[alsa-devel] [PATCH] ALSA: usb-audio: Fix memory leak in __snd_usbmidi_create

[alsa-devel] [PATCH] ALSA: usb-audio: Fix memory leak in __snd_usbmidi_create

[Navid Emamdoost]

In the implementation of __snd_usbmidi_create() there is a memory leak
caused by incorrect goto destination. Go to free_midi if
snd_usbmidi_create_endpoints_midiman() or snd_usbmidi_create_endpoints()
fail.

Fixes: 731209cc0417 ("ALSA: usb-midi: Use common error handling code in __snd_usbmidi_create()")
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
---
 sound/usb/midi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/usb/midi.c b/sound/usb/midi.c
index b737f0ec77d0..22db37fbfbbd 100644
--- a/sound/usb/midi.c
+++ b/sound/usb/midi.c
@@ -2476,7 +2476,7 @@ int __snd_usbmidi_create(struct snd_card *card,
 	else
 		err = snd_usbmidi_create_endpoints(umidi, endpoints);
 	if (err < 0)
-		goto exit;
+		goto free_midi;
 
 	usb_autopm_get_interface_no_resume(umidi->iface);
 
-- 
2.17.1

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Re: [alsa-devel] [PATCH] ALSA: usb-audio: Fix memory leak in __snd_usbmidi_create

[Takashi Iwai]

On Sun, 27 Oct 2019 23:10:06 +0100,
Navid Emamdoost wrote:
> 
> In the implementation of __snd_usbmidi_create() there is a memory leak
> caused by incorrect goto destination. Go to free_midi if
> snd_usbmidi_create_endpoints_midiman() or snd_usbmidi_create_endpoints()
> fail.

No, this will lead to double-free.  After registering the rawmidi
interface at snd_usbmidi_create_rawmidi(), the common destructor will
be called via rawmidi private_free callback, and this will release the
all resources already.


thanks,

Takashi

> 
> Fixes: 731209cc0417 ("ALSA: usb-midi: Use common error handling code in __snd_usbmidi_create()")
> Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
> ---
>  sound/usb/midi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sound/usb/midi.c b/sound/usb/midi.c
> index b737f0ec77d0..22db37fbfbbd 100644
> --- a/sound/usb/midi.c
> +++ b/sound/usb/midi.c
> @@ -2476,7 +2476,7 @@ int __snd_usbmidi_create(struct snd_card *card,
>  	else
>  		err = snd_usbmidi_create_endpoints(umidi, endpoints);
>  	if (err < 0)
> -		goto exit;
> +		goto free_midi;
>  
>  	usb_autopm_get_interface_no_resume(umidi->iface);
>  
> -- 
> 2.17.1
> 
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Re: [alsa-devel] [PATCH] ALSA: usb-audio: Fix memory leak in __snd_usbmidi_create

[Navid Emamdoost]

Thanks for the explanation,

On Mon, Oct 28, 2019 at 1:27 AM Takashi Iwai <tiwai@suse.de> wrote:
>
> On Sun, 27 Oct 2019 23:10:06 +0100,
> Navid Emamdoost wrote:
> >
> > In the implementation of __snd_usbmidi_create() there is a memory leak
> > caused by incorrect goto destination. Go to free_midi if
> > snd_usbmidi_create_endpoints_midiman() or snd_usbmidi_create_endpoints()
> > fail.
>
> No, this will lead to double-free.  After registering the rawmidi
> interface at snd_usbmidi_create_rawmidi(), the common destructor will
> be called via rawmidi private_free callback, and this will release the
> all resources already.
Now I can see how rawmidi private_free is set up to release the
resources, but what concerns me is that at the moment of endpoint/port
creation umidi is not yet added to the midi_list.
In other words, what I see is that we still have just one local
pointer to umidi if any of snd_usbmidi_create_endpoint* fail.
Am I missing something?


