linux-kernel - Re: [syzbot? printk?] no WARN_ON() messages printed before "Kernel panic

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190319123500.GA18754@tigerII.localdomain>
Date:   Tue, 19 Mar 2019 21:35:00 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: [syzbot? printk?] no WARN_ON() messages printed before "Kernel
 panic - not syncing: panic_on_warn set ..."

On (03/19/19 09:10), Dmitry Vyukov wrote:

[..]

> In some setups we read out output with "dmesg -w" (should stream
> output as well) in absence of a better solution. Will this be affected
> by SYSLOG_ACTION_CLEAR?

There is a small chance that syslog/devkmsg can be affected

	syslog_clear()
	{
		clear_seq = log_next_seq;
		clear_idx = log_next_idx;
	}

	syslog_print_all()
	{
		...
		seq = clear_seq;
		idx = clear_idx;
		while (seq < log_next_seq) {
		...
			len += msg_print_text(msg, true, time, NULL, 0);
		}
		...
	}

devkmsg also may be affected

	syslog_clear()
	{
		clear_seq = log_next_seq;
		clear_idx = log_next_idx;
	}

	devkmsg_llseek()
	{
	...
		case SEEK_DATA:
			user->idx = clear_idx;
			user->seq = clear_seq;
			break;
	...
	}

user->idx/user->seq then are used in devkmsg poll()/read(). syslog is
more likely to be affected, I think.

	-ss