linux-kernel - [PATCHv2 0/3] fs: add O_BENEATH flag to openat(2)

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Date:	Tue,  4 Nov 2014 09:54:41 +0000
From:	David Drysdale <drysdale@...gle.com>
To:	linux-kernel@...r.kernel.org,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Kees Cook <keescook@...omium.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Meredydd Luff <meredydd@...atehouse.org>,
	Will Drewry <wad@...omium.org>,
	Jorge Lucangeli Obes <jorgelo@...gle.com>,
	Ricky Zhou <rickyz@...gle.com>,
	Lee Campbell <leecam@...gle.com>,
	Julien Tinnes <jln@...gle.com>,
	Mike Depinet <mdepinet@...gle.com>,
	James Morris <james.l.morris@...cle.com>,
	Andy Lutomirski <luto@...capital.net>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Paul Moore <paul@...l-moore.com>,
	Christoph Hellwig <hch@...radead.org>,
	linux-api@...r.kernel.org, linux-security-module@...r.kernel.org,
	David Drysdale <drysdale@...gle.com>
Subject: [PATCHv2 0/3] fs: add O_BENEATH flag to openat(2)

This change adds a new O_BENEATH flag for openat(2) which restricts the
provided path, rejecting (with -EACCES) paths that are not beneath
the provided dfd.

This change was previously included as part of a larger patchset
(https://lkml.org/lkml/2014/7/25/426) for Capsicum support; however, it
is potentially useful as an independent change so I've pulled it out
separately here.

In particular, various folks from Chrome[OS] have indicated an interest
in having this functionality -- when combined with a seccomp filter it
allows a directory to be accessed by a sandboxed process.


Changes since v1:
 - Don't needlessly duplicate flags [Al Viro]
 - Use EPERM rather than EACCES as error code [Paolo Bonzini]
 - Disallow nd_jump_link for O_BENEATH [Al Viro/Andy Lutomirski]
 - Add test of a jumped symlink (/proc/self/root)

Changes since the version included in the Capsicum v2 patchset:
 - Add tests of normal symlinks
 - Fix man-page typo
 - Update patch to 3.17

Changes from v1 to v2 of Capsicum patchset:
 - renamed O_BENEATH_ONLY to O_BENEATH [Christoph Hellwig]


David Drysdale (2):
  fs: add O_BENEATH flag to openat(2)
  selftests: Add test of O_BENEATH & openat(2)

 arch/alpha/include/uapi/asm/fcntl.h       |   1 +
 arch/parisc/include/uapi/asm/fcntl.h      |   1 +
 arch/sparc/include/uapi/asm/fcntl.h       |   1 +
 fs/fcntl.c                                |   5 +-
 fs/namei.c                                |  43 ++++++---
 fs/open.c                                 |   4 +-
 include/linux/namei.h                     |   1 +
 include/uapi/asm-generic/fcntl.h          |   4 +
 tools/testing/selftests/Makefile          |   1 +
 tools/testing/selftests/openat/.gitignore |   3 +
 tools/testing/selftests/openat/Makefile   |  24 +++++
 tools/testing/selftests/openat/openat.c   | 149 ++++++++++++++++++++++++++++++
 12 files changed, 220 insertions(+), 17 deletions(-)
 create mode 100644 tools/testing/selftests/openat/.gitignore
 create mode 100644 tools/testing/selftests/openat/Makefile
 create mode 100644 tools/testing/selftests/openat/openat.c

--
2.1.0.rc2.206.gedb03e5

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