linux-kernel - Re: KASAN: out-of-bounds Write in nested_sync_vmcs12_to

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Message-ID: <3fed5719-9b30-fe69-9b2d-3584440759d1@redhat.com>
Date:   Tue, 21 Apr 2020 15:38:38 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     syzbot <syzbot+6ad11779184a3afe9f7e@...kaller.appspotmail.com>,
        bp@...en8.de, hpa@...or.com, jmattson@...gle.com, joro@...tes.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, sean.j.christopherson@...el.com,
        syzkaller-bugs@...glegroups.com, tglx@...utronix.de,
        vkuznets@...hat.com, wanpengli@...cent.com, x86@...nel.org
Subject: Re: KASAN: out-of-bounds Write in nested_sync_vmcs12_to_shadow

On 21/04/20 02:15, syzbot wrote:
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+6ad11779184a3afe9f7e@...kaller.appspotmail.com
> 
> ==================================================================
> BUG: KASAN: out-of-bounds in copy_vmcs12_to_enlightened arch/x86/kvm/vmx/nested.c:1820 [inline]
> BUG: KASAN: out-of-bounds in nested_sync_vmcs12_to_shadow+0x49e3/0x4a60 arch/x86/kvm/vmx/nested.c:2000
> Write of size 2 at addr ffffc90004db72e8 by task syz-executor.4/8294
> 
> CPU: 1 PID: 8294 Comm: syz-executor.4 Not tainted 5.7.0-rc1-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  <IRQ>
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x188/0x20d lib/dump_stack.c:118
>  print_address_description.constprop.0.cold+0x5/0x315 mm/kasan/report.c:382
>  __kasan_report.cold+0x35/0x4d mm/kasan/report.c:511
>  kasan_report+0x33/0x50 mm/kasan/common.c:625
>  copy_vmcs12_to_enlightened arch/x86/kvm/vmx/nested.c:1820 [inline]
>  nested_sync_vmcs12_to_shadow+0x49e3/0x4a60 arch/x86/kvm/vmx/nested.c:2000
>  </IRQ>

That's a weird stack trace for a reproducer that is doing operations on
/dev/fb0.  What's going on?

Paolo