Eric W. Biederman 5aac93adff userns: Don't fail follow_automount based on s_user_ns
[ Upstream commit bbc3e47101 ]

When vfs_submount was added the test to limit automounts from
filesystems that with s_user_ns != &init_user_ns accidentially left
in follow_automount.  The test was never about any security concerns
and was always about how do we implement this for filesystems whose
s_user_ns != &init_user_ns.

At the moment this check makes no difference as there are no
filesystems that both set FS_USERNS_MOUNT and implement d_automount.

Remove this check now while I am thinking about it so there will not
be odd booby traps for someone who does want to make this combination
work.

vfs_submount still needs improvements to allow this combination to work,
and vfs_submount contains a check that presents a warning.

The autofs4 filesystem could be modified to set FS_USERNS_MOUNT and it would
need not work on this code path, as userspace performs the mounts.

Fixes: 93faccbbfa ("fs: Better permission checking for submounts")
Fixes: aeaa4a79ff ("fs: Call d_automount with the filesystems creds")
Acked-by:  Ian Kent <raven@themaw.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-03-19 08:42:50 +01:00
…
2018-03-15 10:54:38 +01:00

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.
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