Update cpuid->nent if and only if kvm_vcpu_ioctl_get_cpuid2() succeeds. The sole caller copies @cpuid to userspace only on success, i.e. the existing code effectively does nothing. Arguably, KVM should report the number of entries when returning -E2BIG so that userspace doesn't have to guess the size, but all other similar KVM ioctls() don't report the size either, i.e. userspace is conditioned to guess. Suggested-by: Takahiro Itazuri <itazur@xxxxxxxxxx> Link: https://lore.kernel.org/all/20230410141820.57328-1-itazur@xxxxxxxxxx Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- arch/x86/kvm/cpuid.c | 13 ++++--------- 1 file changed, 4 insertions(+), 9 deletions(-) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 0c9660a07b23..241f554f1764 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -501,20 +501,15 @@ int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid, struct kvm_cpuid_entry2 __user *entries) { - int r; - - r = -E2BIG; if (cpuid->nent < vcpu->arch.cpuid_nent) - goto out; - r = -EFAULT; + return -E2BIG; + if (copy_to_user(entries, vcpu->arch.cpuid_entries, vcpu->arch.cpuid_nent * sizeof(struct kvm_cpuid_entry2))) - goto out; - return 0; + return -EFAULT; -out: cpuid->nent = vcpu->arch.cpuid_nent; - return r; + return 0; } /* Mask kvm_cpu_caps for @leaf with the raw CPUID capabilities of this CPU. */ -- 2.41.0.rc0.172.g3f132b7071-goog
