Re: [PATCH v2 10/16] KVM: PPC: Book3S PR: Remove uninitialized_var() usage

Nick Desaulniers
2020-06-22T17:23:09Z

On Fri, Jun 19, 2020 at 8:30 PM Kees Cook <keescook@chromium.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@gmail.com>
> Fixes: f05ed4d56e9c ("KVM: PPC: Split out code from book3s.c into book3s_pr.c")
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed-by: Nick Desaulniers <ndesaulniers@google.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