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From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Thu, 8 Jun 2023 10:09:53 +0200
Message-ID: <CAMj1kXFErhC7k+zg2ga-Lgo9f6muarbO6AJVx3g0KCGTLWkakg@mail.gmail.com>
Subject: Re: [PATCH][next] ARM: OMAP2+: Fix -Warray-bounds warning in _pwrdm_state_switch()
To:     "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc:     Tony Lindgren <tony@atomide.com>,
        Russell King <linux@armlinux.org.uk>,
        "Peter 'p2' De Schrijver" <peter.de-schrijver@nokia.com>,
        Kevin Hilman <khilman@deeprootsystems.com>,
        linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
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On Thu, 8 Jun 2023 at 06:11, Gustavo A. R. Silva <gustavoars@kernel.org> wrote:
>
> If function pwrdm_read_prev_pwrst() returns -EINVAL, we will end
> up accessing array pwrdm->state_counter through negative index
> -22. This is wrong and the compiler is legitimately warning us
> about this potential problem.
>
> Fix this by sanity checking the value stored in variable _prev_
> before accessing array pwrdm->state_counter.
>
> Address the following -Warray-bounds warning:
> arch/arm/mach-omap2/powerdomain.c:178:45: warning: array subscript -22 is below array bounds of 'unsigned int[4]' [-Warray-bounds]
>
> Link: https://github.com/KSPP/linux/issues/307
> Fixes: ba20bb126940 ("OMAP: PM counter infrastructure.")
> Cc: stable@vger.kernel.org
> Reported-by: kernel test robot <lkp@intel.com>
> Link: https://lore.kernel.org/lkml/20230607050639.LzbPn%25lkp@intel.com/
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Nice to see this work paying off.

Acked-by: Ard Biesheuvel <ardb@kernel.org>

Does the error case need further handling here?


> ---
>  arch/arm/mach-omap2/powerdomain.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/mach-omap2/powerdomain.c b/arch/arm/mach-omap2/powerdomain.c
> index 777f9f8e7cd8..5e05dd1324e7 100644
> --- a/arch/arm/mach-omap2/powerdomain.c
> +++ b/arch/arm/mach-omap2/powerdomain.c
> @@ -174,7 +174,7 @@ static int _pwrdm_state_switch(struct powerdomain *pwrdm, int flag)
>                 break;
>         case PWRDM_STATE_PREV:
>                 prev = pwrdm_read_prev_pwrst(pwrdm);
> -               if (pwrdm->state != prev)
> +               if (prev >= 0 && pwrdm->state != prev)
>                         pwrdm->state_counter[prev]++;
>                 if (prev == PWRDM_POWER_RET)
>                         _update_logic_membank_counters(pwrdm);
> --
> 2.34.1
>
>
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