linux-kernel - Re: KASAN: use-after-free Read in do_general

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Date:   Mon, 28 May 2018 13:25:24 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>,
        syzbot <syzbot+a1264132fc103340628f@...kaller.appspotmail.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        KVM list <kvm@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: KASAN: use-after-free Read in do_general_protection

On 26/05/2018 11:29, Dmitry Vyukov wrote:
> KASAN: stack-out-of-bounds Read in do_general_protection
> KASAN: slab-out-of-bounds Read in vmx_vcpu_run
> KASAN: use-after-scope Read in vmx_vcpu_run
> KASAN: stack-out-of-bounds Write in notify_die
> 
> See full info at:
> https://syzkaller.appspot.com/bug?extid=a1264132fc103340628f
> 
> 
> There seems to be 2 problems:
> 
> 1. msr_write_intercepted doing something notoriously bad.

The faulting line is

        msr_bitmap = to_vmx(vcpu)->loaded_vmcs->msr_bitmap;

so I suppose to_vmx(vcpu)->loaded_vmcs is bogus?  That seems like "just"
a corruption of the struct kvm_vcpu, because the loaded_vmcs field is
pointing elsewhere inside the same struct.

Paolo