linux-kernel - Re: [ 0.003333] BUG: KASAN: use-after-scope in console

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Date:   Thu, 30 Nov 2017 16:07:30 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Fengguang Wu <fengguang.wu@...el.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        Aleksey Makarov <aleksey.makarov@...aro.org>,
        Nicolas Pitre <nicolas.pitre@...aro.org>,
        Nikitas Angelinas <nikitas.angelinas@...il.com>,
        LKP <lkp@...org>, kasan-dev <kasan-dev@...glegroups.com>
Subject: Re: [ 0.003333] BUG: KASAN: use-after-scope in
 console_unlock+0x605/0xcc0



On 11/30/2017 11:29 AM, Sergey Senozhatsky wrote:
> On (11/30/17 09:16), Dmitry Vyukov wrote:
> [..]
>>> to be honest, this backtrace hardly makes any sense to me.
>>>
>>> vprintk_emit()
>>>  reserve_standard_io_resources()
>>>   __flush_tlb_all()
>>>    vprintk_emit()
>>>     __down_trylock_console_sem()
>>>      wake_up_klogd()
>>>       console_unlock()
>>>
>>> I need some help here.

.config has CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL=y
It's known to cause use-after-scope problems, so printk/console code is likely
has nothing to do with the bug.



>>
>> You can try dirty patch from here:
>> https://groups.google.com/d/msg/kasan-dev/iDb5bhcMBT0/55QzwWaHAwAJ
>> It should make KASAN print the exact variable name and frame where it
>> was allocated.
> 
> would be good if Fengguang can try this out. I can't reproduce the
> problem on my x86 box (linux-next and Linus's trees both work fine
> for me with KASAN + lockdep + TRACE_IRQ).

I suspect you don't have gcc 7. That's is requirement for use-after-scope.

> 	-ss
>