI subsystem: */
> > - err = line6_init_midi(line6);
> > - if (err < 0)
> > - return err;
> > -
> > /* initialize PCM subsystem: */
> > err = line6_init_pcm(line6, &pod_pcm_properties);
> > if (err < 0)
> > diff --git a/sound/usb/line6/variax.c b/sound/usb/line6/variax.c
> > index ed158f04de80..1376fc405c7f 100644
> > --- a/sound/usb/line6/variax.c
> > +++ b/sound/usb/line6/variax.c
> > @@ -172,11 +172,6 @@ static int variax_init(struct usb_line6 *line6,
> > if (variax->buffer_activate == NULL)
> > return -ENOMEM;
> >
> > - /* initialize MIDI subsystem: */
> > - err = line6_init_midi(&variax->line6);
> > - if (err < 0)
> > - return err;
> > -
> > /* initiate startup procedure: */
> > schedule_delayed_work(&line6->startup_work,
> > msecs_to_jiffies(VARIAX_STARTUP_DELAY1));
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC PATCH] sound: line6: Fix race condition in line6_probe
2021-05-17 14:57 ` Takashi Iwai
@ 2021-05-17 15:03 ` Hyeonggon Yoo
0 siblings, 0 replies; 6+ messages in thread
From: Hyeonggon Yoo @ 2021-05-17 15:03 UTC (permalink / raw)
To: Takashi Iwai
Cc: Jaroslav Kysela, Takashi Iwai, Greg Kroah-Hartman, Oliver Neukum,
Vasily Khoruzhick, alsa-devel, linux-kernel
On Mon, May 17, 2021 at 04:57:28PM +0200, Takashi Iwai wrote:
> Yes, there can be likely a few other holes in this driver, but for
> fixing them, we'd need an actual test device. The initialization
> procedure of this device seems complex (multi-staged) and very
> sensitive.
> Takashi
Yeap, this driver is so complex,
and I agree that we need actual device to test
if we do that big scale of refactoring.
Sadly I don't have one :(
Thanks,
Hyeonggon
^ permalink raw reply [flat|nested] 6+ messages in thread
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2021-05-17 13:27 [RFC PATCH] sound: line6: Fix race condition in line6_probe Hyeonggon Yoo
2021-05-17 13:43 ` Takashi Iwai
2021-05-17 14:48 ` Hyeonggon Yoo
2021-05-17 14:57 ` Takashi Iwai
2021-05-17 15:03 ` Hyeonggon Yoo
2021-05-17 14:56 ` Hyeonggon Yoo
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