linux-kernel - Re: kernel BUG at arch/x86/kvm/mmu/mmu.c:LINE! (2)

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Message-ID: <20200527001213.GA31696@linux.intel.com>
Date:   Tue, 26 May 2020 17:12:13 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     syzbot <syzbot+904752567107eefb728c@...kaller.appspotmail.com>
Cc:     bp@...en8.de, eesposit@...hat.com, gregkh@...uxfoundation.org,
        hpa@...or.com, jmattson@...gle.com, joro@...tes.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, pbonzini@...hat.com, rafael@...nel.org,
        syzkaller-bugs@...glegroups.com, tglx@...utronix.de,
        vkuznets@...hat.com, wanpengli@...cent.com, x86@...nel.org
Subject: Re: kernel BUG at arch/x86/kvm/mmu/mmu.c:LINE! (2)

On Tue, May 26, 2020 at 02:13:19PM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    c11d28ab Add linux-next specific files for 20200522
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=153b5016100000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=3f6dbdea4159fb66
> dashboard link: https://syzkaller.appspot.com/bug?extid=904752567107eefb728c
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11510cba100000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=129301e2100000
> 
> The bug was bisected to:
> 
> commit 63d04348371b7ea4a134bcf47c79763d969e9168
> Author: Paolo Bonzini <pbonzini@...hat.com>
> Date:   Tue Mar 31 22:42:22 2020 +0000
> 
>     KVM: x86: move kvm_create_vcpu_debugfs after last failure point
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1226e8ee100000
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=1126e8ee100000
> console output: https://syzkaller.appspot.com/x/log.txt?x=1626e8ee100000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+904752567107eefb728c@...kaller.appspotmail.com
> Fixes: 63d04348371b ("KVM: x86: move kvm_create_vcpu_debugfs after last failure point")
> 
> L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for details.
> ------------[ cut here ]------------
> kernel BUG at arch/x86/kvm/mmu/mmu.c:3722!

The bisection has a completely different signature, it's likely a different
bug.  I'll take a look at both.