[src/trunk]: src/sys/kern Make namei() work with no root dir yet.

[hannken <hannken%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/b596c2cc3373
branches:  trunk
changeset: 842649:b596c2cc3373
user:      hannken <hannken%NetBSD.org@localhost>
date:      Thu Jul 18 09:39:40 2019 +0000

description:
Make namei() work with no root dir yet.

>From David Holland with minor tweaks from me.

Should fix PR kern/54378 (panic with TLB miss when attempting to reboot)

diffstat:

 sys/kern/vfs_lookup.c |  23 +++++++++++++++++------
 1 files changed, 17 insertions(+), 6 deletions(-)

diffs (72 lines):

diff -r dd1810cd45fa -r b596c2cc3373 sys/kern/vfs_lookup.c
--- a/sys/kern/vfs_lookup.c     Thu Jul 18 09:07:59 2019 +0000
+++ b/sys/kern/vfs_lookup.c     Thu Jul 18 09:39:40 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vfs_lookup.c,v 1.211 2019/07/06 14:27:38 maxv Exp $    */
+/*     $NetBSD: vfs_lookup.c,v 1.212 2019/07/18 09:39:40 hannken Exp $ */
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1993
@@ -37,7 +37,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_lookup.c,v 1.211 2019/07/06 14:27:38 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_lookup.c,v 1.212 2019/07/18 09:39:40 hannken Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_magiclinks.h"
@@ -515,7 +515,8 @@
        KASSERT(state->cnp == &state->ndp->ni_cnd);
 
        if (state->root_referenced) {
-               vrele(state->ndp->ni_rootdir);
+               if (state->ndp->ni_rootdir != NULL)
+                       vrele(state->ndp->ni_rootdir);
                if (state->ndp->ni_erootdir != NULL)
                        vrele(state->ndp->ni_erootdir);
        }
@@ -538,7 +539,8 @@
        struct vnode *rootdir, *erootdir, *curdir, *startdir;
 
        if (state->root_referenced) {
-               vrele(state->ndp->ni_rootdir);
+               if (state->ndp->ni_rootdir != NULL)
+                       vrele(state->ndp->ni_rootdir);
                if (state->ndp->ni_erootdir != NULL)
                        vrele(state->ndp->ni_erootdir);
                state->root_referenced = 0;
@@ -595,8 +597,10 @@
         * Must hold references to rootdir and erootdir while we're running.
         * A multithreaded process may chroot during namei.
         */
-       vref(startdir);
-       vref(state->ndp->ni_rootdir);
+       if (startdir != NULL)
+               vref(startdir);
+       if (state->ndp->ni_rootdir != NULL)
+               vref(state->ndp->ni_rootdir);
        if (state->ndp->ni_erootdir != NULL)
                vref(state->ndp->ni_erootdir);
        state->root_referenced = 1;
@@ -616,6 +620,9 @@
        KASSERT(state->ndp->ni_atdir != NULL);
 
        /* always use the real root, and never set an emulation root */
+       if (rootvnode == NULL) {
+               return NULL;
+       }
        state->ndp->ni_rootdir = rootvnode;
        state->ndp->ni_erootdir = NULL;
 
@@ -693,6 +700,10 @@
                namei_ktrace(state);
        }
 
+       if (startdir == NULL) {
+               return ENOENT;
+       }
+
        /* NDAT may feed us with a non directory namei_getstartdir */
        if (startdir->v_type != VDIR) {
                vrele(startdir);