linux-kernel - Re: [PATCH v2 10/16] KVM: PPC: Book3S PR: Remove uninitialized

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Message-ID: <CAKwvOd=N3HQNZfKMQ7eZWdawwNn13=YNNgMO0WAng2ERYX4Juw@mail.gmail.com>
Date:   Mon, 22 Jun 2020 10:22:53 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Joe Perches <joe@...ches.com>,
        Andy Whitcroft <apw@...onical.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        drbd-dev@...ts.linbit.com, linux-block@...r.kernel.org,
        b43-dev@...ts.infradead.org,
        Network Development <netdev@...r.kernel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        linux-ide@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-spi@...r.kernel.org,
        Linux Memory Management List <linux-mm@...ck.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH v2 10/16] KVM: PPC: Book3S PR: Remove uninitialized_var() usage

On Fri, Jun 19, 2020 at 8:30 PM Kees Cook <keescook@...omium.org> wrote:
>
> Using uninitialized_var() is dangerous as it papers over real bugs[1]
> (or can in the future), and suppresses unrelated compiler warnings (e.g.
> "unused variable"). If the compiler thinks it is uninitialized, either
> simply initialize the variable or make compiler changes. As a precursor
> to removing[2] this[3] macro[4], just remove this variable since it was
> actually unused:
>
> arch/powerpc/kvm/book3s_pr.c:1832:16: warning: unused variable 'vrsave' [-Wunused-variable]
>         unsigned long vrsave;
>                       ^
>
> [1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
> [2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
> [3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
> [4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/
>
> Suggested-by: Nathan Chancellor <natechancellor@...il.com>
> Fixes: f05ed4d56e9c ("KVM: PPC: Split out code from book3s.c into book3s_pr.c")
> Signed-off-by: Kees Cook <keescook@...omium.org>

Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

> ---
>  arch/powerpc/kvm/book3s_pr.c | 3 ---
>  1 file changed, 3 deletions(-)
>
> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
> index ef54f917bdaf..ed12dfbf9bb5 100644
> --- a/arch/powerpc/kvm/book3s_pr.c
> +++ b/arch/powerpc/kvm/book3s_pr.c
> @@ -1828,9 +1828,6 @@ static int kvmppc_vcpu_run_pr(struct kvm_vcpu *vcpu)
>  {
>         struct kvm_run *run = vcpu->run;
>         int ret;
> -#ifdef CONFIG_ALTIVEC
> -       unsigned long uninitialized_var(vrsave);
> -#endif
>
>         /* Check if we can run the vcpu at all */
>         if (!vcpu->arch.sane) {
> --

-- 
Thanks,
~Nick Desaulniers