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([2001:b07:6468:f312:56e1:adff:fed9:caf0]) by smtp.gmail.com with ESMTPSA id g25sm8045149wmh.24.2020.04.17.08.06.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 17 Apr 2020 08:06:11 -0700 (PDT) Subject: Re: [PATCH] KVM: Remove CREATE_IRQCHIP/SET_PIT2 race To: Jon Cargille , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Steve Rutherford References: <20200416191152.259434-1-jcargill@google.com> From: Paolo Bonzini Message-ID: Date: Fri, 17 Apr 2020 17:06:10 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200416191152.259434-1-jcargill@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16/04/20 21:11, Jon Cargille wrote: > From: Steve Rutherford > > Fixes a NULL pointer dereference, caused by the PIT firing an interrupt > before the interrupt table has been initialized. > > SET_PIT2 can race with the creation of the IRQchip. In particular, > if SET_PIT2 is called with a low PIT timer period (after the creation of > the IOAPIC, but before the instantiation of the irq routes), the PIT can > fire an interrupt at an uninitialized table. > > Signed-off-by: Steve Rutherford > Signed-off-by: Jon Cargille > Reviewed-by: Jim Mattson > --- > arch/x86/kvm/x86.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 027dfd278a973..3cc3f673785c8 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -5049,10 +5049,13 @@ long kvm_arch_vm_ioctl(struct file *filp, > r = -EFAULT; > if (copy_from_user(&u.ps, argp, sizeof(u.ps))) > goto out; > + mutex_lock(&kvm->lock); > r = -ENXIO; > if (!kvm->arch.vpit) > - goto out; > + goto set_pit_out; > r = kvm_vm_ioctl_set_pit(kvm, &u.ps); > +set_pit_out: > + mutex_unlock(&kvm->lock); > break; > } > case KVM_GET_PIT2: { > @@ -5072,10 +5075,13 @@ long kvm_arch_vm_ioctl(struct file *filp, > r = -EFAULT; > if (copy_from_user(&u.ps2, argp, sizeof(u.ps2))) > goto out; > + mutex_lock(&kvm->lock); > r = -ENXIO; > if (!kvm->arch.vpit) > - goto out; > + goto set_pit2_out; > r = kvm_vm_ioctl_set_pit2(kvm, &u.ps2); > +set_pit2_out: > + mutex_unlock(&kvm->lock); > break; > } > case KVM_REINJECT_CONTROL: { > Queued, thanks. Paolo