linux-kernel - Re: KASAN: slab-out-of-bounds Read in fbcon_get

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Message-ID: <f4db22f2-53a3-68ed-0f85-9f4541530f5d@redhat.com>
Date:   Thu, 5 Dec 2019 11:22:20 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     syzbot <syzbot+4455ca3b3291de891abc@...kaller.appspotmail.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        DRI <dri-devel@...ts.freedesktop.org>, ghalat@...hat.com,
        Gleb Natapov <gleb@...nel.org>, gwshan@...ux.vnet.ibm.com,
        "H. Peter Anvin" <hpa@...or.com>, James Morris <jmorris@...ei.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        KVM list <kvm@...r.kernel.org>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Russell Currey <ruscur@...sell.cc>,
        Sam Ravnborg <sam@...nborg.org>,
        "Serge E. Hallyn" <serge@...lyn.com>, stewart@...ux.vnet.ibm.com,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Kentaro Takeda <takedakn@...data.co.jp>,
        Thomas Gleixner <tglx@...utronix.de>,
        the arch/x86 maintainers <x86@...nel.org>
Subject: Re: KASAN: slab-out-of-bounds Read in fbcon_get_font

On 05/12/19 11:16, Dmitry Vyukov wrote:
> On Thu, Dec 5, 2019 at 11:13 AM Paolo Bonzini <pbonzini@...hat.com> wrote:
>>
>> On 04/12/19 22:41, syzbot wrote:
>>> syzbot has bisected this bug to:
>>>
>>> commit 2de50e9674fc4ca3c6174b04477f69eb26b4ee31
>>> Author: Russell Currey <ruscur@...sell.cc>
>>> Date:   Mon Feb 8 04:08:20 2016 +0000
>>>
>>>     powerpc/powernv: Remove support for p5ioc2
>>>
>>> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=127a042ae00000
>>> start commit:   76bb8b05 Merge tag 'kbuild-v5.5' of
>>> git://git.kernel.org/p..
>>> git tree:       upstream
>>> final crash:    https://syzkaller.appspot.com/x/report.txt?x=117a042ae00000
>>> console output: https://syzkaller.appspot.com/x/log.txt?x=167a042ae00000
>>> kernel config:  https://syzkaller.appspot.com/x/.config?x=dd226651cb0f364b
>>> dashboard link:
>>> https://syzkaller.appspot.com/bug?extid=4455ca3b3291de891abc
>>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11181edae00000
>>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=105cbb7ae00000
>>>
>>> Reported-by: syzbot+4455ca3b3291de891abc@...kaller.appspotmail.com
>>> Fixes: 2de50e9674fc ("powerpc/powernv: Remove support for p5ioc2")
>>>
>>> For information about bisection process see:
>>> https://goo.gl/tpsmEJ#bisection
>>>
>>
>> Why is everybody being CC'd, even if the bug has nothing to do with the
>> person's subsystem?
> 
> The To list should be intersection of 2 groups of emails: result of
> get_maintainers.pl on the file identified as culprit in the crash
> message + emails extracted from the bisected to commit.

Ah, and because the machine is a KVM guest, kvm_wait appears in a lot of
backtrace and I get to share syzkaller's joy every time. :)

This bisect result is bogus, though Tetsuo found the bug anyway.
Perhaps you can exclude commits that only touch architectures other than
x86?

Paolo