On Tue, 06 Feb 2024 11:22:09 +0100, Christian Brauner wrote: > 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]. > > [...] Applied to the vfs.fixes branch of the vfs/vfs.git tree. Patches in the vfs.fixes branch should appear in linux-next soon. Please report any outstanding bugs that were missed during review in a new review to the original patch series allowing us to drop it. It's encouraged to provide Acked-bys and Reviewed-bys even though the patch has now been applied. If possible patch trailers will be updated. Note that commit hashes shown below are subject to change due to rebase, trailer updates or similar. If in doubt, please check the listed branch. tree: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git branch: vfs.fixes [1/1] fs: relax mount_setattr() permission checks https://git.kernel.org/vfs/vfs/c/853c4204729e