>
>
> thanks,
>
> Takashi
>
> >
> > Fixes: 731209cc0417 ("ALSA: usb-midi: Use common error handling code in __snd_usbmidi_create()")
> > Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
> > ---
> >  sound/usb/midi.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/sound/usb/midi.c b/sound/usb/midi.c
> > index b737f0ec77d0..22db37fbfbbd 100644
> > --- a/sound/usb/midi.c
> > +++ b/sound/usb/midi.c
> > @@ -2476,7 +2476,7 @@ int __snd_usbmidi_create(struct snd_card *card,
> >       else
> >               err = snd_usbmidi_create_endpoints(umidi, endpoints);
> >       if (err < 0)
> > -             goto exit;
> > +             goto free_midi;
> >
> >       usb_autopm_get_interface_no_resume(umidi->iface);
> >
> > --
> > 2.17.1
> >



-- 
Navid.
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Re: [alsa-devel] [PATCH] ALSA: usb-audio: Fix memory leak in __snd_usbmidi_create

[Takashi Iwai]

On Mon, 28 Oct 2019 17:25:41 +0100,
Navid Emamdoost wrote:
> 
> Thanks for the explanation,
> 
> On Mon, Oct 28, 2019 at 1:27 AM Takashi Iwai <tiwai@suse.de> wrote:
> >
> > On Sun, 27 Oct 2019 23:10:06 +0100,
> > Navid Emamdoost wrote:
> > >
> > > In the implementation of __snd_usbmidi_create() there is a memory leak
> > > caused by incorrect goto destination. Go to free_midi if
> > > snd_usbmidi_create_endpoints_midiman() or snd_usbmidi_create_endpoints()
> > > fail.
> >
> > No, this will lead to double-free.  After registering the rawmidi
> > interface at snd_usbmidi_create_rawmidi(), the common destructor will
> > be called via rawmidi private_free callback, and this will release the
> > all resources already.
> Now I can see how rawmidi private_free is set up to release the
> resources, but what concerns me is that at the moment of endpoint/port
> creation umidi is not yet added to the midi_list.
> In other words, what I see is that we still have just one local
> pointer to umidi if any of snd_usbmidi_create_endpoint* fail.
> Am I missing something?

The rawmidi object that is created via snd_rawmidi_new() is managed
via snd_device list, and it's traversed at snd_card_disconnect() and
snd_card_free() calls.  It's something like devm-stuff (but
implemented in a different way).  The midi_list is an explicit list
for the USB MIDI driver, and it's an individual one from the device
list.


Takashi

> 
> 
> >
> >
> > thanks,
> >
> > Takashi
> >
> > >
> > > Fixes: 731209cc0417 ("ALSA: usb-midi: Use common error handling code in __snd_usbmidi_create()")
> > > Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
> > > ---
> > >  sound/usb/midi.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/sound/usb/midi.c b/sound/usb/midi.c
> > > index b737f0ec77d0..22db37fbfbbd 100644
> > > --- a/sound/usb/midi.c
> > > +++ b/sound/usb/midi.c
> > > @@ -2476,7 +2476,7 @@ int __snd_usbmidi_create(struct snd_card *card,
> > >       else
> > >               err = snd_usbmidi_create_endpoints(umidi, endpoints);
> > >       if (err < 0)
> > > -             goto exit;
> > > +             goto free_midi;
> > >
> > >       usb_autopm_get_interface_no_resume(umidi->iface);
> > >
> > > --
> > > 2.17.1
> > >
> 
> 
> 
> -- 
> Navid.
> 
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Re: [alsa-devel] [PATCH] ALSA: usb-audio: Fix memory leak in __snd_usbmidi_create

[Navid Emamdoost]

