Re: [PATCH] fs: don't allow non-init s_user_ns for filesystems without FS_USERNS_MOUNT

[Christian Brauner]

On Wed, 24 Jul 2024 09:53:59 -0500, Seth Forshee (DigitalOcean) wrote:
> Christian noticed that it is possible for a privileged user to mount
> most filesystems with a non-initial user namespace in sb->s_user_ns.
> When fsopen() is called in a non-init namespace the caller's namespace
> is recorded in fs_context->user_ns. If the returned file descriptor is
> then passed to a process priviliged in init_user_ns, that process can
> call fsconfig(fd_fs, FSCONFIG_CMD_CREATE), creating a new superblock
> with sb->s_user_ns set to the namespace of the process which called
> fsopen().
> 
> [...]

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: don't allow non-init s_user_ns for filesystems without FS_USERNS_MOUNT
      https://git.kernel.org/vfs/vfs/c/f7c589ccd630