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This reverts commit36735a6a2b. 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 by36735a6a2b("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>
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.