ALSA: virtio: Fix "Coverity: virtsnd_kctl_tlv_op(): Uninitialized variables" warning.

  Fix the following warning when building virtio_snd driver.

"
*** CID 1583619:  Uninitialized variables  (UNINIT)
sound/virtio/virtio_kctl.c:294 in virtsnd_kctl_tlv_op()
288
289         break;
290       }
291
292       kfree(tlv);
293
vvv     CID 1583619:  Uninitialized variables  (UNINIT)
vvv     Using uninitialized value "rc".
294       return rc;
295     }
296
297     /**
298      * virtsnd_kctl_get_enum_items() - Query items for the ENUMERATED element type.
299      * @snd: VirtIO sound device.
"

Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com>
Signed-off-by: Aiswarya Cyriac <aiswarya.cyriac@opensynergy.com>
Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
Addresses-Coverity-ID: 1583619 ("Uninitialized variables")
Fixes: d6568e3de42d ("ALSA: virtio: add support for audio controls")
---
 sound/virtio/virtio_kctl.c | 5 +++++
 1 file changed, 5 insertions(+)
  

On Tue, 13 Feb 2024 10:07:35 +0100,
Michael S. Tsirkin wrote:
> 
> On Tue, Feb 13, 2024 at 10:02:24AM +0100, Takashi Iwai wrote:
> > On Tue, 13 Feb 2024 09:51:30 +0100,
> > Aiswarya Cyriac wrote:
> > > 
> > > Fix the following warning when building virtio_snd driver.
> > > 
> > > "
> > > *** CID 1583619:  Uninitialized variables  (UNINIT)
> > > sound/virtio/virtio_kctl.c:294 in virtsnd_kctl_tlv_op()
> > > 288
> > > 289         break;
> > > 290       }
> > > 291
> > > 292       kfree(tlv);
> > > 293
> > > vvv     CID 1583619:  Uninitialized variables  (UNINIT)
> > > vvv     Using uninitialized value "rc".
> > > 294       return rc;
> > > 295     }
> > > 296
> > > 297     /**
> > > 298      * virtsnd_kctl_get_enum_items() - Query items for the ENUMERATED element type.
> > > 299      * @snd: VirtIO sound device.
> > > "
> > > 
> > > Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com>
> > > Signed-off-by: Aiswarya Cyriac <aiswarya.cyriac@opensynergy.com>
> > > Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
> > > Addresses-Coverity-ID: 1583619 ("Uninitialized variables")
> > > Fixes: d6568e3de42d ("ALSA: virtio: add support for audio controls")
> > 
> > Thanks, applied.
> > 
> > 
> > Takashi
> 
> Why did you apply it directly? The patch isn't great IMHO.
> Why not give people a couple of days to review?

Sure, we can wait.  I applied it quickly just since it's an obvious
fix and you haven't responded to the original patch over a month.


thanks,

Takashi
  

Hi Michael,

Thank you for reviewing. I have updated my response inline

On Tue, Feb 13, 2024 at 09:51:30AM +0100, Aiswarya Cyriac wrote:
>> Fix the following warning when building virtio_snd driver.
>>
>> "
>> *** CID 1583619:  Uninitialized variables  (UNINIT)
>> sound/virtio/virtio_kctl.c:294 in virtsnd_kctl_tlv_op()
>> 288
>> 289         break;
>> 290       }
>> 291
>> 292       kfree(tlv);
>> 293
>> vvv     CID 1583619:  Uninitialized variables  (UNINIT)
>> vvv     Using uninitialized value "rc".
>> 294       return rc;
>> 295     }
>> 296
>> 297     /**
>> 298      * virtsnd_kctl_get_enum_items() - Query items for the ENUMERATED element type.
>> 299      * @snd: VirtIO sound device.
>> "
>>
>> Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com>
>> Signed-off-by: Aiswarya Cyriac <aiswarya.cyriac@opensynergy.com>
>> Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
>> Addresses-Coverity-ID: 1583619 ("Uninitialized variables")
>> Fixes: d6568e3de42d ("ALSA: virtio: add support for audio controls")

>I don't know enough about ALSA to say whether the patch is correct.  But
>the commit log needs work: please, do not "fix warnings" - analyse the
>code and explain whether there is a real issue and if yes what is it
>and how it can trigger. Is an invalid op_flag ever passed?
>If it's just a coverity false positive it might be ok to
>work around that but document this.

