[src/trunk]: src/sys/uvm in uvm_mapent_forkzero(), if the old entry was an ob...

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

details:   https://anonhg.NetBSD.org/src/rev/040fce28cac5
branches:  trunk
changeset: 380021:040fce28cac5
user:      chs <chs%NetBSD.org@localhost>
date:      Thu Jul 01 15:06:01 2021 +0000

description:
in uvm_mapent_forkzero(), if the old entry was an object mapping,
appease a debug check by setting the new entry offset to zero along with
setting the new entry object pointer to NULL.

Reported-by: syzbot+de8e4b223a3838c7307b%syzkaller.appspotmail.com@localhost
Reported-by: syzbot+efaea991addfdcc5abd4%syzkaller.appspotmail.com@localhost
Reported-by: syzbot+15d1e19dff9209c2e40b%syzkaller.appspotmail.com@localhost

diffstat:

 sys/uvm/uvm_map.c |  5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diffs (26 lines):

diff -r 14ed7279b1c4 -r 040fce28cac5 sys/uvm/uvm_map.c
--- a/sys/uvm/uvm_map.c Thu Jul 01 04:25:51 2021 +0000
+++ b/sys/uvm/uvm_map.c Thu Jul 01 15:06:01 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_map.c,v 1.389 2021/06/20 07:11:38 mrg Exp $        */
+/*     $NetBSD: uvm_map.c,v 1.390 2021/07/01 15:06:01 chs Exp $        */
 
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -66,7 +66,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_map.c,v 1.389 2021/06/20 07:11:38 mrg Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_map.c,v 1.390 2021/07/01 15:06:01 chs Exp $");
 
 #include "opt_ddb.h"
 #include "opt_pax.h"
@@ -4451,6 +4451,7 @@ uvm_mapent_forkzero(struct vm_map *new_m
                        new_entry->object.uvm_obj->pgops->pgo_detach(
                            new_entry->object.uvm_obj);
                new_entry->object.uvm_obj = NULL;
+               new_entry->offset = 0;
                new_entry->etype &= ~UVM_ET_OBJ;
        }
 }