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AJvYcCUpnZ5dACFdZ4cn6LyQeSTodHgWVD4aNmJGdvIlYo1DmUMy3gP9YBihzfNMbmC6PcOZaLsoMfxffgwZHoE=@vger.kernel.org X-Gm-Message-State: AOJu0Yw6EZDTyMzTULOuMmY+yjFaPubXqG2orD76XnrT10C6rpmByIS3 WlcOcN/qwnuVGb6t6NGeQCAoDe7NIrRtG0YBhlIdaE/20ZPq0ituS8P9hXkqwX6M45nG+ZQuAUs UKQ== X-Google-Smtp-Source: AGHT+IHyeNuhBnW0QqO63/mQpYNWJJkaFMu8OIJPcWZdkHxnOXShSpmfKQvcDgQI94dU6/2l/aAm83E3Rco= X-Received: from pjbsz15.prod.google.com ([2002:a17:90b:2d4f:b0:2ef:8a7b:195c]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:54cb:b0:2ee:8e75:4aeb with SMTP id 98e67ed59e1d1-2f548ec9267mr36225691a91.17.1736807398604; Mon, 13 Jan 2025 14:29:58 -0800 (PST) Date: Mon, 13 Jan 2025 14:29:57 -0800 In-Reply-To: <20250113222740.1481934-2-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250113222740.1481934-1-seanjc@google.com> <20250113222740.1481934-2-seanjc@google.com> Message-ID: Subject: Re: [PATCH 1/5] KVM: x86: Reject Hyper-V's SEND_IPI hypercalls if local APIC isn't in-kernel From: Sean Christopherson To: Vitaly Kuznetsov , Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Dongjie Zou Content-Type: text/plain; charset="us-ascii" On Mon, Jan 13, 2025, Sean Christopherson wrote: > Advertise support for Hyper-V's SEND_IPI and SEND_IPI_EX hypercalls if and > only if the local API is emulated/virtualized by KVM, and explicitly reject > said hypercalls if the local APIC is emulated in userspace, i.e. don't rely > on userspace to opt-in to KVM_CAP_HYPERV_ENFORCE_CPUID. > > Rejecting SEND_IPI and SEND_IPI_EX fixes a NULL-pointer dereference if > Hyper-V enlightenments are exposed to the guest without an in-kernel local > APIC: > > dump_stack+0xbe/0xfd > __kasan_report.cold+0x34/0x84 > kasan_report+0x3a/0x50 > __apic_accept_irq+0x3a/0x5c0 > kvm_hv_send_ipi.isra.0+0x34e/0x820 > kvm_hv_hypercall+0x8d9/0x9d0 > kvm_emulate_hypercall+0x506/0x7e0 > __vmx_handle_exit+0x283/0xb60 > vmx_handle_exit+0x1d/0xd0 > vcpu_enter_guest+0x16b0/0x24c0 > vcpu_run+0xc0/0x550 > kvm_arch_vcpu_ioctl_run+0x170/0x6d0 > kvm_vcpu_ioctl+0x413/0xb20 > __se_sys_ioctl+0x111/0x160 > do_syscal1_64+0x30/0x40 > entry_SYSCALL_64_after_hwframe+0x67/0xd1 > > Note, checking the sending vCPU is sufficient, as the per-VM irqchip_mode > can't be modified after vCPUs are created, i.e. if one vCPU has an > in-kernel local APIC, then all vCPUs have an in-kernel local APIC. > > Reported-by: Dongjie Zou > Fixes: 214ff83d4473 ("KVM: x86: hyperv: implement PV IPI send hypercalls") > Fixes: 2bc39970e932 ("x86/kvm/hyper-v: Introduce KVM_GET_SUPPORTED_HV_CPUID") > Cc: stable@vger.kernel Argh, I missed the ".org". Paolo, if you end up applying this instead of me, can you fixup the email?