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:

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On Wed, Feb 14, 2024 at 09:08:26AM +0000, Aiswarya Cyriac wrote:

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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:

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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 <redacted>
Reported-by: coverity-bot <redacted>
Addresses-Coverity-ID: 1583619 ("Uninitialized variables")
Fixes: d6568e3de42d ("ALSA: virtio: add support for audio controls")

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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?