linux-kernel - Re: NULL-ptr deref in kvm_arch_vcpu

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Message-ID: <CACT4Y+bs6Q2uvG1PXE-HL0jj3f+q9487S0M_wv0v=B9Ws8SAUw@mail.gmail.com>
Date:   Tue, 30 Aug 2016 15:08:19 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Robert Święcki <robert@...ecki.net>,
        LKML <linux-kernel@...r.kernel.org>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: NULL-ptr deref in kvm_arch_vcpu_ioctl under AMD CPUs

On Mon, Aug 29, 2016 at 2:02 PM, Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> On 19/08/2016 02:16, Dmitry Vyukov wrote:
>> > > This seems non-exploitable due to mmap_min_addr, so I guess it should
>> > > be treated just as a regular bug
>> >
>> > Probably fixed by commit 4c5ea0a9cd02 ("locking/static_key: Fix
>> > concurrent static_key_slow_inc()", 2016-06-21).  There should be no
>> > outstanding syzkaller reports for KVM now!
>>
>> Thanks for the update. I will try to reenable kvm fuzzing on my
>> syzkaller instances.
>> Just to make sure, you mean all bugs prefixed with kvm: here, right?
>> https://github.com/google/syzkaller/wiki/Found-Bugs
>
> Yes.  These are the relevant commits:
>
> b21629da120   kvm: x86: avoid warning on repeated KVM_SET_TSS_ADDR
> 83676e92389   KVM: x86: avoid vmalloc(0) in the KVM_SET_CPUID
> 78e546c824f   KVM: fail KVM_SET_VCPU_EVENTS with invalid exception number
> c622a3c21ed   KVM: irqfd: fix NULL pointer dereference in kvm_irq_map_gsi
> f8c1b85b252   KVM: x86: avoid vmalloc(0) in the KVM_SET_CPUID
> d14bdb553f9   KVM: x86: fix OOPS after invalid KVM_SET_DEBUGREGS
> 250715a6171   KVM: x86: protect KVM_CREATE_PIT/KVM_CREATE_PIT2 with kvm->lock
> 4c5ea0a9cd0   locking/static_key: Fix concurrent static_key_slow_inc()
>
> The last one is responsible for most if not all of the OOPses with
> threads.


I've started fuzzing kvm again. No crashes so far.