linux-kernel - Re: [PATCH] ALSA: virtio: Fix "Coverity: virtsnd_kctl_tlv

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Message-ID:
 <FR3P281MB2527A0498C3B1E3899087028E64E2@FR3P281MB2527.DEUP281.PROD.OUTLOOK.COM>
Date: Wed, 14 Feb 2024 13:07:40 +0000
From: Aiswarya Cyriac <Aiswarya.Cyriac@...nsynergy.com>
To: Takashi Iwai <tiwai@...e.de>, "Michael S. Tsirkin" <mst@...hat.com>
CC: "jasowang@...hat.com" <jasowang@...hat.com>, "perex@...ex.cz"
	<perex@...ex.cz>, "tiwai@...e.com" <tiwai@...e.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"virtualization@...ts.linux-foundation.org"
	<virtualization@...ts.linux-foundation.org>,
	"virtio-dev@...ts.oasis-open.org" <virtio-dev@...ts.oasis-open.org>, Anton
 Yakovlev <Anton.Yakovlev@...nsynergy.com>, coverity-bot
	<keescook+coverity-bot@...omium.org>, Mikhail Golubev-Ciuchea
	<Mikhail.Golubev-Ciuchea@...nsynergy.com>
Subject: Re: [PATCH] ALSA: virtio: Fix "Coverity: virtsnd_kctl_tlv_op():
 Uninitialized variables" warning.


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@...nsynergy.com>
>> > >> Signed-off-by: Aiswarya Cyriac <aiswarya.cyriac@...nsynergy.com>
>> > >> Reported-by: coverity-bot <keescook+coverity-bot@...omium.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?