This warning is caused by the absence of the "default" branch in the
switch-block, and is a false positive because the kernel calls
virtsnd_kctl_tlv_op() only with values for op_flag processed in
this block.
I will update the fix and send a v2 patch

>> ---
>>  sound/virtio/virtio_kctl.c | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/sound/virtio/virtio_kctl.c b/sound/virtio/virtio_kctl.c
>> index 0c6ac74aca1e..d7a160c5db03 100644
>> --- a/sound/virtio/virtio_kctl.c
>> +++ b/sound/virtio/virtio_kctl.c
>> @@ -286,6 +286,11 @@ static int virtsnd_kctl_tlv_op(struct snd_kcontrol *kcontrol, int op_flag,
>>                else
>>                        rc = virtsnd_ctl_msg_send(snd, msg, &sg, NULL, false);
>>
>> +             break;
>> +     default:
>> +             virtsnd_ctl_msg_unref(msg);
>> +             rc = -EINVAL;
>> +

>There's already virtsnd_ctl_msg_unref call above.
>Also don't we need virtsnd_ctl_msg_unref on other error paths
>such as EFAULT?
>Unify error handling to fix it all then?

This also need to be handled and virtsnd_ctl_msg_unref needed in case of EFAULT as well.
I will update the patch.


Thanks,
Aiswarya Cyriac
Software Engineer
​
OpenSynergy GmbH
Rotherstr. 20, 10245 Berlin

EMail: aiswarya.cyriac@opensynergy.com

www.opensynergy.com
Handelsregister/Commercial Registry: Amtsgericht Charlottenburg, HRB 108616B
Geschäftsführer/Managing Director: Régis Adjamah

________________________________________
From: Michael S. Tsirkin <mst@redhat.com>
Sent: Tuesday, February 13, 2024 10:06 AM
To: Aiswarya Cyriac
Cc: jasowang@redhat.com; perex@perex.cz; tiwai@suse.com; linux-kernel@vger.kernel.org; alsa-devel@alsa-project.org; virtualization@lists.linux-foundation.org; virtio-dev@lists.oasis-open.org; Anton Yakovlev; coverity-bot
Subject: Re: [PATCH] ALSA: virtio: Fix "Coverity: virtsnd_kctl_tlv_op(): Uninitialized variables" warning.

On Tue, Feb 13, 2024 at 09:51:30AM +0100, Aiswarya Cyriac wrote:
> Fix the following warning when building virtio_snd driver.
>
> "
> *** CID 1583619:  Uninitialized variables  (UNINIT)
> sound/virtio/virtio_kctl.c:294 in virtsnd_kctl_tlv_op()
> 288
> 289         break;
> 290       }
> 291
> 292       kfree(tlv);
> 293
> vvv     CID 1583619:  Uninitialized variables  (UNINIT)
> vvv     Using uninitialized value "rc".
> 294       return rc;
> 295     }
> 296
> 297     /**
> 298      * virtsnd_kctl_get_enum_items() - Query items for the ENUMERATED element type.
> 299      * @snd: VirtIO sound device.
> "
>
> Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com>
> Signed-off-by: Aiswarya Cyriac <aiswarya.cyriac@opensynergy.com>
> Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
> Addresses-Coverity-ID: 1583619 ("Uninitialized variables")
> Fixes: d6568e3de42d ("ALSA: virtio: add support for audio controls")

I don't know enough about ALSA to say whether the patch is correct.  But
the commit log needs work: please, do not "fix warnings" - analyse the
code and explain whether there is a real issue and if yes what is it
and how it can trigger. Is an invalid op_flag ever passed?
If it's just a coverity false positive it might be ok to
work around that but document this.


