6.15-stable review patch. If anyone has any objections, please let me know.
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From: KONDO KAZUMA(近藤 和真) kazuma-kondo@nec.com
[ Upstream commit 4954346d80fb047cb78776d9f2ebd6a050f80c5f ]
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].
Reviewed-by: Christian Brauner brauner@kernel.org 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@zeniv.linux.org.uk Signed-off-by: Kazuma Kondo kazuma-kondo@nec.com Signed-off-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Sasha Levin sashal@kernel.org --- fs/namespace.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c index e2780f413a2e0..07bc500a248ec 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2492,18 +2492,19 @@ struct vfsmount *clone_private_mount(const struct path *path) if (IS_MNT_UNBINDABLE(old_mnt)) return ERR_PTR(-EINVAL);
- if (mnt_has_parent(old_mnt)) { - if (!check_mnt(old_mnt)) - return ERR_PTR(-EINVAL); - } else { - if (!is_mounted(&old_mnt->mnt)) - return ERR_PTR(-EINVAL); - - /* Make sure this isn't something purely kernel internal. */ - if (!is_anon_ns(old_mnt->mnt_ns)) + /* + * Make sure the source mount is acceptable. + * Anything mounted in our mount namespace is allowed. + * Otherwise, it must be the root of an anonymous mount + * namespace, and we need to make sure no namespace + * loops get created. + */ + if (!check_mnt(old_mnt)) { + if (!is_mounted(&old_mnt->mnt) || + !is_anon_ns(old_mnt->mnt_ns) || + mnt_has_parent(old_mnt)) return ERR_PTR(-EINVAL);
- /* Make sure we don't create mount namespace loops. */ if (!check_for_nsfs_mounts(old_mnt)) return ERR_PTR(-EINVAL); }