On Mon, Oct 28, 2019 at 11:38 AM Takashi Iwai <tiwai@suse.de> wrote:
>
> On Mon, 28 Oct 2019 17:25:41 +0100,
> Navid Emamdoost wrote:
> >
> > Thanks for the explanation,
> >
> > On Mon, Oct 28, 2019 at 1:27 AM Takashi Iwai <tiwai@suse.de> wrote:
> > >
> > > On Sun, 27 Oct 2019 23:10:06 +0100,
> > > Navid Emamdoost wrote:
> > > >
> > > > In the implementation of __snd_usbmidi_create() there is a memory leak
> > > > caused by incorrect goto destination. Go to free_midi if
> > > > snd_usbmidi_create_endpoints_midiman() or snd_usbmidi_create_endpoints()
> > > > fail.
> > >
> > > No, this will lead to double-free.  After registering the rawmidi
> > > interface at snd_usbmidi_create_rawmidi(), the common destructor will
> > > be called via rawmidi private_free callback, and this will release the
> > > all resources already.
> > Now I can see how rawmidi private_free is set up to release the
> > resources, but what concerns me is that at the moment of endpoint/port
> > creation umidi is not yet added to the midi_list.
> > In other words, what I see is that we still have just one local
> > pointer to umidi if any of snd_usbmidi_create_endpoint* fail.
> > Am I missing something?
>
> The rawmidi object that is created via snd_rawmidi_new() is managed
> via snd_device list, and it's traversed at snd_card_disconnect() and
> snd_card_free() calls.  It's something like devm-stuff (but
> implemented in a different way).  The midi_list is an explicit list
> for the USB MIDI driver, and it's an individual one from the device
> list.

Thanks for the clarification.

>
>
> Takashi
>
> >
> >
> > >
> > >
> > > thanks,
> > >
> > > Takashi
> > >
> > > >
> > > > Fixes: 731209cc0417 ("ALSA: usb-midi: Use common error handling code in __snd_usbmidi_create()")
> > > > Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
> > > > ---
> > > >  sound/usb/midi.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/sound/usb/midi.c b/sound/usb/midi.c
> > > > index b737f0ec77d0..22db37fbfbbd 100644
> > > > --- a/sound/usb/midi.c
> > > > +++ b/sound/usb/midi.c
> > > > @@ -2476,7 +2476,7 @@ int __snd_usbmidi_create(struct snd_card *card,
> > > >       else
> > > >               err = snd_usbmidi_create_endpoints(umidi, endpoints);
> > > >       if (err < 0)
> > > > -             goto exit;
> > > > +             goto free_midi;
> > > >
> > > >       usb_autopm_get_interface_no_resume(umidi->iface);
> > > >
> > > > --
> > > > 2.17.1
> > > >
> >
> >
> >
> > --
> > Navid.
> >



-- 
Navid.
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Re: [alsa-devel] [PATCH] ALSA: usb-audio: Fix memory leak in __snd_usbmidi_create

[Clemens Ladisch]

Navid Emamdoost wrote:
> On Mon, Oct 28, 2019 at 1:27 AM Takashi Iwai <tiwai@suse.de> wrote:
>> On Sun, 27 Oct 2019 23:10:06 +0100,
>> Navid Emamdoost wrote:
>>> In the implementation of __snd_usbmidi_create() there is a memory leak
>>> caused by incorrect goto destination. Go to free_midi if
>>> snd_usbmidi_create_endpoints_midiman() or snd_usbmidi_create_endpoints()
>>> fail.
>>
>> No, this will lead to double-free.  After registering the rawmidi
>> interface at snd_usbmidi_create_rawmidi(), the common destructor will
>> be called via rawmidi private_free callback, and this will release the
>> all resources already.
>
> Now I can see how rawmidi private_free is set up to release the
> resources, but what concerns me is that at the moment of endpoint/port
> creation umidi is not yet added to the midi_list.
> In other words, what I see is that we still have just one local
> pointer to umidi if any of snd_usbmidi_create_endpoint* fail.

The snd_rawmidi device is automatically registered with the card, so the
line "rmidi->private_free = snd_usbmidi_rawmidi_free;" is the exact point
where the ownership of umidi changes.  midi_list does not matter.


Regards,
Clemens
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