> ---
>  sound/virtio/virtio_kctl.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/sound/virtio/virtio_kctl.c b/sound/virtio/virtio_kctl.c
> index 0c6ac74aca1e..d7a160c5db03 100644
> --- a/sound/virtio/virtio_kctl.c
> +++ b/sound/virtio/virtio_kctl.c
> @@ -286,6 +286,11 @@ static int virtsnd_kctl_tlv_op(struct snd_kcontrol *kcontrol, int op_flag,
>               else
>                       rc = virtsnd_ctl_msg_send(snd, msg, &sg, NULL, false);
>
> +             break;
> +     default:
> +             virtsnd_ctl_msg_unref(msg);
> +             rc = -EINVAL;
> +

There's already virtsnd_ctl_msg_unref call above.
Also don't we need virtsnd_ctl_msg_unref on other error paths
such as EFAULT?
Unify error handling to fix it all then?

>               break;
>       }
>
> --
> 2.43.0
  

On Wed, Feb 14, 2024 at 09:08:26AM +0000, Aiswarya Cyriac wrote:
> Hi Michael,
> 
> Thank you for reviewing. I have updated my response inline
> 
> On Tue, Feb 13, 2024 at 09:51:30AM +0100, Aiswarya Cyriac wrote:
> >> Fix the following warning when building virtio_snd driver.
> >>
> >> "
> >> *** CID 1583619:  Uninitialized variables  (UNINIT)
> >> sound/virtio/virtio_kctl.c:294 in virtsnd_kctl_tlv_op()
> >> 288
> >> 289         break;
> >> 290       }
> >> 291
> >> 292       kfree(tlv);
> >> 293
> >> vvv     CID 1583619:  Uninitialized variables  (UNINIT)
> >> vvv     Using uninitialized value "rc".
> >> 294       return rc;
> >> 295     }
> >> 296
> >> 297     /**
> >> 298      * virtsnd_kctl_get_enum_items() - Query items for the ENUMERATED element type.
> >> 299      * @snd: VirtIO sound device.
> >> "
> >>
> >> Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com>
> >> Signed-off-by: Aiswarya Cyriac <aiswarya.cyriac@opensynergy.com>
> >> Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
> >> Addresses-Coverity-ID: 1583619 ("Uninitialized variables")
> >> Fixes: d6568e3de42d ("ALSA: virtio: add support for audio controls")
> 
> >I don't know enough about ALSA to say whether the patch is correct.  But
> >the commit log needs work: please, do not "fix warnings" - analyse the
> >code and explain whether there is a real issue and if yes what is it
> >and how it can trigger. Is an invalid op_flag ever passed?
> >If it's just a coverity false positive it might be ok to
> >work around that but document this.
> 
> This warning is caused by the absence of the "default" branch in the
> switch-block, and is a false positive because the kernel calls
> virtsnd_kctl_tlv_op() only with values for op_flag processed in
> this block.

Well we don't normally have functions validate inputs.
In this case I am not really sure we should bother
with adding dead code. If you really want to, add BUG_ON.



