linux-kernel - Re: [PATCH] ARM: STi: at least warn if of

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Date:   Mon, 16 Jul 2018 07:55:08 +0000
From:   Patrice CHOTARD <patrice.chotard@...com>
To:     Nicholas Mc Guire <hofrat@...dl.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...com>
CC:     Russell King <linux@...linux.org.uk>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: STi: at least warn if of_iomap fails

Hi Nicholas

On 07/12/2018 05:48 PM, Nicholas Mc Guire wrote:
> The call to of_iomap() is unchecked but scu_enable(), which the returned
> address is passed on to, assumes a valid mapping. If the mapping is
> invalid this could probably lead to undefined system state so at least
> a warning should be issued.
> 
> Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
> Fixes: commit 65ebcc115889 ("ARM: sti: Add STiH415 SOC support")
> ---
> Problem was found by an experimental coccinelle script
> 
> Patch was compile tested with: multi_v7_defconfig (implies
> CONFIG_ARCH_STI=y, CONFIG_SMP=y)
> 
> Patch is against 4.18-rc3 (localversion-next is next-20180712)
> 
>   arch/arm/mach-sti/platsmp.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm/mach-sti/platsmp.c b/arch/arm/mach-sti/platsmp.c
> index 231f19e..89ae76f 100644
> --- a/arch/arm/mach-sti/platsmp.c
> +++ b/arch/arm/mach-sti/platsmp.c
> @@ -109,6 +109,7 @@ static void __init sti_smp_prepare_cpus(unsigned int max_cpus)
>   
>   	if (np) {
>   		scu_base = of_iomap(np, 0);
> +		WARN_ON(!scu_base);
>   		scu_enable(scu_base);
>   		of_node_put(np);
>   	}
> 

I should prefer to exit with an error to avoid unpredictable behavior,
something like this is better :

scu_base = of_iomap(np, 0);
of_node_put(np);
if (!scu_base) {
	pr_err("No SCU remap\n");
	return;
}

scu_enable(scu_base);


Thanks