From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.6 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0EBC2C43381 for ; Mon, 18 Mar 2019 12:08:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C724A20857 for ; Mon, 18 Mar 2019 12:08:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="elFN+5hc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727672AbfCRMIF (ORCPT ); Mon, 18 Mar 2019 08:08:05 -0400 Received: from mail-io1-f68.google.com ([209.85.166.68]:45478 "EHLO mail-io1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726435AbfCRMIC (ORCPT ); Mon, 18 Mar 2019 08:08:02 -0400 Received: by mail-io1-f68.google.com with SMTP id x9so14131664iog.12 for ; Mon, 18 Mar 2019 05:08:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=pgMq4kSF7AJCXsw0h1AN0keHFBk6j94wEh+uaN+IV6s=; b=elFN+5hcMTxTdkwGRKhElE1anRf4ueX+tpZ6EYF8hZkMd05OlZnad7HqI77yg9tHDU es47Aqg80TiqBbmP7uNZVp0b8ebi4uH+AlsQ6S1UACMxdJh54w0hne/ADwK3udtYb9z/ XKbGO4H+MaUXU8Z/3Ryzqc/7N9e0cKfKqv91ZaKe05xEBWMlkyQjYPR7xtx4MRlCbOfR 7C90Q+jiA/4+6tfEtYqHsid6T3ZVOsIEQUkGgZv2/+p/8bOPIgyVBWv2FK1aVDm6O3cc 35+4oG+aK3ynwnCGlPVLP/DI+bVzrHXR1K6wGXdo1ba+dDs7PA5GKGaM1eOyuedtfsc8 W8jQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=pgMq4kSF7AJCXsw0h1AN0keHFBk6j94wEh+uaN+IV6s=; b=Ywx14POIObWcAb6OxhlxuZXKzzw2JqG0FygphbCYKMR02R0cZx+9S13PYp1ectLPn9 bsf2ttVC/4ZkseXQ4ZWl/35FkFFQ8K51VxkLkpOqmdWgv4xIcMmib0Ij1uN0Pn9OD2Bh NxaJcwKFwA3CZUMH6y1Nbpsps7bKrCNM+MjK3duhlODI/QXW7i2qdceIFKh9SbajA4Yz 9xJYwJ2sKzBb3RDefh6Ol52xZOF4O7dCEVW+w1UQhuvM5t7VWIlgOqMCTv/TpJWCd1Oi uCEVDpsp8dHzN4Vl5lFwKAjON7a1Gm5i1ly6HZFc7z5dOTm1121rSGUQR5kgCVqiTzn0 WCpQ== X-Gm-Message-State: APjAAAUoMEFuCFq5BCfz/jc9B6ZQDx/8RDSByzZHVdxfcxeLP3UvBxzf wP1Va5jQNgq+gYQS9VtrN2KgnL+R7O9Fwa44PW2mMA== X-Google-Smtp-Source: APXvYqwbXZgu7cwGSJHBv9oe6XxXrHhroBBsvIe5ifOZiwEPXlPunl43GbZSdXt7IMmzx8QsvnF3gG33C5dwZsB3cxY= X-Received: by 2002:a5d:834a:: with SMTP id q10mr10197004ior.271.1552910881669; Mon, 18 Mar 2019 05:08:01 -0700 (PDT) MIME-Version: 1.0 References: <2a48dee7-b649-65a4-be5d-8b3374013cee@i-love.sakura.ne.jp> <201903180527.x2I5RQVp009981@www262.sakura.ne.jp> In-Reply-To: <201903180527.x2I5RQVp009981@www262.sakura.ne.jp> From: Dmitry Vyukov Date: Mon, 18 Mar 2019 13:07:49 +0100 Message-ID: Subject: Re: [syzbot? printk?] no WARN_ON() messages printed before "Kernel panic - not syncing: panic_on_warn set ..." To: Tetsuo Handa Cc: Sergey Senozhatsky , Petr Mladek , Sergey Senozhatsky , LKML , syzkaller Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 18, 2019 at 6:27 AM Tetsuo Handa wrote: > > Dmitry Vyukov wrote: > > > Then, we need to find what test is changing console_loglevel. > > > Maybe add debug BUG_ON() in linux-next.git using CONFIG_DEBUG_AID_FOR_SYZBOT ? > > > > Is there a single place to catch this? I could run syzkaller locally > > first with the check. > > > > There is no such place. But not so many places change permanently. > For x86, you can test with below patch applied. > > --- > drivers/tty/sysrq.c | 1 + > kernel/printk/printk.c | 3 +++ > kernel/sysctl.c | 23 ++++++++++++++++++++++- > 3 files changed, 26 insertions(+), 1 deletion(-) > > diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c > index fa0ce7d..ad73520 100644 > --- a/drivers/tty/sysrq.c > +++ b/drivers/tty/sysrq.c > @@ -91,6 +91,7 @@ static void sysrq_handle_loglevel(int key) > i = key - '0'; > console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; > pr_info("Loglevel set to %d\n", i); > + WARN_ONCE(i < CONSOLE_LOGLEVEL_DEFAULT, "Reducing console_loglevel to %d", i); > console_loglevel = i; > } > static struct sysrq_key_op sysrq_loglevel_op = { > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c > index 02ca827..70d1f8c 100644 > --- a/kernel/printk/printk.c > +++ b/kernel/printk/printk.c > @@ -1533,11 +1533,13 @@ int do_syslog(int type, char __user *buf, int len, int source) > case SYSLOG_ACTION_CONSOLE_OFF: > if (saved_console_loglevel == LOGLEVEL_DEFAULT) > saved_console_loglevel = console_loglevel; > + WARN_ONCE(minimum_console_loglevel < CONSOLE_LOGLEVEL_DEFAULT, "Reducing console_loglevel to %d", minimum_console_loglevel); > console_loglevel = minimum_console_loglevel; > break; > /* Enable logging to console */ > case SYSLOG_ACTION_CONSOLE_ON: > if (saved_console_loglevel != LOGLEVEL_DEFAULT) { > + WARN_ONCE(saved_console_loglevel < CONSOLE_LOGLEVEL_DEFAULT, "Reducing console_loglevel to %d", saved_console_loglevel); > console_loglevel = saved_console_loglevel; > saved_console_loglevel = LOGLEVEL_DEFAULT; > } > @@ -1548,6 +1550,7 @@ int do_syslog(int type, char __user *buf, int len, int source) > return -EINVAL; > if (len < minimum_console_loglevel) > len = minimum_console_loglevel; > + WARN_ONCE(len < CONSOLE_LOGLEVEL_DEFAULT, "Reducing console_loglevel to %d", len); > console_loglevel = len; > /* Implicitly re-enable logging to console */ > saved_console_loglevel = LOGLEVEL_DEFAULT; > diff --git a/kernel/sysctl.c b/kernel/sysctl.c > index b3df3ab..2170421 100644 > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -273,6 +273,27 @@ static int sysrq_sysctl_handler(struct ctl_table *table, int write, > int sysctl_legacy_va_layout; > #endif > > +static int proc_dointvec_loglevel(struct ctl_table *table, int write, > + void __user *buffer, size_t *lenp, loff_t *ppos) > +{ > + if (write && buffer && *lenp) { > + size_t len = *lenp; > + char *kbuf, *p; > + > + if (len > PAGE_SIZE - 1) > + len = PAGE_SIZE - 1; > + p = kbuf = memdup_user_nul(buffer, len); > + if (IS_ERR(kbuf)) > + return PTR_ERR(kbuf); > + while (*p && (*p < '0' || *p > '9')) > + p++; > + len = *p ? strtoul(p, &p, 10) : CONSOLE_LOGLEVEL_DEFAULT; > + WARN_ONCE(len < CONSOLE_LOGLEVEL_DEFAULT, "Reducing console_loglevel to %d", (int) len); > + kfree(kbuf); > + } > + return proc_dointvec(table, write, buffer, lenp, ppos); > +} > + > /* The default sysctl tables: */ > > static struct ctl_table sysctl_base_table[] = { > @@ -839,7 +860,7 @@ static int sysrq_sysctl_handler(struct ctl_table *table, int write, > .data = &console_loglevel, > .maxlen = 4*sizeof(int), > .mode = 0644, > - .proc_handler = proc_dointvec, > + .proc_handler = proc_dointvec_loglevel, > }, > { > .procname = "printk_ratelimit", > -- > 1.8.3.1 Thanks. Running this for 10 mins I only got a bunch of these, so at least none of these WARNs does not trigger immediately. But I will continue running it. WARNING in schedule_bh kernel BUG at ./include/linux/mm.h:LINE! WARNING in vkms_vblank_simulate general protection fault in xfrmi_decode_session INFO: task hung in corrupted kernel BUG at drivers/android/binder_alloc.c:LINE! BUG: unable to handle kernel NULL pointer dereference in drm_atomic_helper_commit_modeset_disables INFO: task hung in __rq_qos_throttle WARNING in sk_stream_kill_queues