From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
syzbot+904752567107eefb728c@syzkaller.appspotmail.com
Subject: Re: [PATCH] KVM: x86: Initialize tdp_level during vCPU creation
Date: Thu, 28 May 2020 12:46:04 -0700 [thread overview]
Message-ID: <20200528194604.GE30353@linux.intel.com> (raw)
In-Reply-To: <20200527162933.GE24461@linux.intel.com>
On Wed, May 27, 2020 at 09:29:33AM -0700, Sean Christopherson wrote:
> On Wed, May 27, 2020 at 06:17:57PM +0200, Paolo Bonzini wrote:
> > On 27/05/20 10:54, Sean Christopherson wrote:
> > > Initialize vcpu->arch.tdp_level during vCPU creation to avoid consuming
> > > garbage if userspace calls KVM_RUN without first calling KVM_SET_CPUID.
> > >
> > > Fixes: e93fd3b3e89e9 ("KVM: x86/mmu: Capture TDP level when updating CPUID")
> > > Reported-by: syzbot+904752567107eefb728c@syzkaller.appspotmail.com
> > > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> > > ---
> > > arch/x86/kvm/x86.c | 1 +
> > > 1 file changed, 1 insertion(+)
> > >
> > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > > index b226fb8abe41b..01a6304056197 100644
> > > --- a/arch/x86/kvm/x86.c
> > > +++ b/arch/x86/kvm/x86.c
> > > @@ -9414,6 +9414,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
> > > fx_init(vcpu);
> > >
> > > vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
> > > + vcpu->arch.tdp_level = kvm_x86_ops.get_tdp_level(vcpu);
> > >
> > > vcpu->arch.pat = MSR_IA32_CR_PAT_DEFAULT;
> >
> > Queued, it is probably a good idea to add a selftests testcase for this
> > (it's even okay if it doesn't use the whole selftests infrastructure and
> > invokes KVM_CREATE_VM/KVM_CREATE_VCPU/KVM_RUN manually).
>
> Ya. syzbot is hitting a #GP due to NULL pointer during debugfs on the exact
> same sequence. I haven't been able to reproduce that one (have yet to try
> syzbot's exact config), but it's another example of a "dumb" test hitting
> meaningful bugs.
So we already have a selftest for this scenario, test_zero_memory_regions()
in set_memory_region_test.c. Embarrassingly, I wrote the darn thing, I'm
just really neglectful when it comes to running selftests.
I'll looking into writing a script to run all selftests with a single
command, unless someone already has one laying around?
next prev parent reply other threads:[~2020-05-28 19:46 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-27 8:54 [PATCH] KVM: x86: Initialize tdp_level during vCPU creation Sean Christopherson
2020-05-27 10:03 ` Vitaly Kuznetsov
2020-05-27 16:15 ` Paolo Bonzini
2020-05-27 16:23 ` Sean Christopherson
2020-05-27 16:56 ` Paolo Bonzini
2020-05-28 2:27 ` Sean Christopherson
2020-05-27 16:17 ` Paolo Bonzini
2020-05-27 16:29 ` Sean Christopherson
2020-05-27 16:56 ` Paolo Bonzini
2020-05-27 17:06 ` Sean Christopherson
2020-05-28 19:46 ` Sean Christopherson [this message]
2020-05-29 7:46 ` Vitaly Kuznetsov
2020-05-29 13:06 ` Sean Christopherson
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