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

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Message-ID: <bf93410c-7e59-a679-c00d-5333a9879128@redhat.com>
Date:   Thu, 5 Dec 2019 12:29:20 +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 12:27, Dmitry Vyukov wrote:
> Oh, you mean the final bisection crash. Indeed it contains a kvm frame
> and it turns out to be a bug in syzkaller code that indeed
> misattributed it to kvm instead of netfilter.
> Should be fixed now, you may read the commit message for details:
> https://github.com/google/syzkaller/commit/4fb74474cf0af2126be3a8989d770c3947ae9478
> 
> Overall this "making sense out of kernel output" task is the ultimate
> insanity, you may skim through this file to get a taste of amount of
> hardcoding and special corner cases that need to be handled:
> https://github.com/google/syzkaller/blob/master/pkg/report/linux.go
> And this is never done, such "exception from exception corner case"
> things pop up every week. There is always something to shuffle and
> tune. It only keeps functioning due to 500+ test cases for all
> possible insane kernel outputs:
> https://github.com/google/syzkaller/tree/master/pkg/report/testdata/linux/report
> https://github.com/google/syzkaller/tree/master/pkg/report/testdata/linux/guilty
> 
> So thanks for persisting and questioning! We are getting better with
> each new test.

Thanks to you!  I "complain" because I know you're so responsive. :)

Paolo