Re: drivers/platform/surface/surface3-wmi.c:60:14: warning: variable 'status' set but not used

[Maximilian Luz]

On 2/4/21 12:36 PM, Hans de Goede wrote:
> Hi,
>
> On 1/4/21 4:24 PM, Maximilian Luz wrote:
> > On 1/4/21 3:52 PM, Hans de Goede wrote:
> > > Hi,
> > >
> > > On 12/29/20 4:58 AM, kernel test robot wrote:
> > > > Hi Maximilian,
> > > >
> > > > FYI, the error/warning still remains.
> > > >
> > > > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > > > head:   dea8dcf2a9fa8cc540136a6cd885c3beece16ec3
> > > > commit: f23027ca3d48b6f93c5994069fb25b73539fdf34 platform/surface: Move Surface 3 WMI driver to platform/surface
> > > > date:   9 weeks ago
> > > > config: x86_64-randconfig-r001-20201221 (attached as .config)
> > > > compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
> > > > reproduce (this is a W=1 build):
> > > >           # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f23027ca3d48b6f93c5994069fb25b73539fdf34
> > > >           git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> > > >           git fetch --no-tags linus master
> > > >           git checkout f23027ca3d48b6f93c5994069fb25b73539fdf34
> > > >           # save the attached .config to linux build tree
> > > >           make W=1 ARCH=x86_64
> > > >
> > > > If you fix the issue, kindly add following tag as appropriate
> > > > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > > >
> > > > All warnings (new ones prefixed by >>):
> > > >
> > > >      drivers/platform/surface/surface3-wmi.c: In function 's3_wmi_query_block':
> > > > > > drivers/platform/surface/surface3-wmi.c:60:14: warning: variable 'status' set but not used [-Wunused-but-set-variable]
> > > >         60 |  acpi_status status;
> > > >            |              ^~~~~~
> > >
> > > I guess fixing this would require something like this:
> > >
> > > From: Hans de Goede <hdegoede@xxxxxxxxxx>
> > > Subject: [PATCH] platform/surface: surface3-wmi: Fix variable 'status' set but not used compiler warning
> > >
> > > Explictly check the status rather then relying on output.pointer staying
> > > NULL on an error. This silences the following compiler warning:
> > >
> > > drivers/platform/surface/surface3-wmi.c:60:14: warning: variable 'status' set but not used [-Wunused-but-set-variable]
> > >
> > > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > > Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> > > ---
> > >    drivers/platform/surface/surface3-wmi.c | 4 ++++
> > >    1 file changed, 4 insertions(+)
> > >
> > > diff --git a/drivers/platform/surface/surface3-wmi.c b/drivers/platform/surface/surface3-wmi.c
> > > index 130b6f52a600..4b7f79c0b78e 100644
> > > --- a/drivers/platform/surface/surface3-wmi.c
> > > +++ b/drivers/platform/surface/surface3-wmi.c
> > > @@ -63,6 +63,10 @@ static int s3_wmi_query_block(const char *guid, int instance, int *ret)
> > >          mutex_lock(&s3_wmi_lock);
> > >        status = wmi_query_block(guid, instance, &output);
> > > +    if (ACPI_FAILURE(status)) {
> > > +        error = -EIO;
> > > +        goto out_free_unlock;
> > > +    }
> > >          obj = output.pointer;
> > >   
> > > Maximilian, can you review and/or test this fix please ?
> >
> > Ah, this was on my TODO list (among looking at some other things in this
> > driver), sorry that I haven't gotten to it yet. I'd have proposed pretty
> > much the exact same thing.
> >
> > One thing to note though: You should initialize obj with NULL. Keeping
> > it uninitialized may mess with kfree() under out_free_unlock.
> >
> > Unfortunately I don't have access to a Surface 3 to test, but apart from
> > not initializing obj, this patch looks good to me. You may add my
> > reviewed-by tag once you've fixed that.
>
> Thank you, and sorry for being a bit slow with my follow up.

No worries.
 
> I've added the obj = NULL initialization and added your reviewed-by tag.
>
> I'm sending this out as an official patch submission for the archives now
> and then I'll apply it to my review-hans branch right away, so no need
> for you to do anything :)
>
> > Also note that drivers/platform/x86/msi-wmi.c suffers from the same
> > problem in msi_wmi_query_block() and should receive a similar fix.
>
> Thanks, I'll prep a patch for that too.

Perfect, thanks!

Regards,
Max

> Regards,
>
> Hans