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Reply-To: sedat.dilek@gmail.com
From:   Sedat Dilek <sedat.dilek@gmail.com>
Date:   Wed, 24 Feb 2021 19:08:59 +0100
Message-ID: <CA+icZUW=GTV0L884wdohaOdFmg4E4wdtSEOgF+KEGPcKzYOoow@mail.gmail.com>
Subject: Re: [PATCH] qemu_fw_cfg: Make fw_cfg_rev_attr a proper kobj_attribute
To:     Sami Tolvanen <samitolvanen@google.com>
Cc:     Nathan Chancellor <nathan@kernel.org>,
        Gabriel Somlo <somlo@cmu.edu>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Kees Cook <keescook@chromium.org>, qemu-devel@nongnu.org,
        LKML <linux-kernel@vger.kernel.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>
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On Thu, Feb 11, 2021 at 9:41 PM 'Sami Tolvanen' via Clang Built Linux
<clang-built-linux@googlegroups.com> wrote:
>
> Hi Nathan,
>
> On Thu, Feb 11, 2021 at 11:43 AM Nathan Chancellor <nathan@kernel.org> wrote:
> >
> > fw_cfg_showrev() is called by an indirect call in kobj_attr_show(),
> > which violates clang's CFI checking because fw_cfg_showrev()'s second
> > parameter is 'struct attribute', whereas the ->show() member of 'struct
> > kobj_structure' expects the second parameter to be of type 'struct
> > kobj_attribute'.
> >
> > $ cat /sys/firmware/qemu_fw_cfg/rev
> > 3
> >
> > $ dmesg | grep "CFI failure"
> > [   26.016832] CFI failure (target: fw_cfg_showrev+0x0/0x8):
> >
> > Fix this by converting fw_cfg_rev_attr to 'struct kobj_attribute' where
> > this would have been caught automatically by the incompatible pointer
> > types compiler warning. Update fw_cfg_showrev() accordingly.
> >
> > Fixes: 75f3e8e47f38 ("firmware: introduce sysfs driver for QEMU's fw_cfg device")
> > Link: https://github.com/ClangBuiltLinux/linux/issues/1299
> > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
>
> Looks good to me. Thank you for sending the patch!
>
> Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
>

Environment: Linux v5.11-10201-gc03c21ba6f4e plus Clang-CFI as of
24-Feb-2021 on top built with LLVM v13-git.

Tested-by: Sedat Dilek <sedat.dilek@gmail.com>

- Sedat -