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Subject: Re: [RFC PATCH 2/9] x86/sgx: Do not naturally align MAP_FIXED address
From:   Andy Lutomirski <luto@amacapital.net>
In-Reply-To: <20190605151653.GK11331@linux.intel.com>
Date:   Wed, 5 Jun 2019 13:14:04 -0700
Cc:     "Xing, Cedric" <cedric.xing@intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        "Christopherson, Sean J" <sean.j.christopherson@intel.com>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        James Morris <jmorris@namei.org>,
        "Serge E . Hallyn" <serge@hallyn.com>,
        LSM List <linux-security-module@vger.kernel.org>,
        Paul Moore <paul@paul-moore.com>,
        Eric Paris <eparis@parisplace.org>,
        "selinux@vger.kernel.org" <selinux@vger.kernel.org>,
        Jethro Beekman <jethro@fortanix.com>,
        "Hansen, Dave" <dave.hansen@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
        "linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        "nhorman@redhat.com" <nhorman@redhat.com>,
        "npmccallum@redhat.com" <npmccallum@redhat.com>,
        "Ayoun, Serge" <serge.ayoun@intel.com>,
        "Katz-zamir, Shay" <shay.katz-zamir@intel.com>,
        "Huang, Haitao" <haitao.huang@intel.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        "Svahn, Kai" <kai.svahn@intel.com>, Borislav Petkov <bp@alien8.de>,
        Josh Triplett <josh@joshtriplett.org>,
        "Huang, Kai" <kai.huang@intel.com>,
        David Rientjes <rientjes@google.com>,
        "Roberts, William C" <william.c.roberts@intel.com>,
        "Tricca, Philip B" <philip.b.tricca@intel.com>
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References: <20190531233159.30992-1-sean.j.christopherson@intel.com> <20190531233159.30992-3-sean.j.christopherson@intel.com> <20190604114951.GC30594@linux.intel.com> <CALCETrVe0jhAWAFmx+NFEjJcijSJv2LDVC7cUXi0w99kNKjh_g@mail.gmail.com> <960B34DE67B9E140824F1DCDEC400C0F654EDBDE@ORSMSX116.amr.corp.intel.com> <20190605151653.GK11331@linux.intel.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Sender: linux-kernel-owner@vger.kernel.org
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> On Jun 5, 2019, at 8:17 AM, Jarkko Sakkinen <jarkko.sakkinen@linux.intel.c=
om> wrote:
>=20
>> On Tue, Jun 04, 2019 at 10:10:22PM +0000, Xing, Cedric wrote:
>> A bit off topic here. This mmap()/mprotect() discussion reminds me a
>> question (guess for Jarkko): Now that vma->vm_file->private_data keeps
>> a pointer to the enclave, why do we store it again in vma->vm_private?
>> It isn't a big deal but non-NULL vm_private does prevent mprotect()
>> from merging adjacent VMAs.=20
>=20
> Same semantics as with a regular mmap i.e. you can close the file and
> still use the mapping.
>=20
>=20

The file should be properly refcounted =E2=80=94 vm_file should not go away w=
hile it=E2=80=99s mapped.=