linux-kernel - Re: stable-rc 6.1: x86: clang build failed - block/blk-cgroup.c:1237:6: error: variable 'ret' is used uninitialized whenever 'if' condition is true

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Date:   Mon, 17 Jul 2023 20:47:17 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Naresh Kamboju <naresh.kamboju@...aro.org>,
        Sasha Levin <sashal@...nel.org>,
        linux-stable <stable@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        clang-built-linux <llvm@...ts.linux.dev>,
        lkft-triage@...ts.linaro.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Anders Roxell <anders.roxell@...aro.org>
Subject: Re: stable-rc 6.1: x86: clang build failed -
 block/blk-cgroup.c:1237:6: error: variable 'ret' is used uninitialized
 whenever 'if' condition is true

On Mon, Jul 17, 2023 at 06:24:26AM -0700, Nathan Chancellor wrote:
> On Mon, Jul 17, 2023 at 12:55:42AM +0530, Naresh Kamboju wrote:
> > Linux stable-rc 6.1 build failed x86 and i386 with clang.
> > 
> > Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>
> > 
> > Build log:
> > -----------
> > block/blk-cgroup.c:1237:6: error: variable 'ret' is used uninitialized
> > whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
> >         if (init_blkcg_llists(blkcg))
> >             ^~~~~~~~~~~~~~~~~~~~~~~~
> > block/blk-cgroup.c:1287:9: note: uninitialized use occurs here
> >         return ret;
> >                ^~~
> > block/blk-cgroup.c:1237:2: note: remove the 'if' if its condition is
> > always false
> >         if (init_blkcg_llists(blkcg))
> >         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > block/blk-cgroup.c:1222:33: note: initialize the variable 'ret' to
> > silence this warning
> >         struct cgroup_subsys_state *ret;
> >                                        ^
> >                                         = NULL
> > 1 error generated.
> > 
> > Links,
> >  - https://qa-reports.linaro.org/lkft/linux-stable-rc-linux-6.1.y-sanity/build/v6.1.38-599-g5071846d06ef/testrun/18327562/suite/build/test/clang-lkftconfig/history/
> >  - https://storage.tuxsuite.com/public/linaro/lkft/builds/2SfFoWj9NmKWHRijR0hcoXGjLhr/
> > 
> >  tuxmake \
> >  --runtime podman --target-arch x86_64 \
> >  --toolchain clang-16 \
> >  --kconfig https://storage.tuxsuite.com/public/linaro/lkft/builds/2SfFoWj9NmKWHRijR0hcoXGjLhr/config
> > \
> >  LLVM=1 LLVM_IAS=1
> > 
> 
> It looks like 6.1 needs commit b5a9adcbd5dc ("blk-cgroup: Return -ENOMEM
> directly in blkcg_css_alloc() error path") if it wants to take commit
> 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()").

I'm going to drop the offending patch now, thanks.

greg k-h