From 0d9e99ce3b1071c76ff5a2d9d4158341c0371c2f Mon Sep 17 00:00:00 2001
From: Mateusz Guzik <mjg@FreeBSD.org>
Date: Sat, 18 Sep 2021 10:12:27 +0200
Subject: [PATCH] vfs: add the missing vnode interlock in vfs_mountroot_shuffle

Around v_mountedhere assignment.
---
 sys/kern/vfs_mountroot.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sys/kern/vfs_mountroot.c b/sys/kern/vfs_mountroot.c
index e2a687511e11..5cf222901420 100644
--- a/sys/kern/vfs_mountroot.c
+++ b/sys/kern/vfs_mountroot.c
@@ -367,10 +367,12 @@ vfs_mountroot_shuffle(struct thread *td, struct mount *mpdevfs)
 				error = vinvalbuf(vp, V_SAVE, 0, 0);
 			if (!error) {
 				cache_purge(vp);
+				VI_LOCK(vp);
 				mporoot->mnt_vnodecovered = vp;
 				vp->v_mountedhere = mporoot;
 				strlcpy(mporoot->mnt_stat.f_mntonname,
 				    fspath, MNAMELEN);
+				VI_UNLOCK(vp);
 				VOP_UNLOCK(vp);
 			} else
 				vput(vp);