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
..
compat.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
ipc_sysctl.c	ipc/msg: increase MSGMNI, remove scaling	2014-12-13 12:42:52 -08:00
Makefile	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
mq_sysctl.c	ipc: convert use of typedef ctl_table to struct ctl_table	2014-06-06 16:08:16 -07:00
mqueue.c	Revert "mqueue: switch to on-demand creation of internal mount"	2018-03-24 19:34:23 -05:00
msg.c	ipc: fix ipc data structures inconsistency	2018-02-06 18:32:46 -08:00
msgutil.c	ipc: convert ipc_namespace.count from atomic_t to refcount_t	2017-09-08 18:26:51 -07:00
namespace.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
sem.c	ipc: fix ipc data structures inconsistency	2018-02-06 18:32:46 -08:00
shm.c	ipc: fix ipc data structures inconsistency	2018-02-06 18:32:46 -08:00
syscall.c	Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2017-11-17 12:54:01 -08:00
util.c	ipc: fix ipc data structures inconsistency	2018-02-06 18:32:46 -08:00
util.h	sysvipc: make get_maxid O(1) again	2017-11-17 16:10:04 -08:00