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Date:   Tue, 15 Nov 2022 13:00:40 -0800
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Subject: Re: [PATCH v3 36/37] x86/cet/shstk: Add ARCH_CET_UNLOCK
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To:     Peter Zijlstra <peterz@infradead.org>,
        "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
Cc:     "bsingharora@gmail.com" <bsingharora@gmail.com>,
        "hpa@zytor.com" <hpa@zytor.com>,
        "Syromiatnikov, Eugene" <esyr@redhat.com>,
        "rdunlap@infradead.org" <rdunlap@infradead.org>,
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        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
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        "Eranian, Stephane" <eranian@google.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "fweimer@redhat.com" <fweimer@redhat.com>,
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        "Yang, Weijiang" <weijiang.yang@intel.com>,
        "Lutomirski, Andy" <luto@kernel.org>,
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References: <20221104223604.29615-1-rick.p.edgecombe@intel.com>
 <20221104223604.29615-37-rick.p.edgecombe@intel.com>
 <Y3OmaSjhCtjht1nS@hirez.programming.kicks-ass.net>
 <4273232513cd178be303d817b15e442703bda637.camel@intel.com>
 <Y3P9V1c0ytuC2/3g@hirez.programming.kicks-ass.net>
From:   Dave Hansen <dave.hansen@intel.com>
In-Reply-To: <Y3P9V1c0ytuC2/3g@hirez.programming.kicks-ass.net>
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On 11/15/22 12:57, Peter Zijlstra wrote:
> On Tue, Nov 15, 2022 at 08:01:12PM +0000, Edgecombe, Rick P wrote:
>>>> +	if (task != current) {
>>>> +		if (option == ARCH_CET_UNLOCK &&
>>>> IS_ENABLED(CONFIG_CHECKPOINT_RESTORE)) {
>>> Why make this conditional on CRIU at all?
>> Kees asked for it, I think he was worried about attackers using it to
>> unlock and disable shadow stack. So wanted to lock it down to the
>> maximum.
> Well, distros will all have this stuff enabled no? So not much
> protection in practise.

Yeah, that's true for the distros.

But, I would imagine that our more paranoid friends like the ChromeOS
folks might appreciate this.