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Eric W. Biederman cfb2f6f6e0 Revert "mqueue: switch to on-demand creation of internal mount" 
This reverts commit 36735a6a2b.

Aleksa Sarai <asarai@suse.de> writes:
> [REGRESSION v4.16-rc6] [PATCH] mqueue: forbid unprivileged user access to internal mount
>
> Felix reported weird behaviour on 4.16.0-rc6 with regards to mqueue[1],
> which was introduced by 36735a6a2b ("mqueue: switch to on-demand
> creation of internal mount").
>
> Basically, the reproducer boils down to being able to mount mqueue if
> you create a new user namespace, even if you don't unshare the IPC
> namespace.
>
> Previously this was not possible, and you would get an -EPERM. The mount
> is the *host* mqueue mount, which is being cached and just returned from
> mqueue_mount(). To be honest, I'm not sure if this is safe or not (or if
> it was intentional -- since I'm not familiar with mqueue).
>
> To me it looks like there is a missing permission check. I've included a
> patch below that I've compile-tested, and should block the above case.
> Can someone please tell me if I'm missing something? Is this actually
> safe?
>
> [1]: https://github.com/docker/docker/issues/36674

The issue is a lot deeper than a missing permission check.  sb->s_user_ns
was is improperly set as well.  So in addition to the filesystem being
mounted when it should not be mounted, so things are not allow that should
be.

We are practically to the release of 4.16 and there is no agreement between
Al Viro and myself on what the code should looks like to fix things properly.
So revert the code to what it was before so that we can take our time
and discuss this properly.

Fixes: 36735a6a2b ("mqueue: switch to on-demand creation of internal mount")
Reported-by: Felix Abecassis <fabecassis@nvidia.com>
Reported-by: Aleksa Sarai <asarai@suse.de>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-03-24 19:34:23 -05:00
arch Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-02-18 12:56:41 -08:00
block blk: optimization for classic polling 2018-02-13 09:12:04 -07:00
certs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2018-02-12 08:57:21 -08:00
Documentation ACPI updates for v4.16-rc2 2018-02-15 14:50:32 -08:00
drivers Merge branch 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-02-18 12:22:04 -08:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs for-4.16-rc1-tag 2018-02-16 09:26:18 -08:00
include Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-02-18 11:54:22 -08:00
init membarrier: Provide core serializing command, *_SYNC_CORE 2018-02-05 21:35:03 +01:00
ipc Revert "mqueue: switch to on-demand creation of internal mount" 2018-03-24 19:34:23 -05:00
kernel Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-02-18 12:38:40 -08:00
lib dma-direct: comment the dma_direct_free calling convention 2018-02-12 15:59:07 +00:00
LICENSES LICENSES: Add MPL-1.1 license 2018-01-06 10:59:44 -07:00
mm mm: hide a #warning for COMPILE_TEST 2018-02-16 09:41:36 -08:00
net virtio: bugfixes 2018-02-15 14:29:27 -08:00
samples sample/bpf: fix erspan metadata 2018-02-06 11:32:49 -05:00
scripts Kbuild updates for v4.16 (2nd) 2018-02-09 19:32:41 -08:00
security vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
sound ALSA: hda/realtek: PCI quirk for Fujitsu U7x7 2018-02-14 12:02:26 +01:00
tools perf/core improvements and fixes: 2018-02-16 09:10:09 +01:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore scripts/package: snap-pkg target 2017-12-13 00:00:18 +09:00
.mailmap mailmap: update Mark Yao's email address 2018-01-04 16:45:09 -08:00
COPYING
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-02-14 17:02:15 -08:00
Makefile Linux 4.16-rc2 2018-02-18 17:29:42 -08:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

README 

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.