linux-kernel - Re: [lkp-robot] [x86/mm/ptdump] 243b72aae2: WARNING:at_arch/x86/mm/dump_pagetables.c:#note

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Date:   Tue, 28 Feb 2017 09:19:23 +0800
From:   Ye Xiaolong <xiaolong.ye@...el.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexander Potapenko <glider@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        Tobias Regnery <tobias.regnery@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>, lkp@...org,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [lkp-robot] [x86/mm/ptdump] 243b72aae2:
 WARNING:at_arch/x86/mm/dump_pagetables.c:#note_page

On 02/28, Masami Hiramatsu wrote:
>On Mon, 27 Feb 2017 16:01:34 +0300
>Andrey Ryabinin <aryabinin@...tuozzo.com> wrote:
>
>> On 02/27/2017 04:03 AM, kernel test robot wrote:
>> > 
>> > FYI, we noticed the following commit:
>> > 
>> > commit: 243b72aae28ca1032284028323bb81c9235b15c9 ("x86/mm/ptdump: Optimize check for W+X mappings for CONFIG_KASAN=y")
>> > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
>> 
>> ...
>> > 
>> > caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
>> > 
>> > 
>> > +-----------------------------------------------------+------------+------------+
>> > |                                                     | 5b1ad68f9b | 243b72aae2 |
>> > +-----------------------------------------------------+------------+------------+
>> > | boot_successes                                      | 0          | 0          |
>> > | boot_failures                                       | 8          | 6          |
>> > | BUG:KASAN:slab-out-of-bounds                        | 8          | 6          |
>> > | WARNING:at_arch/x86/mm/dump_pagetables.c:#note_page | 0          | 6          |
>> > +-----------------------------------------------------+------------+------------+
>> 
>> Ok, I reproduced this, but it's definitely caused *not* by 243b72aae28.
>> This WARN is also reproducible on the parent commit 5b1ad68f9b.
>> The only difference here is that on parent one needs dozens of seconds to reach this WARNING.
>> It seems that this time difference somehow confused the robot.
>> 
>> As for the warning itself, it caused by kprobes. krpobe code use module_alloc() which
>> creates these RWX mappings.
>> I'm not sure how to fix this as AFAIK kprobes actually need RWX mapping.
>
>Thanks! I also noticed this issue. I actually have a plan to make kprobes with R+X mappings (as ftrace does).
>I'll queue this on my TODO list.
>

Good to know that, feel free to ask me to verify your fix if needed.

Thanks,
Xiaolong
>
>
>-- 
>Masami Hiramatsu <mhiramat@...nel.org>