6.15-stable review patch. If anyone has any objections, please let me know.
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From: Al Viro viro@zeniv.linux.org.uk
[ Upstream commit c28f922c9dcee0e4876a2c095939d77fe7e15116 ]
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 brauner@kernel.org Reported-by: "Orlando, Noah" Noah.Orlando@deshaw.com Fixes: 427215d85e8d ("ovl: prevent private clone if bind mount is not allowed") Signed-off-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Sasha Levin sashal@kernel.org --- fs/namespace.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/fs/namespace.c b/fs/namespace.c index 07bc500a248ec..163ffdc042284 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2509,6 +2509,9 @@ 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);