Re: kern/54378 (panic with TLB miss when attempting to reboot)

["J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>]

The following reply was made to PR kern/54378; it has been noted by GNATS.

From: "J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: dholland%NetBSD.org@localhost
Subject: Re: kern/54378 (panic with TLB miss when attempting to reboot)
Date: Wed, 17 Jul 2019 12:20:14 +0200

 On Tue, Jul 16, 2019 at 02:42:56PM +0000, dholland%NetBSD.org@localhost wrote:
 > I suspect the recent rootdir refcount changes in namei; could you take a
 > quick look? If not, please set it to me...
 
 No, we have "rootvnode == NULL", call namei() for "/mnt/netbsd" and
 come to namei_getstartdir().  Here we have "startdir == rootvnode == NULL",
 try to reference with vref(startdir) and bomb.
 
 This patch should fix it, please give it a try.
 
 --
 J. Hannken-Illjes - hannken%eis.cs.tu-bs.de@localhost - TU Braunschweig
 
 diff -r be1f0ec66ecd sys/kern/vfs_lookup.c
 --- sys/kern/vfs_lookup.c	Wed Jul 17 10:51:07 2019 +0200
 +++ sys/kern/vfs_lookup.c	Wed Jul 17 11:36:42 2019 +0200
 @@ -1563,6 +1563,9 @@ namei(struct nameidata *ndp)
  	struct namei_state state;
  	int error;
  
 +	if (rootvnode == NULL)
 +		return ENOENT;
 +
  	namei_init(&state, ndp);
  	error = namei_tryemulroot(&state,
  				  0/*!neverfollow*/, 0/*!inhibitmagic*/,
 @@ -1597,6 +1600,9 @@ lookup_for_nfsd(struct nameidata *ndp, s
  	struct namei_state state;
  	int error;
  
 +	if (rootvnode == NULL)
 +		return ENOENT;
 +
  	KASSERT(ndp->ni_atdir == NULL);
  	ndp->ni_atdir = forcecwd;