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Tue, 22 Sep 2020 15:11:21 +0000 (UTC) IronPort-SDR: 8xKPTgmhjXx7HFbdcat7NHkIrBdnaC1afAEX58XBXD86/JJYB2dh/mZ1SKibn8bTiXP+B5KvGE PoCp6lkVkoUA== X-IronPort-AV: E=McAfee;i="6000,8403,9752"; a="224770641" X-IronPort-AV: E=Sophos;i="5.77,291,1596524400"; d="scan'208";a="224770641" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2020 08:11:18 -0700 IronPort-SDR: r0vsBNNWp+RiNqr9S4/k3cQeFzh5SLwbw9DWKnoVJuFhXb6Gy1TnwAo9N7YLGKbo/YAzah7kUE 7hNbMs6U5pRw== X-IronPort-AV: E=Sophos;i="5.77,291,1596524400"; d="scan'208";a="309528660" Received: from subratmo-mobl.amr.corp.intel.com (HELO [10.209.179.63]) ([10.209.179.63]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2020 08:11:15 -0700 Subject: Re: [PATCH v38 10/24] mm: Add vm_ops->mprotect() To: Jarkko Sakkinen , Andy Lutomirski Cc: Sean Christopherson , Andy Lutomirski , X86 ML , linux-sgx@vger.kernel.org, LKML , Linux-MM , Andrew Morton , Matthew Wilcox , Jethro Beekman , Darren Kenny , Andy Shevchenko , asapek@google.com, Borislav Petkov , "Xing, Cedric" , chenalexchen@google.com, Conrad Parker , cyhanish@google.com, "Huang, Haitao" , Josh Triplett , "Huang, Kai" , "Svahn, Kai" , Keith Moyer , Christian Ludloff , Neil Horman , Nathaniel McCallum , Patrick Uiterwijk , David Rientjes , Thomas Gleixner , yaozhangx@google.com References: <20200918235337.GA21189@sjchrist-ice> <1B23E216-0229-4BDD-8B09-807256A54AF5@amacapital.net> <20200922125801.GA133710@linux.intel.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200922125801.GA133710@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable 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 9/22/20 5:58 AM, Jarkko Sakkinen wrote: > Intel Sofware Guard eXtensions (SGX) allows creation of executable blob= s > called enclaves, of which page permissions are defined when the enclave "of which" =3D> "for which" > is first loaded. Once an enclave is loaded and initialized, it can be > mapped to the process address space. Could you compare and contrast this a *bit* with existing executables? What's special about SGX? ELF executables have page permissions inside the binary too. Why don't we use this mechanism for them? > Enclave permissions can be dynamically modified by using ENCLS[EMODPE] I'm not sure this sentence matters. I'm not sure why I care what the instruction is named that does this. But, it _sounds_ here like an enclave can adjust its own permissions directly with ENCLS[EMODPE]. > instruction. We want to limit its use to not allow higher permissions t= han > the ones defined when the enclave was first created. Rather than higher and lower, please use stronger and weaker. Also, please get rid of the "we". > Add 'mprotect' hook to vm_ops, so that we can implement a callback for = SGX > that will check that {mmap, mprotect}() permissions do not surpass any = of > the page permissions in the address range defined. "check" =3D> "ensure" > This is required in order to be able to make any access control decisio= ns > when enclave pages are loaded. Now I'm confused. I actually don't think I have a strong understanding of how an enclave actually gets loaded, how mmap() and mprotect() are normally used and what this hook is intended to thwart.