linux-kernel - Re: [PATCH] irqchip/gic: prevent buffer overflow in gic_ipi_send

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Message-ID: <87cyli5zj7.ffs@tglx>
Date: Thu, 05 Sep 2024 09:29:32 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Sergey Shtylyov <s.shtylyov@....ru>, linux-kernel@...r.kernel.org, Marc
 Zyngier <maz@...nel.org>, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] irqchip/gic: prevent buffer overflow in
 gic_ipi_send_mask()

On Wed, Sep 04 2024 at 23:23, Sergey Shtylyov wrote:
> ARM GIC arch v2 spec claims support for just 8 CPU interfaces.  However,
> looking at the GIC driver's irq_set_affinity() method, it seems that the
> passed CPU mask may contain the logical CPU #s beyond 8, and that method
> filters them out before reading gic_cpu_map[], bailing out with
> -EINVAL.

The reasoning is correct in theory, but in reality it's a non problem.

Simply because processors which use this GIC version cannot have more
than 8 cores.

That means num_possible_cpus() <= 8 so the cpumask handed in cannot have
bits >= 8 set. Ergo for_each_cpu() can't return a bit which is >= 8.

Thanks

        tglx