linux-kernel - Re: [PATCH v2 00/11] getting back -Wmaybe-uninitialized

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Message-ID: <20161113084741.GA5225@kroah.com>
Date:   Sun, 13 Nov 2016 09:47:41 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        sayli karnik <karniksayli1995@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Anna Schumaker <anna.schumaker@...app.com>,
        "David S. Miller" <davem@...emloft.net>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Ilya Dryomov <idryomov@...il.com>,
        Javier Martinez Canillas <javier@....samsung.com>,
        Jiri Kosina <jikos@...nel.org>,
        Ley Foon Tan <lftan@...era.com>,
        "Luis R . Rodriguez" <mcgrof@...nel.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Michal Marek <mmarek@...e.com>,
        Russell King <linux@...linux.org.uk>,
        Sean Young <sean@...s.org>,
        Sebastian Ott <sebott@...ux.vnet.ibm.com>,
        Trond Myklebust <trond.myklebust@...marydata.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        arcml <linux-snps-arc@...ts.infradead.org>,
        nios2-dev@...ts.rocketboards.org,
        linux-s390 <linux-s390@...r.kernel.org>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Linux NFS Mailing List <linux-nfs@...r.kernel.org>
Subject: Re: [PATCH v2 00/11] getting back -Wmaybe-uninitialized

On Sat, Nov 12, 2016 at 01:27:12PM +0000, Jonathan Cameron wrote:
> On 11/11/16 19:49, Arnd Bergmann wrote:
> > On Friday, November 11, 2016 9:13:00 AM CET Linus Torvalds wrote:
> >> On Thu, Nov 10, 2016 at 8:44 AM, Arnd Bergmann <arnd@...db.de> wrote:
> >>>
> >>> Please merge these directly if you are happy with the result.
> >>
> >> I will take this.
> > 
> > Thanks a lot!
> >  
> >> I do see two warnings, but they both seem to be valid and recent,
> >> though, so I have no issues with the spurious cases.
> > 
> > Ok, both of them should have my fixes coming your way already.
> > 
> >> Warning #1:
> >>
> >>   sound/soc/qcom/lpass-platform.c: In function ‘lpass_platform_pcmops_open’:
> >>   sound/soc/qcom/lpass-platform.c:83:29: warning: ‘dma_ch’ may be used
> >> uninitialized in this function [-Wmaybe-uninitialized]
> >>     drvdata->substream[dma_ch] = substream;
> >>     ~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
> >>
> >> and 'dma_ch' usage there really is crazy and wrong. Broken by
> >> 022d00ee0b55 ("ASoC: lpass-platform: Fix broken pcm data usage")
> > 
> > Right, the patches crossed here, the bugfix patch that introduced
> > this came into linux-next over the kernel summit, and the fix I
> > sent on Tuesday made it into Mark Brown's tree on Wednesday but not
> > before you pulled alsa tree. It should be fixed the next time you
> > pull from the alsa tree, the commit is
> > 
> > 3b89e4b77ef9 ("ASoC: lpass-platform: initialize dma channel number")
> >  
> >> Warning #2 is not a real bug, but it's reasonable that gcc doesn't
> >> know that storage_bytes (chip->read_size) has to be 2/4. Again,
> >> introduced recently by commit 231147ee77f3 ("iio: maxim_thermocouple:
> >> Align 16 bit big endian value of raw reads"), so you didn't see it.
> > 
> > This is the one I mentioned in the commit message as one that
> > is fixed in linux-next and that should make it in soon.
> > 
> >>   drivers/iio/temperature/maxim_thermocouple.c: In function
> >> ‘maxim_thermocouple_read_raw’:
> >>   drivers/iio/temperature/maxim_thermocouple.c:141:5: warning: ‘ret’
> >> may be used uninitialized in this function [-Wmaybe-uninitialized]
> >>     if (ret)
> >>        ^
> >>   drivers/iio/temperature/maxim_thermocouple.c:128:6: note: ‘ret’ was
> >> declared here
> >>     int ret;
> >>         ^~~
> >>
> >> and I guess that code can just initialize 'ret' to '-EINVAL' or
> >> something to just make the theoretical "somehow we had a wrong
> >> chip->read_size" case error out cleanly.
> > 
> > Right, that was my conclusion too. I sent the bugfix on Oct 25
> > for linux-next but it didn't make it in until this Monday, after
> > you pulled the patch that introduced it on Oct 29.
> > 
> > The commit in staging-testing is
> > 32cb7d27e65d ("iio: maxim_thermocouple: detect invalid storage size in read()")
> > 
> > Greg and Jonathan, I see now that this is part of the 'iio-for-4.10b'
> > branch, so I suspect you were not planning to send this before the
> > merge window. Could you make sure this ends up in v4.9 so we get
> > a clean build when -Wmaybe-uninitialized gets enabled again?
> I'll queue this up and send a pull to Greg tomorrow.
> 
> Was highly doubtful that a false warning suppression (be it an
> understandable one) was worth sending mid cycle, hence it was
> taking the slow route.

I can just cherry-pick this, no need to send a separate pull request.

greg k-h