Re: [syzbot] Re: [syzbot] [overlayfs?] general protection fault in clone_private_mount

[syzbot <syzbot+62dfea789a2cedac1298@syzkaller.appspotmail.com>]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: Re: [syzbot] [overlayfs?] general protection fault in clone_private_mount
Author: lizhi.xu@windriver.com

#syz test

diff --git a/fs/namespace.c b/fs/namespace.c
index 1314f11ed961..8e2ff3dbab58 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2421,6 +2421,9 @@ struct vfsmount *clone_private_mount(const struct path *path)
 		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))
 			return ERR_PTR(-EINVAL);