5.15-stable review patch. If anyone has any objections, please let me know.
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From: Al Viro viro@zeniv.linux.org.uk
commit c28f922c9dcee0e4876a2c095939d77fe7e15116 upstream.
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 [ merge conflict resolution: clone_private_mount() was reworked in db04662e2f4f ("fs: allow detached mounts in clone_private_mount()"). Tweak the relevant ns_capable check so that it works on older kernels ] Signed-off-by: Noah Orlando Noah.Orlando@deshaw.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/namespace.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/fs/namespace.c +++ b/fs/namespace.c @@ -1975,6 +1975,11 @@ struct vfsmount *clone_private_mount(con if (!check_mnt(old_mnt)) goto invalid;
+ if (!ns_capable(old_mnt->mnt_ns->user_ns, CAP_SYS_ADMIN)) { + up_read(&namespace_sem); + return ERR_PTR(-EPERM); + } + if (has_locked_children(old_mnt, path->dentry)) goto invalid;