KVM: Reduce stack usage in kvm_arch_vcpu_ioctl()

[sheng: fix KVM_GET_LAPIC using wrong size]

Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Sheng Yang <sheng.yang@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 15 insertions, 8 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 87d434228fe2..f1b0223c4088 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1542,28 +1542,33 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
         struct kvm_vcpu *vcpu = filp->private_data;
         void __user *argp = (void __user *)arg;
         int r;
+        struct kvm_lapic_state *lapic = NULL;
 
         switch (ioctl) {
         case KVM_GET_LAPIC: {
-                struct kvm_lapic_state lapic;
+                lapic = kzalloc(sizeof(struct kvm_lapic_state), GFP_KERNEL);
 
-                memset(&lapic, 0, sizeof lapic);
-                r = kvm_vcpu_ioctl_get_lapic(vcpu, &lapic);
+                r = -ENOMEM;
+                if (!lapic)
+                        goto out;
+                r = kvm_vcpu_ioctl_get_lapic(vcpu, lapic);
                 if (r)
                         goto out;
                 r = -EFAULT;
-                if (copy_to_user(argp, &lapic, sizeof lapic))
+                if (copy_to_user(argp, lapic, sizeof(struct kvm_lapic_state)))
                         goto out;
                 r = 0;
                 break;
         }
         case KVM_SET_LAPIC: {
-                struct kvm_lapic_state lapic;
-
+                lapic = kmalloc(sizeof(struct kvm_lapic_state), GFP_KERNEL);
+                r = -ENOMEM;
+                if (!lapic)
+                        goto out;
                 r = -EFAULT;
-                if (copy_from_user(&lapic, argp, sizeof lapic))
+                if (copy_from_user(lapic, argp, sizeof(struct kvm_lapic_state)))
                         goto out;
-                r = kvm_vcpu_ioctl_set_lapic(vcpu, &lapic);;
+                r = kvm_vcpu_ioctl_set_lapic(vcpu, lapic);
                 if (r)
                         goto out;
                 r = 0;
@@ -1661,6 +1666,8 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
                 r = -EINVAL;
         }
 out:
+        if (lapic)
+                kfree(lapic);
         return r;
 }