linux-hardening - Re: [PATCH] ARM: vexpress/spc: Avoid negative array index when !SMP

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Message-ID: <YkbFvYRkcXgo3mpK@e110455-lin.cambridge.arm.com>
Date:   Fri, 1 Apr 2022 10:28:29 +0100
From:   Liviu Dudau <liviu.dudau@....com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Russell King <linux@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] ARM: vexpress/spc: Avoid negative array index when !SMP

On Thu, Mar 31, 2022 at 12:04:43PM -0700, Kees Cook wrote:
> When building multi_v7_defconfig+CONFIG_SMP=n, -Warray-bounds exposes
> a couple negative array index accesses:
> 
> arch/arm/mach-vexpress/spc.c: In function 've_spc_clk_init':
> arch/arm/mach-vexpress/spc.c:583:21: warning: array subscript -1 is below array bounds of 'bool[2]' {aka '_Bool[2]'} [-Warray-bounds]
>   583 |   if (init_opp_table[cluster])
>       |       ~~~~~~~~~~~~~~^~~~~~~~~
> arch/arm/mach-vexpress/spc.c:556:7: note: while referencing 'init_opp_table'
>   556 |  bool init_opp_table[MAX_CLUSTERS] = { false };
>       |       ^~~~~~~~~~~~~~
> arch/arm/mach-vexpress/spc.c:592:18: warning: array subscript -1 is below array bounds of 'bool[2]' {aka '_Bool[2]'} [-Warray-bounds]
>   592 |    init_opp_table[cluster] = true;
>       |    ~~~~~~~~~~~~~~^~~~~~~~~
> arch/arm/mach-vexpress/spc.c:556:7: note: while referencing 'init_opp_table'
>   556 |  bool init_opp_table[MAX_CLUSTERS] = { false };
>       |       ^~~~~~~~~~~~~~
> 
> Skip this logic when built !SMP.
> 
> Cc: Liviu Dudau <liviu.dudau@....com>
> Cc: Sudeep Holla <sudeep.holla@....com>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> Cc: Russell King <linux@...linux.org.uk>
> Cc: linux-arm-kernel@...ts.infradead.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

Acked-by: Liviu Dudau <liviu.dudau@....com>

Sudeep, can you please take this through your tree for sending it to arm-soc?

Best regards,
Liviu

> ---
>  arch/arm/mach-vexpress/spc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mach-vexpress/spc.c b/arch/arm/mach-vexpress/spc.c
> index 1da11bdb1dfb..1c6500c4e6a1 100644
> --- a/arch/arm/mach-vexpress/spc.c
> +++ b/arch/arm/mach-vexpress/spc.c
> @@ -580,7 +580,7 @@ static int __init ve_spc_clk_init(void)
>  		}
> 
>  		cluster = topology_physical_package_id(cpu_dev->id);
> -		if (init_opp_table[cluster])
> +		if (cluster < 0 || init_opp_table[cluster])
>  			continue;
> 
>  		if (ve_init_opp_table(cpu_dev))
> --
> 2.32.0
> 

-- 
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