linux-kernel - Re: [Patch v3 12/13] x86/speculation: Protect non-dumpable processes against Spectre v2 attack

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Message-ID: <alpine.DEB.2.21.1810181713330.3566@nanos.tec.linutronix.de>
Date:   Thu, 18 Oct 2018 17:17:29 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
cc:     Jiri Kosina <jikos@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Casey Schaufler <casey.schaufler@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Jon Masters <jcm@...hat.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org
Subject: Re: [Patch v3 12/13] x86/speculation: Protect non-dumpable processes
 against Spectre v2 attack

On Wed, 17 Oct 2018, Tim Chen wrote:
> +void arch_set_dumpable(struct task_struct *tsk, unsigned int value)
> +{
> +	bool update;
> +
> +	if (!static_branch_unlikely(&spectre_v2_app_lite))
> +		return;
> +	if (!static_cpu_has(X86_FEATURE_STIBP))
> +		return;
> +	if (spectre_v2_app2app_enabled == SPECTRE_V2_APP2APP_NONE)
> +		return;

Can spectre_v2_app_lite be enabled when the cpu does not support STIBP or
spectre_v2_app2app_enabled is not set to SPECTRE_V2_APP2APP_CMD_LITE?

No it cannot. So checking the static key is sufficient.

Thanks,

	tglx