linux-kernel - Re: KASAN: use-after-scope Read in __hrtimer_run

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Message-ID: <CACT4Y+aOvjaHHmKiKZzZAMqv3NRsXEXcfN3+v7LzrKqWyM1e4Q@mail.gmail.com>
Date:   Wed, 4 Jul 2018 17:27:36 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     syzbot <syzbot+7f73a81393d3b3777fb0@...kaller.appspotmail.com>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: KASAN: use-after-scope Read in __hrtimer_run_queues

On Wed, Jul 4, 2018 at 5:20 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> On Wed, 4 Jul 2018, syzbot wrote:
>
>> Hello,
>>
>> syzbot found the following crash on:
>>
>> HEAD commit:    2bdea157b999 Merge branch 'sctp-fully-support-for-dscp-and..
>> git tree:       bpf-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=14339f42400000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=f62553dc846b0692
>> dashboard link: https://syzkaller.appspot.com/bug?extid=7f73a81393d3b3777fb0
>> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
>>
>> Unfortunately, I don't have any reproducer for this crash yet.
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+7f73a81393d3b3777fb0@...kaller.appspotmail.com
>>
>> ==================================================================
>> BUG: KASAN: use-after-scope in lookup_object lib/debugobjects.c:157 [inline]
>> BUG: KASAN: use-after-scope in debug_object_deactivate+0x425/0x450
>> lib/debugobjects.c:540
>> Read of size 8 at addr ffff88019d1a5ec0 by task syz-executor3/13445
>
> I don't see how lib/debugobjects.c:157 would be a valid use after scope
> issue. The one in line 540 makes no sense either.

Hi Thomas,

They all don't make sense:
https://groups.google.com/d/msg/syzkaller-bugs/A-S5Rfn5bwQ/dFvmNcmyAAAJ

One of them says "stack overflow", so there seems to be a serious
system corruption that now leads to assorted nonsensical crashes. And
this seems to be a very recent change.