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KVM: selftests: Test max vCPU IDs corner cases

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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 <minipli@grsecurity.net>
Link: https://lore.kernel.org/r/20240614202859.3597745-5-minipli@grsecurity.net
[sean: tweak assert message+comment for 63:32!=0 testcase]
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Mathias Krause 2024-06-14 22:28:58 +02:00 committed by Sean Christopherson
parent d29bf2ca14
commit 4b451a5780
1 changed files with 20 additions and 2 deletions
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22
tools/testing/selftests/kvm/x86_64/max_vcpuid_cap_test.c
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@ -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 bits 63:32 != 0, but an otherwise valid id */
ret = __vm_ioctl(vm, KVM_CREATE_VCPU, (void *)(1L << 32));
TEST_ASSERT(ret < 0, "Creating vCPU with ID[63:32] != 0 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;
}