[src/trunk]: src/sys/uvm Reported-by: syzbot+3e3c7cfa8093f8de047e@syzkaller.a...

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

details:   https://anonhg.NetBSD.org/src/rev/6136ab66f221
branches:  trunk
changeset: 932787:6136ab66f221
user:      ad <ad%NetBSD.org@localhost>
date:      Fri May 15 22:35:05 2020 +0000

description:
Reported-by: syzbot+3e3c7cfa8093f8de047e%syzkaller.appspotmail.com@localhost

Comment out an assertion that's now bogus and add a comment.

diffstat:

 sys/uvm/uvm_fault.c |  10 +++++++---
 1 files changed, 7 insertions(+), 3 deletions(-)

diffs (33 lines):

diff -r a28b1eda13fb -r 6136ab66f221 sys/uvm/uvm_fault.c
--- a/sys/uvm/uvm_fault.c       Fri May 15 22:27:04 2020 +0000
+++ b/sys/uvm/uvm_fault.c       Fri May 15 22:35:05 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_fault.c,v 1.225 2020/04/13 22:22:19 ad Exp $       */
+/*     $NetBSD: uvm_fault.c,v 1.226 2020/05/15 22:35:05 ad Exp $       */
 
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -32,7 +32,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_fault.c,v 1.225 2020/04/13 22:22:19 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_fault.c,v 1.226 2020/05/15 22:35:05 ad Exp $");
 
 #include "opt_uvmhist.h"
 
@@ -1701,9 +1701,13 @@
                 * but rather that the pmap should be designed such that it
                 * never needs to fail when the new mapping is replacing an
                 * existing mapping and the new page has no existing mappings.
+                *
+                * XXX This can't be asserted safely any more because many
+                * LWPs and/or many processes could simultaneously fault on
+                * the same VA and some might succeed.
                 */
 
-               KASSERT(!pmap_extract(pmap, va, NULL));
+               /* KASSERT(!pmap_extract(pmap, va, NULL)); */
 
                /*
                 * ensure that the page is queued in the case that