linux-kernel - Re: [PATCH 3/3] genirq/irqdomain: Detect type race in irq_create_fwspec

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Message-ID: <e86441c4-9ce2-b0f2-f8ca-2823497b4d6d@kernel.org>
Date:   Fri, 20 Sep 2019 17:07:26 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     "Sverdlin, Alexander (Nokia - DE/Ulm)" <alexander.sverdlin@...ia.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Grant Likely <grant.likely@...retlab.ca>
Cc:     Mark Brown <broonie@...nsource.wolfsonmicro.com>,
        Jon Hunter <jonathanh@...dia.com>,
        "Glavinic-Pecotic, Matija (EXT - DE/Ulm)" 
        <matija.glavinic-pecotic.ext@...ia.com>,
        "Adamski, Krzysztof (Nokia - PL/Wroclaw)" 
        <krzysztof.adamski@...ia.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH 3/3] genirq/irqdomain: Detect type race in
 irq_create_fwspec_mapping()

On 12/09/2019 10:44, Sverdlin, Alexander (Nokia - DE/Ulm) wrote:
> From: Alexander Sverdlin <alexander.sverdlin@...ia.com>
> 
> irq_create_fwspec_mapping() can race with itself during IRQ trigger type
> configuration. Possible scenarios include:
> 
> - Mapping exists, two irq_create_fwspec_mapping() running in parallel do
>   not detect type mismatch, IRQ remains configured with one of the
>   different trigger types randomly
> - Second call to irq_create_fwspec_mapping() sees existing mapping just
>   created by first call, but earlier irqd_set_trigger_type() call races
>   with later irqd_set_trigger_type() => totally undetected, IRQ type
>   is being set randomly to either one or another type

Is that an actual thing? Frankly, the scenario you're describing here
seems to carry the hallmarks of a completely broken system. Can you
point at a system supported in mainline that would behave as such?

Thanks,

	M.
-- 
Jazz is not dead, it just smells funny...