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AJvYcCXneKaFz44+UPfWilXyH8VryzpTB+9AUFt0Fj/+i8Nv/uClQQNWhDDzHBNgP1+YPVdI4Lv/aXL5gxE1NTUvL3f6LFON X-Gm-Message-State: AOJu0YwiwcVnGypHPCq/k0S7S/dLJ36HejUi03iygZh3611J3QdIP20/ YNAX9dJZK7ASPUUCss58qWhshgyJJ9nEBBoxLxYPC25EeCfpbbdux8CKwZWAyDhNINeLSsDlvdg Chg== X-Google-Smtp-Source: AGHT+IE+ru0espGFuS9wOdmMbFbdZv75qYL5SavI9BTUhtxXWisV6HlT8PRog/sZ2FbZ3VLCGnYpMd1Rd88= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6a02:5a8:b0:6e6:831f:c3f0 with SMTP id 41be03b00d2f7-710b9e10287mr1950a12.11.1718747169797; Tue, 18 Jun 2024 14:46:09 -0700 (PDT) Date: Tue, 18 Jun 2024 14:46:08 -0700 In-Reply-To: <20240614202859.3597745-5-minipli@grsecurity.net> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240614202859.3597745-1-minipli@grsecurity.net> <20240614202859.3597745-5-minipli@grsecurity.net> Message-ID: Subject: Re: [PATCH v3 4/5] KVM: selftests: Test max vCPU IDs corner cases From: Sean Christopherson To: Mathias Krause Cc: Paolo Bonzini , kvm@vger.kernel.org Content-Type: text/plain; charset="us-ascii" On Fri, Jun 14, 2024, Mathias Krause wrote: > The KVM_CREATE_VCPU ioctl ABI had an implicit integer truncation bug, > allowing 2^32 aliases for a vCPU ID by setting the upper 32 bits of a 64 > bit ioctl() argument. > > It also allowed excluding a once set boot CPU ID. > > Verify this no longer works and gets rejected with an error. > > Signed-off-by: Mathias Krause > --- > v3: > - test BOOT_CPU_ID interaction too > > .../kvm/x86_64/max_vcpuid_cap_test.c | 22 +++++++++++++++++-- > 1 file changed, 20 insertions(+), 2 deletions(-) > > diff --git a/tools/testing/selftests/kvm/x86_64/max_vcpuid_cap_test.c b/tools/testing/selftests/kvm/x86_64/max_vcpuid_cap_test.c > index 3cc4b86832fe..c2da915201be 100644 > --- a/tools/testing/selftests/kvm/x86_64/max_vcpuid_cap_test.c > +++ b/tools/testing/selftests/kvm/x86_64/max_vcpuid_cap_test.c > @@ -26,19 +26,37 @@ int main(int argc, char *argv[]) > TEST_ASSERT(ret < 0, > "Setting KVM_CAP_MAX_VCPU_ID beyond KVM cap should fail"); > > + /* Test BOOT_CPU_ID interaction (MAX_VCPU_ID cannot be lower) */ > + if (kvm_has_cap(KVM_CAP_SET_BOOT_CPU_ID)) { > + vm_ioctl(vm, KVM_SET_BOOT_CPU_ID, (void *)MAX_VCPU_ID); > + > + /* Try setting KVM_CAP_MAX_VCPU_ID below BOOT_CPU_ID */ > + ret = __vm_enable_cap(vm, KVM_CAP_MAX_VCPU_ID, MAX_VCPU_ID - 1); > + TEST_ASSERT(ret < 0, > + "Setting KVM_CAP_MAX_VCPU_ID below BOOT_CPU_ID should fail"); > + } > + > /* Set KVM_CAP_MAX_VCPU_ID */ > vm_enable_cap(vm, KVM_CAP_MAX_VCPU_ID, MAX_VCPU_ID); > > - > /* Try to set KVM_CAP_MAX_VCPU_ID again */ > ret = __vm_enable_cap(vm, KVM_CAP_MAX_VCPU_ID, MAX_VCPU_ID + 1); > TEST_ASSERT(ret < 0, > "Setting KVM_CAP_MAX_VCPU_ID multiple times should fail"); > > - /* Create vCPU with id beyond KVM_CAP_MAX_VCPU_ID cap*/ > + /* Create vCPU with id beyond KVM_CAP_MAX_VCPU_ID cap */ > ret = __vm_ioctl(vm, KVM_CREATE_VCPU, (void *)MAX_VCPU_ID); > TEST_ASSERT(ret < 0, "Creating vCPU with ID > MAX_VCPU_ID should fail"); > > + /* Create vCPU with id beyond UINT_MAX */ I changed this comment to /* Create vCPU with bits 63:32 != 0, but an otherwise valid id */ mostly because it's specifically testing the bad truncation of the upper bits, but also because I initially misinterpreted the intent and confused it with the INT_MAX BUILD_BUG_ON(). > + ret = __vm_ioctl(vm, KVM_CREATE_VCPU, (void *)(1L << 32)); > + TEST_ASSERT(ret < 0, "Creating vCPU with ID > UINT_MAX should fail"); > + > + /* Create vCPU with id within bounds */ > + ret = __vm_ioctl(vm, KVM_CREATE_VCPU, (void *)0); > + TEST_ASSERT(ret >= 0, "Creating vCPU with ID 0 should succeed"); > + > + close(ret); > kvm_vm_free(vm); > return 0; > } > -- > 2.30.2 >