Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751810AbaFENkp (ORCPT ); Thu, 5 Jun 2014 09:40:45 -0400 Received: from mail-wi0-f201.google.com ([209.85.212.201]:62245 "EHLO mail-wi0-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751407AbaFENkm (ORCPT ); Thu, 5 Jun 2014 09:40:42 -0400 From: David Drysdale To: Alexander Viro , Meredydd Luff , linux-kernel@vger.kernel.org Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Andrew Morton , Kees Cook , Arnd Bergmann , x86@kernel.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, David Drysdale Subject: [PATCHv4 RESEND 0/3] syscalls,x86: Add execveat() system call Date: Thu, 5 Jun 2014 14:40:32 +0100 Message-Id: <1401975635-6162-1-git-send-email-drysdale@google.com> X-Mailer: git-send-email 2.0.0.526.g5318336 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Resending, adding cc:linux-api. Also, it may help to add a little more background -- this patch is needed as a (small) part of implementing Capsicum in the Linux kernel. Capsicum is a security framework that has been present in FreeBSD since version 9.0 (Jan 2012), and is based on concepts from object-capability security [1]. One of the features of Capsicum is capability mode, which locks down access to global namespaces such as the filesystem hierarchy. In capability mode, /proc is thus inaccessible and so fexecve(3) doesn't work -- hence the need for a kernel-space alternative. [1] http://www.cl.cam.ac.uk/research/security/capsicum/papers/2010usenix-security-capsicum-website.pdf ------ This patch set adds execveat(2) for x86, and is derived from Meredydd Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528). The primary aim of adding an execveat syscall is to allow an implementation of fexecve(3) that does not rely on the /proc filesystem. The current glibc version of fexecve(3) is implemented via /proc, which causes problems in sandboxed or otherwise restricted environments. Given the desire for a /proc-free fexecve() implementation, HPA suggested (https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be an appropriate generalization. Also, having a new syscall means that it can take a flags argument without back-compatibility concerns. The current implementation just defines the AT_SYMLINK_NOFOLLOW flag, but other flags could be added in future -- for example, flags for new namespaces (as suggested at https://lkml.org/lkml/2006/7/11/474). Related history: - https://lkml.org/lkml/2006/12/27/123 is an example of someone realizing that fexecve() is likely to fail in a chroot environment. - http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered documenting the /proc requirement of fexecve(3) in its manpage, to "prevent other people from wasting their time". - https://bugzilla.kernel.org/show_bug.cgi?id=74481 documented that it's not possible to fexecve() a file descriptor for a script with close-on-exec set (which is possible with the implementation here). - https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a problem where a process that did setuid() could not fexecve() because it no longer had access to /proc/self/fd; this has since been fixed. Changes since Meredydd's v3 patch: - Added a selftest. - Added a man page. - Left open_exec() signature untouched to reduce patch impact elsewhere (as suggested by Al Viro). - Filled in bprm->filename with d_path() into a buffer, to avoid use of potentially-ephemeral dentry->d_name. - Patch against v3.14 (455c6fdbd21916). David Drysdale (2): syscalls,x86: implement execveat() system call syscalls,x86: add selftest for execveat(2) arch/x86/ia32/audit.c | 1 + arch/x86/ia32/ia32entry.S | 1 + arch/x86/kernel/audit_64.c | 1 + arch/x86/kernel/entry_64.S | 28 ++++ arch/x86/syscalls/syscall_32.tbl | 1 + arch/x86/syscalls/syscall_64.tbl | 2 + arch/x86/um/sys_call_table_64.c | 1 + fs/exec.c | 153 ++++++++++++++++--- include/linux/compat.h | 3 + include/linux/sched.h | 4 + include/linux/syscalls.h | 4 + include/uapi/asm-generic/unistd.h | 4 +- kernel/sys_ni.c | 3 + lib/audit.c | 3 + tools/testing/selftests/Makefile | 1 + tools/testing/selftests/exec/.gitignore | 6 + tools/testing/selftests/exec/Makefile | 32 ++++ tools/testing/selftests/exec/execveat.c | 251 ++++++++++++++++++++++++++++++++ 18 files changed, 476 insertions(+), 23 deletions(-) create mode 100644 tools/testing/selftests/exec/.gitignore create mode 100644 tools/testing/selftests/exec/Makefile create mode 100644 tools/testing/selftests/exec/execveat.c -- 1.9.1.423.g4596e3a -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/