linux-kernel - Re: [lkp] [printk.c] ea0639c4d5: BUG:recent_printk

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Date:   Fri, 2 Dec 2016 11:05:58 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     kernel test robot <xiaolong.ye@...el.com>
Cc:     Sebastian Duda <sebastian.duda@....de>, linux-kernel@...cs.fau.de,
        Tobias Baumeister <tobias.baumeister@....de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Borislav Petkov <bp@...e.de>, Tejun Heo <tj@...nel.org>,
        Thierry Reding <treding@...dia.com>,
        open list <linux-kernel@...r.kernel.org>, lkp@...org
Subject: Re: [lkp] [printk.c]  ea0639c4d5: BUG:recent_printk_recursion

On Fri 2016-12-02 01:12:32, kernel test robot wrote:
> 
> FYI, we noticed the following commit:
> 
> commit: ea0639c4d5c700ad63c0ace6a7a17877aac5b4c2 ("printk.c: removed unnecessary code")
> url: https://github.com/0day-ci/linux/commits/Sebastian-Duda/printk-c-removed-unnecessary-code/20161130-225006
> 
> 
> in testcase: trinity
> with following parameters:
> 
> 	runtime: 300s
> 
> test-description: Trinity is a linux system call fuzz tester.
> test-url: http://codemonkey.org.uk/projects/trinity/
> 
> 
> on test machine: qemu-system-i386 -enable-kvm -m 256M
> 
> caused below changes:
> 
> 
> +-------------------------------------------------------+------------+------------+
> |                                                       | ded6e842cf | ea0639c4d5 |
> +-------------------------------------------------------+------------+------------+
> | boot_successes                                        | 19         | 8          |
> | boot_failures                                         | 3          | 49         |

I am not surprised. The patch breaks counting of the space
needed to print the message. It is likely to cause buffer
overflows. I have already nacked it, see
https://lkml.kernel.org/r/20161130102231.GE24060@pathway.suse.cz

Anyway, thanks for testing.

Best Regards,
Petr