NetBSD Problem Report #56965
From www@netbsd.org Thu Aug 11 12:33:19 2022
Return-Path: <www@netbsd.org>
Received: from mail.netbsd.org (mail.netbsd.org [199.233.217.200])
(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits))
(Client CN "mail.NetBSD.org", Issuer "mail.NetBSD.org CA" (not verified))
by mollari.NetBSD.org (Postfix) with ESMTPS id 575951A921F
for <gnats-bugs@gnats.NetBSD.org>; Thu, 11 Aug 2022 12:33:19 +0000 (UTC)
Message-Id: <20220811123317.8C73E1A9239@mollari.NetBSD.org>
Date: Thu, 11 Aug 2022 12:33:17 +0000 (UTC)
From: campbell+netbsd@mumble.net
Reply-To: campbell+netbsd@mumble.net
To: gnats-bugs@NetBSD.org
Subject: panic messages are sometimes garbled in syzkaller
X-Send-Pr-Version: www-1.0
>Number: 56965
>Category: kern
>Synopsis: panic messages are sometimes garbled in syzkaller
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: kern-bug-people
>State: open
>Class: sw-bug
>Submitter-Id: net
>Arrival-Date: Thu Aug 11 12:35:01 +0000 2022
>Originator: Taylor R Campbell
>Release: current
>Organization:
La Fondation NètBSD
>Environment:
not sure
>Description:
Panic messages are sometimes garbled in syzkaller reports, such as this one:
[ 388.47pmap58845] panic: _get_physpage: out of memory
https://syzkaller.appspot.com/bug?id=5458c4ca59f15645a6a7a035a3399b7b1cb18714
Somehow part of the message `pmap_get_physpage: out of memory' has appeared in the middle of the dmesg timestamp, and _before_ the text `panic: ', even though the logic in subr_prf.c is serialized by a mutex and prints `panic: ' first:
265 kprintf_lock();
266 kprintf_internal("panic: ", TOLOG|TOCONS, NULL, NULL);
267 if (panicstr == NULL) {
268 /* first time in panic - store fmt first for precaution */
269 panicstr = fmt;
270
271 vsnprintf(scratchstr, sizeof(scratchstr), fmt, ap);
272 kprintf_internal("%s", TOLOG|TOCONS, NULL, NULL, scratchstr);
273 panicstr = scratchstr;
274 } else {
275 kprintf(fmt, TOLOG|TOCONS, NULL, NULL, ap);
276 }
277 kprintf_internal("\n", TOLOG|TOCONS, NULL, NULL);
278 kprintf_unlock();
https://nxr.netbsd.org/xref/src/sys/kern/subr_prf.c?r=1.188#265
>How-To-Repeat:
whatever syzbot does -- kernel config for example above:
include "arch/amd64/conf/GENERIC"
options DEBUG
options LOCKDEBUG
makeoptions KMSAN=1
options KMSAN
no options SVS
no options MODULAR
no options MODULAR_DEFAULT_AUTOLOAD
options POOL_NOCACHE
options KMSAN_PANIC
makeoptions KCOV=1
options KCOV
options FAULT
pseudo-device vhci
usb* at vhci?
>Fix:
Yes, please!
(Contact us)
$NetBSD: query-full-pr,v 1.46 2020/01/03 16:35:01 leot Exp $
$NetBSD: gnats_config.sh,v 1.9 2014/08/02 14:16:04 spz Exp $
Copyright © 1994-2020
The NetBSD Foundation, Inc. ALL RIGHTS RESERVED.