From c686ee4685c227c730fdb2467b400b7a793fbc1a Mon Sep 17 00:00:00 2001
From: Konstantin Belousov <kib@FreeBSD.org>
Date: Mon, 1 Apr 2013 09:59:38 +0000
Subject: [PATCH] Do not call the VOP_LOOKUP() for the doomed directory vnode. 
 The vnode could be reclaimed while lock upgrade was performed.

Sponsored by:	The FreeBSD Foundation
Reported and tested by:	pho
Diagnosed and reviewed by:	rmacklem
MFC after:	1 week
---
 sys/kern/vfs_lookup.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c
index 94d11f291b5..cf7323110bd 100644
--- a/sys/kern/vfs_lookup.c
+++ b/sys/kern/vfs_lookup.c
@@ -698,6 +698,10 @@ unionlookup:
 	    VOP_ISLOCKED(dp) == LK_SHARED &&
 	    (cnp->cn_flags & ISLASTCN) && (cnp->cn_flags & LOCKPARENT))
 		vn_lock(dp, LK_UPGRADE|LK_RETRY);
+	if ((dp->v_iflag & VI_DOOMED) != 0) {
+		error = ENOENT;
+		goto bad;
+	}
 	/*
 	 * If we're looking up the last component and we need an exclusive
 	 * lock, adjust our lkflags.