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KVM: x86: Add a helper to retrieve userspace address from kvm_device_attr

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Add a helper to handle converting the u64 userspace address embedded in
struct kvm_device_attr into a userspace pointer, it's all too easy to
forget the intermediate "unsigned long" cast as well as the truncation
check.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2022-01-27 07:31:53 -08:00 • committed by Paolo Bonzini
parent dd4516aee3
commit 56f289a8d2
1 changed files with 14 additions and 6 deletions
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20
arch/x86/kvm/x86.c
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@ -4332,7 +4332,15 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
break; break;
} }
return r; return r;
}
static inline void __user *kvm_get_attr_addr(struct kvm_device_attr *attr)
{
void __user *uaddr = (void __user*)(unsigned long)attr->addr;
if ((u64)(unsigned long)uaddr != attr->addr)
return ERR_PTR(-EFAULT);
return uaddr;
} }
long kvm_arch_dev_ioctl(struct file *filp, long kvm_arch_dev_ioctl(struct file *filp,
@ -5025,11 +5033,11 @@ static int kvm_arch_tsc_has_attr(struct kvm_vcpu *vcpu,
static int kvm_arch_tsc_get_attr(struct kvm_vcpu *vcpu, static int kvm_arch_tsc_get_attr(struct kvm_vcpu *vcpu,
struct kvm_device_attr *attr) struct kvm_device_attr *attr)
{ {
u64 __user *uaddr = (u64 __user *)(unsigned long)attr->addr; u64 __user *uaddr = kvm_get_attr_addr(attr);
int r; int r;
if ((u64)(unsigned long)uaddr != attr->addr) if (IS_ERR(uaddr))
return -EFAULT; return PTR_ERR(uaddr);
switch (attr->attr) { switch (attr->attr) {
case KVM_VCPU_TSC_OFFSET: case KVM_VCPU_TSC_OFFSET:
@ -5048,12 +5056,12 @@ static int kvm_arch_tsc_get_attr(struct kvm_vcpu *vcpu,
static int kvm_arch_tsc_set_attr(struct kvm_vcpu *vcpu, static int kvm_arch_tsc_set_attr(struct kvm_vcpu *vcpu,
struct kvm_device_attr *attr) struct kvm_device_attr *attr)
{ {
u64 __user *uaddr = (u64 __user *)(unsigned long)attr->addr; u64 __user *uaddr = kvm_get_attr_addr(attr);
struct kvm *kvm = vcpu->kvm; struct kvm *kvm = vcpu->kvm;
int r; int r;
if ((u64)(unsigned long)uaddr != attr->addr) if (IS_ERR(uaddr))
return -EFAULT; return PTR_ERR(uaddr);
switch (attr->attr) { switch (attr->attr) {
case KVM_VCPU_TSC_OFFSET: { case KVM_VCPU_TSC_OFFSET: {