On Wed, Jun 04, 2025 at 12:20:11AM +0100, Al Viro wrote:
> From: =?UTF-8?q?KONDO=20KAZUMA=28=E8=BF=91=E8=97=A4=E3=80=80=E5=92=8C?=
> =?UTF-8?q?=E7=9C=9F=29?= <kazuma-kondo@xxxxxxx>
>
> Mounting overlayfs with a directory on real rootfs (initramfs)
> as upperdir has failed with following message since commit
> db04662e2f4f ("fs: allow detached mounts in clone_private_mount()").
>
> [ 4.080134] overlayfs: failed to clone upperpath
>
> Overlayfs mount uses clone_private_mount() to create internal mount
> for the underlying layers.
>
> The commit made clone_private_mount() reject real rootfs because
> it does not have a parent mount and is in the initial mount namespace,
> that is not an anonymous mount namespace.
>
> This issue can be fixed by modifying the permission check
> of clone_private_mount() following [1].
>
> Fixes: db04662e2f4f ("fs: allow detached mounts in clone_private_mount()")
> Link: https://lore.kernel.org/all/20250514190252.GQ2023217@ZenIV/ [1]
> Link: https://lore.kernel.org/all/20250506194849.GT2023217@ZenIV/
> Suggested-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Kazuma Kondo <kazuma-kondo@xxxxxxx>
> Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> ---
Reviewed-by: Christian Brauner <brauner@xxxxxxxxxx>