> I will update the fix and send a v2 patch
> 
> >> ---
> >>  sound/virtio/virtio_kctl.c | 5 +++++
> >>  1 file changed, 5 insertions(+)
> >>
> >> diff --git a/sound/virtio/virtio_kctl.c b/sound/virtio/virtio_kctl.c
> >> index 0c6ac74aca1e..d7a160c5db03 100644
> >> --- a/sound/virtio/virtio_kctl.c
> >> +++ b/sound/virtio/virtio_kctl.c
> >> @@ -286,6 +286,11 @@ static int virtsnd_kctl_tlv_op(struct snd_kcontrol *kcontrol, int op_flag,
> >>                else
> >>                        rc = virtsnd_ctl_msg_send(snd, msg, &sg, NULL, false);
> >>
> >> +             break;
> >> +     default:
> >> +             virtsnd_ctl_msg_unref(msg);
> >> +             rc = -EINVAL;
> >> +
> 
> >There's already virtsnd_ctl_msg_unref call above.
> >Also don't we need virtsnd_ctl_msg_unref on other error paths
> >such as EFAULT?
> >Unify error handling to fix it all then?
> 
> This also need to be handled and virtsnd_ctl_msg_unref needed in case of EFAULT as well.
> I will update the patch.
> 
> 
> Thanks,
> Aiswarya Cyriac
> Software Engineer
> ​
> OpenSynergy GmbH
> Rotherstr. 20, 10245 Berlin
> 
> EMail: aiswarya.cyriac@opensynergy.com
> 
> www.opensynergy.com
> Handelsregister/Commercial Registry: Amtsgericht Charlottenburg, HRB 108616B
> Geschäftsführer/Managing Director: Régis Adjamah
> 
> ________________________________________
> From: Michael S. Tsirkin <mst@redhat.com>
> Sent: Tuesday, February 13, 2024 10:06 AM
> To: Aiswarya Cyriac
> Cc: jasowang@redhat.com; perex@perex.cz; tiwai@suse.com; linux-kernel@vger.kernel.org; alsa-devel@alsa-project.org; virtualization@lists.linux-foundation.org; virtio-dev@lists.oasis-open.org; Anton Yakovlev; coverity-bot
> Subject: Re: [PATCH] ALSA: virtio: Fix "Coverity: virtsnd_kctl_tlv_op(): Uninitialized variables" warning.
> 
> On Tue, Feb 13, 2024 at 09:51:30AM +0100, Aiswarya Cyriac wrote:
> > Fix the following warning when building virtio_snd driver.
> >
> > "
> > *** CID 1583619:  Uninitialized variables  (UNINIT)
> > sound/virtio/virtio_kctl.c:294 in virtsnd_kctl_tlv_op()
> > 288
> > 289         break;
> > 290       }
> > 291
> > 292       kfree(tlv);
> > 293
> > vvv     CID 1583619:  Uninitialized variables  (UNINIT)
> > vvv     Using uninitialized value "rc".
> > 294       return rc;
> > 295     }
> > 296
> > 297     /**
> > 298      * virtsnd_kctl_get_enum_items() - Query items for the ENUMERATED element type.
> > 299      * @snd: VirtIO sound device.
> > "
> >
> > Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com>
> > Signed-off-by: Aiswarya Cyriac <aiswarya.cyriac@opensynergy.com>
> > Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
> > Addresses-Coverity-ID: 1583619 ("Uninitialized variables")
> > Fixes: d6568e3de42d ("ALSA: virtio: add support for audio controls")
> 
> I don't know enough about ALSA to say whether the patch is correct.  But
> the commit log needs work: please, do not "fix warnings" - analyse the
> code and explain whether there is a real issue and if yes what is it
> and how it can trigger. Is an invalid op_flag ever passed?
> If it's just a coverity false positive it might be ok to
> work around that but document this.
> 
> 
> > ---
> >  sound/virtio/virtio_kctl.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/sound/virtio/virtio_kctl.c b/sound/virtio/virtio_kctl.c
> > index 0c6ac74aca1e..d7a160c5db03 100644
> > --- a/sound/virtio/virtio_kctl.c
> > +++ b/sound/virtio/virtio_kctl.c
> > @@ -286,6 +286,11 @@ static int virtsnd_kctl_tlv_op(struct snd_kcontrol *kcontrol, int op_flag,
> >               else
> >                       rc = virtsnd_ctl_msg_send(snd, msg, &sg, NULL, false);
> >
> > +             break;
> > +     default:
> > +             virtsnd_ctl_msg_unref(msg);
> > +             rc = -EINVAL;
> > +
> 
> There's already virtsnd_ctl_msg_unref call above.
> Also don't we need virtsnd_ctl_msg_unref on other error paths
> such as EFAULT?
> Unify error handling to fix it all then?
> 
> >               break;
> >       }
> >
> > --
> > 2.43.0
> 
>
  

