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15 Nov 2022 13:00:42 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10532"; a="813821204" X-IronPort-AV: E=Sophos;i="5.96,166,1665471600"; d="scan'208";a="813821204" Received: from dn-intelpc-071822.amr.corp.intel.com (HELO [10.212.229.216]) ([10.212.229.216]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Nov 2022 13:00:40 -0800 Message-ID: <93029063-4a68-d275-b437-12930e119347@intel.com> Date: Tue, 15 Nov 2022 13:00:40 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Subject: Re: [PATCH v3 36/37] x86/cet/shstk: Add ARCH_CET_UNLOCK Content-Language: en-US To: Peter Zijlstra , "Edgecombe, Rick P" Cc: "bsingharora@gmail.com" , "hpa@zytor.com" , "Syromiatnikov, Eugene" , "rdunlap@infradead.org" , "keescook@chromium.org" , "dave.hansen@linux.intel.com" , "kirill.shutemov@linux.intel.com" , "Eranian, Stephane" , "linux-mm@kvack.org" , "fweimer@redhat.com" , "nadav.amit@gmail.com" , "jannh@google.com" , "dethoma@microsoft.com" , "rppt@linux.ibm.com" , "linux-arch@vger.kernel.org" , "kcc@google.com" , "bp@alien8.de" , "oleg@redhat.com" , "hjl.tools@gmail.com" , "Yang, Weijiang" , "Lutomirski, Andy" , "pavel@ucw.cz" , "arnd@arndb.de" , "tglx@linutronix.de" , "mike.kravetz@oracle.com" , "x86@kernel.org" , "linux-doc@vger.kernel.org" , "jamorris@linux.microsoft.com" , "rppt@kernel.org" , "john.allen@amd.com" , "mingo@redhat.com" , "Shankar, Ravi V" , "corbet@lwn.net" , "linux-kernel@vger.kernel.org" , "linux-api@vger.kernel.org" , "gorcunov@gmail.com" , "akpm@linux-foundation.org" References: <20221104223604.29615-1-rick.p.edgecombe@intel.com> <20221104223604.29615-37-rick.p.edgecombe@intel.com> <4273232513cd178be303d817b15e442703bda637.camel@intel.com> From: Dave Hansen In-Reply-To: Content-Type: text/plain; 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bh=fq8RRIvTKXZsRg31SQ63baSiLhxGFic57KWy3pKhd8c=; b=Z5OZhL6hN17c6sV9H98uoa5gVlQEWMPqTJordfrHFZe2mPsRz+jCJWPoTtkv3gzwfaggvi jYhZxIR20x1s2lnEZ//zUnW4+BvjjzBpugcNTTs8My/y4Wdt35j+l3c3LpmyQEqAwfoJDX zBTAt2R+mFFt8/kMvsCKXMCpnRUKPsM= X-Stat-Signature: 3wz5ge616wunh7d4m3dk3z1ns43bs57e X-Rspamd-Queue-Id: 80CE1A0010 Authentication-Results: imf15.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b=N3DEQZ+d; spf=pass (imf15.hostedemail.com: domain of dave.hansen@intel.com designates 192.55.52.120 as permitted sender) smtp.mailfrom=dave.hansen@intel.com; dmarc=pass (policy=none) header.from=intel.com X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1668546048-49532 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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.