From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarkko Sakkinen Subject: Re: [PATCH v17 18/23] platform/x86: Intel SGX driver Date: Tue, 18 Dec 2018 15:13:11 +0200 Message-ID: <20181218131311.GB25667@linux.intel.com> References: <20181116010412.23967-1-jarkko.sakkinen@linux.intel.com> <20181116010412.23967-19-jarkko.sakkinen@linux.intel.com> <7d5cde02-4649-546b-0f03-2d6414bb80b5@intel.com> <20181217180102.GA12560@linux.intel.com> <20181217183613.GD12491@linux.intel.com> <20181217184333.GA26920@linux.intel.com> <20181217184858.GF12491@linux.intel.com> <20181217193322.GA29785@linux.intel.com> <20181217202149.GA19053@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20181217202149.GA19053@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org To: Sean Christopherson Cc: Dave Hansen , x86@kernel.org, platform-driver-x86@vger.kernel.org, linux-sgx@vger.kernel.org, nhorman@redhat.com, npmccallum@redhat.com, serge.ayoun@intel.com, shay.katz-zamir@intel.com, haitao.huang@linux.intel.com, andriy.shevchenko@linux.intel.com, tglx@linutronix.de, kai.svahn@intel.com, mark.shanahan@intel.com, luto@amacapital.net, Suresh Siddha , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Darren Hart , Andy Shevchenko , "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" List-Id: platform-driver-x86.vger.kernel.org On Mon, Dec 17, 2018 at 10:21:49PM +0200, Jarkko Sakkinen wrote: > On Mon, Dec 17, 2018 at 09:33:22PM +0200, Jarkko Sakkinen wrote: > > On Mon, Dec 17, 2018 at 10:48:58AM -0800, Sean Christopherson wrote: > > > On Mon, Dec 17, 2018 at 08:43:33PM +0200, Jarkko Sakkinen wrote: > > > > On Mon, Dec 17, 2018 at 10:36:13AM -0800, Sean Christopherson wrote: > > > > > I'm pretty sure doing mmget() would result in circular dependencies and > > > > > a zombie enclave. In the do_exit() case where a task is abruptly killed: > > > > > > > > > > - __mmput() is never called because the enclave holds a ref > > > > > - sgx_encl_release() is never be called because its VMAs hold refs > > > > > - sgx_vma_close() is never called because __mmput()->exit_mmap() is > > > > > blocked and the process itself is dead, i.e. won't unmap anything. > > > > > > > > Right, it does, you are absolutely right. Tried it and removed the > > > > commit already. > > > > > > > > Well, what we came up from your suggestion i.e. setting mm to NULL > > > > and checking that is very subtle change and does not have any such > > > > circular dependencies. We'll go with that. > > > > > > We can't set mm to NULL as we need it to unregister the notifier, and > > > I'm fairly certain attempting to unregister in the release callback > > > will deadlock. > > > > Noticed that too. mmu_notifier_unregister() requires a valid mm. > > Both branches updated... I'm not still seeing why you would want to call sgx_free_page() from sgx_invalidate(). Kind of resistant to adding extra logging just for checking for programming errors. What I would do if I had to debug there a leak would be simply put kretprobe on __sgx_free_page(). /Jarkko