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

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Message-ID: <CACT4Y+ZTM-jjAnnxjgki0vuVDK=-zRhKSAMbfrJVEWf6_v0xKA@mail.gmail.com>
Date:   Thu, 5 Jul 2018 18:20:11 +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 5:27 PM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
> 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.

#syz dup: KASAN: stack-out-of-bounds Read in timerqueue_add