From patchwork Thu Mar 18 19:43:01 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dave Hansen X-Patchwork-Id: 12149133 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 30B07C433E6 for ; Thu, 18 Mar 2021 19:45:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 08A2E64F04 for ; Thu, 18 Mar 2021 19:45:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229958AbhCRTpC (ORCPT ); Thu, 18 Mar 2021 15:45:02 -0400 Received: from mga14.intel.com ([192.55.52.115]:43786 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231552AbhCRTos (ORCPT ); Thu, 18 Mar 2021 15:44:48 -0400 IronPort-SDR: gS7s3daWyOHjR1UsUzQCq+ezpWKB/laO6qG0tvEDJeIb/l+vYAFhwgHGHCTKxP1uVv6P5Zyj0v DxLPl2BVq5Mw== X-IronPort-AV: E=McAfee;i="6000,8403,9927"; a="189133751" X-IronPort-AV: E=Sophos;i="5.81,259,1610438400"; d="scan'208";a="189133751" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Mar 2021 12:44:48 -0700 IronPort-SDR: KZJvqpBBX9snehXC78xGJ5MeQ/cu4J2F9D95rSp5nXtelJoVcOJhbaQcoGJSykTojDpzSvSc5B FUASbeNpbk9A== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.81,259,1610438400"; d="scan'208";a="406495840" Received: from viggo.jf.intel.com (HELO localhost.localdomain) ([10.54.77.144]) by fmsmga008.fm.intel.com with ESMTP; 18 Mar 2021 12:44:47 -0700 Subject: [PATCH] selftests/sgx: improve error detection and messages To: linux-kernel@vger.kernel.org Cc: Dave Hansen , jarkko@kernel.org, shuah@kernel.org, bp@alien8.de, x86@kernel.org, linux-sgx@vger.kernel.org, linux-kselftest@vger.kernel.org From: Dave Hansen Date: Thu, 18 Mar 2021 12:43:01 -0700 Message-Id: <20210318194301.11D9A984@viggo.jf.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org From: Dave Hansen The SGX device file (/dev/sgx_enclave) is unusual in that it requires execute permissions. It has to be both "chmod +x" *and* be on a filesystem without 'noexec'. In the future, udev and systemd should get updates to set up systems automatically. But, for now, nobody's systems do this automatically, and everybody gets error messages like this when running ./test_sgx: 0x0000000000000000 0x0000000000002000 0x03 0x0000000000002000 0x0000000000001000 0x05 0x0000000000003000 0x0000000000003000 0x03 mmap() failed, errno=1. That isn't very user friendly, even for forgetful kernel developers. Further, the test case is rather haphazard about its use of fprintf() versus perror(). Improve the error messages. Use perror() where possible. Lastly, do some sanity checks on opening and mmap()ing the device file so that we can get a decent error message out to the user. Now, if your user doesn't have permission, you'll get the following: $ ls -l /dev/sgx_enclave crw------- 1 root root 10, 126 Mar 18 11:29 /dev/sgx_enclave $ ./test_sgx Unable to open /dev/sgx_enclave: Permission denied If you then 'chown dave:dave /dev/sgx_enclave' (or whatever), but you leave execute permissions off, you'll get: $ ls -l /dev/sgx_enclave crw------- 1 dave dave 10, 126 Mar 18 11:29 /dev/sgx_enclave $ ./test_sgx no execute permissions on device file If you fix that with "chmod ug+x /dev/sgx" but you leave /dev as noexec, you'll get this: $ mount | grep "/dev .*noexec" udev on /dev type devtmpfs (rw,nosuid,noexec,...) $ ./test_sgx ERROR: mmap for exec: Operation not permitted mmap() succeeded for PROT_READ, but failed for PROT_EXEC check that user has execute permissions on /dev/sgx_enclave and that /dev does not have noexec set: 'mount | grep "/dev .*noexec"' That can be fixed with: mount -o remount,noexec /devESC Hopefully, the combination of better error messages and the search engines indexing this message will help people fix their systems until we do this properly. Signed-off-by: Dave Hansen Cc: Jarkko Sakkinen Cc: Shuah Khan Cc: Borislav Petkov Cc: x86@kernel.org Cc: linux-sgx@vger.kernel.org Cc: linux-kselftest@vger.kernel.org Reviewed-by: Jarkko Sakkinen --- b/tools/testing/selftests/sgx/load.c | 66 +++++++++++++++++++++++++++-------- b/tools/testing/selftests/sgx/main.c | 2 - 2 files changed, 53 insertions(+), 15 deletions(-) diff -puN tools/testing/selftests/sgx/load.c~sgx-selftest-err-rework