On Wed, 14 Feb 2024 12:30:19 +0100,
Michael S. Tsirkin wrote:
> 
> On Wed, Feb 14, 2024 at 09:08:26AM +0000, Aiswarya Cyriac wrote:
> > Hi Michael,
> > 
> > Thank you for reviewing. I have updated my response inline
> > 
> > On Tue, Feb 13, 2024 at 09:51:30AM +0100, Aiswarya Cyriac wrote:
> > >> Fix the following warning when building virtio_snd driver.
> > >>
> > >> "
> > >> *** CID 1583619:  Uninitialized variables  (UNINIT)
> > >> sound/virtio/virtio_kctl.c:294 in virtsnd_kctl_tlv_op()
> > >> 288
> > >> 289         break;
> > >> 290       }
> > >> 291
> > >> 292       kfree(tlv);
> > >> 293
> > >> vvv     CID 1583619:  Uninitialized variables  (UNINIT)
> > >> vvv     Using uninitialized value "rc".
> > >> 294       return rc;
> > >> 295     }
> > >> 296
> > >> 297     /**
> > >> 298      * virtsnd_kctl_get_enum_items() - Query items for the ENUMERATED element type.
> > >> 299      * @snd: VirtIO sound device.
> > >> "
> > >>
> > >> Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com>
> > >> Signed-off-by: Aiswarya Cyriac <aiswarya.cyriac@opensynergy.com>
> > >> Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
> > >> Addresses-Coverity-ID: 1583619 ("Uninitialized variables")
> > >> Fixes: d6568e3de42d ("ALSA: virtio: add support for audio controls")
> > 
> > >I don't know enough about ALSA to say whether the patch is correct.  But
> > >the commit log needs work: please, do not "fix warnings" - analyse the
> > >code and explain whether there is a real issue and if yes what is it
> > >and how it can trigger. Is an invalid op_flag ever passed?
> > >If it's just a coverity false positive it might be ok to
> > >work around that but document this.
> > 
> > This warning is caused by the absence of the "default" branch in the
> > switch-block, and is a false positive because the kernel calls
> > virtsnd_kctl_tlv_op() only with values for op_flag processed in
> > this block.
> 
> Well we don't normally have functions validate inputs.
> In this case I am not really sure we should bother
> with adding dead code. If you really want to, add BUG_ON.

Please don't use BUG_ON() in such a case...
There is no reason to break the whole operation.


thanks,

Takashi
  

On Wed, 14 Feb 2024 12:30:19 +0100,
Michael S. Tsirkin wrote:
>>
>> On Wed, Feb 14, 2024 at 09:08:26AM +0000, Aiswarya Cyriac wrote:
>> > Hi Michael,
>> >
>> > Thank you for reviewing. I have updated my response inline
>> >
>> > On Tue, Feb 13, 2024 at 09:51:30AM +0100, Aiswarya Cyriac wrote:
>> > >> Fix the following warning when building virtio_snd driver.
>> > >>
>> > >> "
>> > >> *** CID 1583619:  Uninitialized variables  (UNINIT)
>> > >> sound/virtio/virtio_kctl.c:294 in virtsnd_kctl_tlv_op()
>> > >> 288
>> > >> 289         break;
>> > >> 290       }
>> > >> 291
>> > >> 292       kfree(tlv);
>> > >> 293
>> > >> vvv     CID 1583619:  Uninitialized variables  (UNINIT)
>> > >> vvv     Using uninitialized value "rc".
>> > >> 294       return rc;
>> > >> 295     }
>> > >> 296
>> > >> 297     /**
>> > >> 298      * virtsnd_kctl_get_enum_items() - Query items for the ENUMERATED element type.
>> > >> 299      * @snd: VirtIO sound device.
>> > >> "
>> > >>
>> > >> Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com>
>> > >> Signed-off-by: Aiswarya Cyriac <aiswarya.cyriac@opensynergy.com>
>> > >> Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
>> > >> Addresses-Coverity-ID: 1583619 ("Uninitialized variables")
>> > >> Fixes: d6568e3de42d ("ALSA: virtio: add support for audio controls")
>> >
>> > >I don't know enough about ALSA to say whether the patch is correct.  But
>> > >the commit log needs work: please, do not "fix warnings" - analyse the
>> > >code and explain whether there is a real issue and if yes what is it
>> > >and how it can trigger. Is an invalid op_flag ever passed?
>> > >If it's just a coverity false positive it might be ok to
>> > >work around that but document this.
>> >
>> > This warning is caused by the absence of the "default" branch in the
>> > switch-block, and is a false positive because the kernel calls
>> > virtsnd_kctl_tlv_op() only with values for op_flag processed in
>> > this block.
>>
>> Well we don't normally have functions validate inputs.
>> In this case I am not really sure we should bother
>> with adding dead code. If you really want to, add BUG_ON.

