linux-kernel - Re: [PATCH 1/4][RFC v2] PM / sleep: Avoid accessing frozen

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Date:	Sat, 25 Jun 2016 18:51:13 +0200
From:	Pavel Machek <pavel@....cz>
To:	Chen Yu <yu.c.chen@...el.com>
Cc:	linux-pm@...r.kernel.org, x86@...nel.org,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <lenb@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...e.de>,
	Brian Gerst <brgerst@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Varun Koyyalagunta <cpudebug@...ttech.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4][RFC v2] PM / sleep: Avoid accessing frozen_cpus if
 it is NULL

On Sun 2016-06-26 00:18:30, Chen Yu wrote:
> frozen_cpus might be NULL if the allocation in previous
> alloc_frozen_cpus failed, when CONFIG_CPUMASK_OFFSTACK
> is set.
> 
> This patch avoid accessing this cpumask if it is NULL.
> 
> Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> ---
>  kernel/cpu.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index d948e44..d25266e 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -1021,6 +1021,8 @@ int disable_nonboot_cpus(void)
>  {
>  	int cpu, first_cpu, error = 0;
>  
> +	if (frozen_cpus == NULL)
> +		return -ENOMEM;
>  	cpu_maps_update_begin();
>  	first_cpu = cpumask_first(cpu_online_mask);
>  	/*

I'd say that whoever allocates frozen_cpus should just abort the
hibernation if there's not enough memory for the operation...? This
seems like checking for the problem too late.

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html