[alsa-devel] SEGFault when optininal snd_ctl_ext_callback::read_event() not set

[Wischer, Timo (ADITG/ESB)]

Hi Takashi,

see attached the patch.
>From my opinion failing with an error is the best solution (see explanation in the commit message)


Best regards

Timo Wischer

Advanced Driver Information Technology GmbH
Engineering Software Base (ADITG/ESB)
Robert-Bosch-Str. 200
31139 Hildesheim
Germany

Tel. +49 5121 49 6938
Fax +49 5121 49 6999
twischer at de.adit-jv.com

ADIT is a joint venture company of Robert Bosch GmbH/Robert Bosch Car Multimedia GmbH and DENSO Corporation
Sitz: Hildesheim, Registergericht: Amtsgericht Hildesheim HRB 3438
Geschäftsführung: Wilhelm Grabow, Ken Yaguchi

________________________________________
From: Takashi Iwai [tiwai at suse.de]
Sent: Thursday, October 05, 2017 3:17 PM
To: Wischer, Timo (ADITG/ESB)
Cc: alsa-devel at alsa-project.org
Subject: Re: [alsa-devel] SEGFault when optininal       snd_ctl_ext_callback::read_event() not set

On Thu, 05 Oct 2017 14:03:14 +0200,
Wischer, Timo (ADITG/ESB) wrote:
>
> Hi all,
>
> snd_ctl_ext_callback::read_event() callback is mentioned as optional
> (see http://git.alsa-project.org/?p=alsa-lib.git;a=blob;f=include/control_external.h;h=12958e70a5230de9c74029c641a395a2073c8646;hb=refs/heads/master#l239)
>
> but there is no NULL check and the NULL pointer will be called if the read_event function callback pointer is not set.
> (see http://git.alsa-project.org/?p=alsa-lib.git;a=blob;f=src/control/control_ext.c;h=56552fa1aa0ef0e6383abf4029b63944a841c2c4;hb=refs/heads/master#l419)
>
> I think a default function has to be provided which will be called when the callback is not set or the read_event() callback should not be marked as optional.
>
> What is your opinion?

It should have a NULL check there, as documentation clearly states
that it's optional.

Care to submit a fix patch?


thanks,

Takashi
-------------- next part --------------
A non-text attachment was scrubbed...
Name: alsa-lib-ctl-ext-read-event.patch
Type: text/x-patch
Size: 1519 bytes
Desc: alsa-lib-ctl-ext-read-event.patch
URL: <http://mailman.alsa-project.org/pipermail/alsa-devel/attachments/20171005/437e613f/attachment.bin>