From c28f922c9dcee0e4876a2c095939d77fe7e15116 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 1 Jun 2025 20:11:06 -0400 Subject: [PATCH] clone_private_mnt(): make sure that caller has CAP_SYS_ADMIN in the right userns What we want is to verify there is that clone won't expose something hidden by a mount we wouldn't be able to undo. "Wouldn't be able to undo" may be a result of MNT_LOCKED on a child, but it may also come from lacking admin rights in the userns of the namespace mount belongs to. clone_private_mnt() checks the former, but not the latter. There's a number of rather confusing CAP_SYS_ADMIN checks in various userns during the mount, especially with the new mount API; they serve different purposes and in case of clone_private_mnt() they usually, but not always end up covering the missing check mentioned above. Reviewed-by: Christian Brauner Reported-by: "Orlando, Noah" Fixes: 427215d85e8d ("ovl: prevent private clone if bind mount is not allowed") Signed-off-by: Al Viro --- fs/namespace.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/namespace.c b/fs/namespace.c index 2e939b783618..1c54c16c7bab 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2510,6 +2510,9 @@ struct vfsmount *clone_private_mount(const struct path *path) return ERR_PTR(-EINVAL); } + if (!ns_capable(old_mnt->mnt_ns->user_ns, CAP_SYS_ADMIN)) + return ERR_PTR(-EPERM); + if (__has_locked_children(old_mnt, path->dentry)) return ERR_PTR(-EINVAL); -- 2.25.1