From patchwork Thu Jun 6 02:11:43 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 10978315 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 183B63A3F for ; Thu, 6 Jun 2019 02:12:05 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0A800200E5 for ; Thu, 6 Jun 2019 02:12:05 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id F261828710; Thu, 6 Jun 2019 02:12:04 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9D4C2200E5 for ; Thu, 6 Jun 2019 02:12:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726743AbfFFCLw (ORCPT ); Wed, 5 Jun 2019 22:11:52 -0400 Received: from mga17.intel.com ([192.55.52.151]:61633 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726724AbfFFCLv (ORCPT ); Wed, 5 Jun 2019 22:11:51 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Jun 2019 19:11:50 -0700 X-ExtLoop1: 1 Received: from sjchrist-coffee.jf.intel.com ([10.54.74.36]) by orsmga004.jf.intel.com with ESMTP; 05 Jun 2019 19:11:49 -0700 From: Sean Christopherson To: Jarkko Sakkinen Cc: Andy Lutomirski , Cedric Xing , Stephen Smalley , James Morris , "Serge E . Hallyn" , LSM List , Paul Moore , Eric Paris , selinux@vger.kernel.org, Jethro Beekman , Dave Hansen , Thomas Gleixner , Linus Torvalds , LKML , X86 ML , linux-sgx@vger.kernel.org, Andrew Morton , nhorman@redhat.com, npmccallum@redhat.com, Serge Ayoun , Shay Katz-zamir , Haitao Huang , Andy Shevchenko , Kai Svahn , Borislav Petkov , Josh Triplett , Kai Huang , David Rientjes , William Roberts , Philip Tricca Subject: [RFC PATCH v2 3/5] x86/sgx: Enforce noexec filesystem restriction for enclaves Date: Wed, 5 Jun 2019 19:11:43 -0700 Message-Id: <20190606021145.12604-4-sean.j.christopherson@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190606021145.12604-1-sean.j.christopherson@intel.com> References: <20190606021145.12604-1-sean.j.christopherson@intel.com> MIME-Version: 1.0 Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP Do not allow an enclave page to be mapped with PROT_EXEC if the source vma does not have VM_MAYEXEC. This effectively enforces noexec as do_mmap() clears VM_MAYEXEC if the vma is being loaded from a noexec path, i.e. prevents executing a file by loading it into an enclave. Checking noexec indirectly by way of VM_MAYEXEC naturally handles any other cases that clear VM_MAYEXEC to deny execute permissions. Signed-off-by: Sean Christopherson --- arch/x86/kernel/cpu/sgx/driver/ioctl.c | 47 +++++++++++++++++++++++--- 1 file changed, 42 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/cpu/sgx/driver/ioctl.c b/arch/x86/kernel/cpu/sgx/driver/ioctl.c index ef5c2ce0f37b..44b2d73de7c3 100644 --- a/arch/x86/kernel/cpu/sgx/driver/ioctl.c +++ b/arch/x86/kernel/cpu/sgx/driver/ioctl.c @@ -577,6 +577,44 @@ static int sgx_encl_add_page(struct sgx_encl *encl, unsigned long addr, return ret; } +static int sgx_encl_page_copy(void *dst, unsigned long src, unsigned long prot) +{ + struct vm_area_struct *vma; + int ret; + + if (!(prot & VM_EXEC)) + return 0; + + /* Hold mmap_sem across copy_from_user() to avoid a TOCTOU race. */ + down_read(¤t->mm->mmap_sem); + + vma = find_vma(current->mm, src); + if (!vma) { + ret = -EFAULT; + goto out; + } + + /* + * Query VM_MAYEXEC as an indirect path_noexec() check (see do_mmap()), + * but with some future proofing against other cases that may deny + * execute permissions. + */ + if (!(vma->vm_flags & VM_MAYEXEC)) { + ret = -EACCES; + goto out; + } + + if (copy_from_user(dst, (void __user *)src, PAGE_SIZE)) + ret = -EFAULT; + else + ret = 0; + +out: + up_read(¤t->mm->mmap_sem); + + return ret; +} + /** * sgx_ioc_enclave_add_page - handler for %SGX_IOC_ENCLAVE_ADD_PAGE * @@ -616,13 +654,12 @@ static long sgx_ioc_enclave_add_page(struct file *filep, unsigned int cmd, data = kmap(data_page); - if (copy_from_user((void *)data, (void __user *)addp->src, PAGE_SIZE)) { - ret = -EFAULT; - goto out; - } - prot = addp->flags & (PROT_READ | PROT_WRITE | PROT_EXEC); + ret = sgx_encl_page_copy(data, addp->src, prot); + if (ret) + goto out; + ret = sgx_encl_add_page(encl, addp->addr, data, &secinfo, addp->mrmask, prot); if (ret)