> Please don't use BUG_ON() in such a case...
> There is no reason to break the whole operation.

How about adding a WARN_ON() on default case?
  

On Wed, 14 Feb 2024 14:07:40 +0100,
Aiswarya Cyriac wrote:
> 
> 
> On Wed, 14 Feb 2024 12:30:19 +0100,
> Michael S. Tsirkin wrote:
> >>
> >> On Wed, Feb 14, 2024 at 09:08:26AM +0000, Aiswarya Cyriac wrote:
> >> > Hi Michael,
> >> >
> >> > Thank you for reviewing. I have updated my response inline
> >> >
> >> > On Tue, Feb 13, 2024 at 09:51:30AM +0100, Aiswarya Cyriac wrote:
> >> > >> Fix the following warning when building virtio_snd driver.
> >> > >>
> >> > >> "
> >> > >> *** CID 1583619:  Uninitialized variables  (UNINIT)
> >> > >> sound/virtio/virtio_kctl.c:294 in virtsnd_kctl_tlv_op()
> >> > >> 288
> >> > >> 289         break;
> >> > >> 290       }
> >> > >> 291
> >> > >> 292       kfree(tlv);
> >> > >> 293
> >> > >> vvv     CID 1583619:  Uninitialized variables  (UNINIT)
> >> > >> vvv     Using uninitialized value "rc".
> >> > >> 294       return rc;
> >> > >> 295     }
> >> > >> 296
> >> > >> 297     /**
> >> > >> 298      * virtsnd_kctl_get_enum_items() - Query items for the ENUMERATED element type.
> >> > >> 299      * @snd: VirtIO sound device.
> >> > >> "
> >> > >>
> >> > >> Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com>
> >> > >> Signed-off-by: Aiswarya Cyriac <aiswarya.cyriac@opensynergy.com>
> >> > >> Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
> >> > >> Addresses-Coverity-ID: 1583619 ("Uninitialized variables")
> >> > >> Fixes: d6568e3de42d ("ALSA: virtio: add support for audio controls")
> >> >
> >> > >I don't know enough about ALSA to say whether the patch is correct.  But
> >> > >the commit log needs work: please, do not "fix warnings" - analyse the
> >> > >code and explain whether there is a real issue and if yes what is it
> >> > >and how it can trigger. Is an invalid op_flag ever passed?
> >> > >If it's just a coverity false positive it might be ok to
> >> > >work around that but document this.
> >> >
> >> > This warning is caused by the absence of the "default" branch in the
> >> > switch-block, and is a false positive because the kernel calls
> >> > virtsnd_kctl_tlv_op() only with values for op_flag processed in
> >> > this block.
> >>
> >> Well we don't normally have functions validate inputs.
> >> In this case I am not really sure we should bother
> >> with adding dead code. If you really want to, add BUG_ON.
> 
> > Please don't use BUG_ON() in such a case...
> > There is no reason to break the whole operation.
> 
> How about adding a WARN_ON() on default case?

That's better :)


thanks,

Takashi