tools/testing/selftests/sgx/load.c --- a/tools/testing/selftests/sgx/load.c~sgx-selftest-err-rework 2021-03-18 12:18:38.649828215 -0700 +++ b/tools/testing/selftests/sgx/load.c 2021-03-18 12:40:46.388824904 -0700 @@ -45,19 +45,19 @@ static bool encl_map_bin(const char *pat fd = open(path, O_RDONLY); if (fd == -1) { - perror("open()"); + perror("enclave executable open()"); return false; } ret = stat(path, &sb); if (ret) { - perror("stat()"); + perror("enclave executable stat()"); goto err; } bin = mmap(NULL, sb.st_size, PROT_READ, MAP_PRIVATE, fd, 0); if (bin == MAP_FAILED) { - perror("mmap()"); + perror("enclave executable mmap()"); goto err; } @@ -90,8 +90,7 @@ static bool encl_ioc_create(struct encl ioc.src = (unsigned long)secs; rc = ioctl(encl->fd, SGX_IOC_ENCLAVE_CREATE, &ioc); if (rc) { - fprintf(stderr, "SGX_IOC_ENCLAVE_CREATE failed: errno=%d\n", - errno); + perror("SGX_IOC_ENCLAVE_CREATE failed"); munmap((void *)secs->base, encl->encl_size); return false; } @@ -116,31 +115,69 @@ static bool encl_ioc_add_pages(struct en rc = ioctl(encl->fd, SGX_IOC_ENCLAVE_ADD_PAGES, &ioc); if (rc < 0) { - fprintf(stderr, "SGX_IOC_ENCLAVE_ADD_PAGES failed: errno=%d.\n", - errno); + perror("SGX_IOC_ENCLAVE_ADD_PAGES failed"); return false; } return true; } + + bool encl_load(const char *path, struct encl *encl) { + const char device_path[] = "/dev/sgx_enclave"; Elf64_Phdr *phdr_tbl; off_t src_offset; Elf64_Ehdr *ehdr; + struct stat sb; + void *ptr; int i, j; int ret; + int fd = -1; memset(encl, 0, sizeof(*encl)); - ret = open("/dev/sgx_enclave", O_RDWR); - if (ret < 0) { - fprintf(stderr, "Unable to open /dev/sgx_enclave\n"); + fd = open(device_path, O_RDWR); + if (fd < 0) { + perror("Unable to open /dev/sgx_enclave"); + goto err; + } + + ret = stat(device_path, &sb); + if (ret) { + perror("device file stat()"); + goto err; + } + + /* + * This just checks if the /dev file has these permission + * bits set. It does not check that the current user is + * the owner or in the owning group. + */ + if (!(sb.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))) { + fprintf(stderr, "no execute permissions on device file\n"); + goto err; + } + + ptr = mmap(NULL, PAGE_SIZE, PROT_READ, MAP_SHARED, fd, 0); + if (ptr == (void *)-1) { + perror("mmap for read"); + goto err; + } + munmap(ptr, PAGE_SIZE); + + ptr = mmap(NULL, PAGE_SIZE, PROT_EXEC, MAP_SHARED, fd, 0); + if (ptr == (void *)-1) { + perror("ERROR: mmap for exec"); + fprintf(stderr, "mmap() succeeded for PROT_READ, but failed for PROT_EXEC\n"); + fprintf(stderr, "check that user has execute permissions on %s and\n", device_path); + fprintf(stderr, "that /dev does not have noexec set: 'mount | grep \"/dev .*noexec\"'\n"); goto err; } + munmap(ptr, PAGE_SIZE); - encl->fd = ret; + encl->fd = fd; if (!encl_map_bin(path, encl)) goto err; @@ -217,6 +254,8 @@ bool encl_load(const char *path, struct return true; err: + if (fd != -1) + close(fd); encl_delete(encl); return false; } @@ -229,7 +268,7 @@ static bool encl_map_area(struct encl *e area = mmap(NULL, encl_size * 2, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (area == MAP_FAILED) { - perror("mmap"); + perror("reservation mmap()"); return false; } @@ -268,8 +307,7 @@ bool encl_build(struct encl *encl) ioc.sigstruct = (uint64_t)&encl->sigstruct; ret = ioctl(encl->fd, SGX_IOC_ENCLAVE_INIT, &ioc); if (ret) { - fprintf(stderr, "SGX_IOC_ENCLAVE_INIT failed: errno=%d\n", - errno); + perror("SGX_IOC_ENCLAVE_INIT failed"); return false; } diff -puN tools/testing/selftests/sgx/main.c~sgx-selftest-err-rework tools/testing/selftests/sgx/main.c --- a/tools/testing/selftests/sgx/main.c~sgx-selftest-err-rework 2021-03-18 12:18:38.652828215 -0700 +++ b/tools/testing/selftests/sgx/main.c 2021-03-18 12:18:38.657828215 -0700 @@ -195,7 +195,7 @@ int main(int argc, char *argv[], char *e addr = mmap((void *)encl.encl_base + seg->offset, seg->size, seg->prot, MAP_SHARED | MAP_FIXED, encl.fd, 0); if (addr == MAP_FAILED) { - fprintf(stderr, "mmap() failed, errno=%d.\n", errno); + perror("mmap() segment failed"); exit(KSFT_FAIL); } }