31f71f2d7a
commit 46f5ab762d048dad224436978315cbc2fa79c630 upstream. When we added mount_setattr() I added additional checks compared to the legacy do_reconfigure_mnt() and do_change_type() helpers used by regular mount(2). If that mount had a parent then verify that the caller and the mount namespace the mount is attached to match and if not make sure that it's an anonymous mount. The real rootfs falls into neither category. It is neither an anoymous mount because it is obviously attached to the initial mount namespace but it also obviously doesn't have a parent mount. So that means legacy mount(2) allows changing mount properties on the real rootfs but mount_setattr(2) blocks this. I never thought much about this but of course someone on this planet of earth changes properties on the real rootfs as can be seen in [1]. Since util-linux finally switched to the new mount api in 2.39 not so long ago it also relies on mount_setattr() and that surfaced this issue when Fedora 39 finally switched to it. Fix this. Link: https://bugzilla.redhat.com/show_bug.cgi?id=2256843 Link: https://lore.kernel.org/r/20240206-vfs-mount-rootfs-v1-1-19b335eee133@kernel.org Reviewed-by: Jan Kara <jack@suse.cz> Reported-by: Karel Zak <kzak@redhat.com> Cc: stable@vger.kernel.org # v5.12+ Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.