KVM: Reduce stack usage in kvm_vcpu_ioctl()

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

1 files changed, 28 insertions, 18 deletions

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 5eb96c7c8d7..0309571fcb2 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1126,6 +1126,8 @@ static long kvm_vcpu_ioctl(struct file *filp,
         struct kvm_vcpu *vcpu = filp->private_data;
         void __user *argp = (void __user *)arg;
         int r;
+        struct kvm_fpu *fpu = NULL;
+        struct kvm_sregs *kvm_sregs = NULL;
 
         if (vcpu->kvm->mm != current->mm)
                 return -EIO;
@@ -1173,25 +1175,28 @@ out_free2:
                 break;
         }
         case KVM_GET_SREGS: {
-                struct kvm_sregs kvm_sregs;
-
-                memset(&kvm_sregs, 0, sizeof kvm_sregs);
-                r = kvm_arch_vcpu_ioctl_get_sregs(vcpu, &kvm_sregs);
+                kvm_sregs = kzalloc(sizeof(struct kvm_sregs), GFP_KERNEL);
+                r = -ENOMEM;
+                if (!kvm_sregs)
+                        goto out;
+                r = kvm_arch_vcpu_ioctl_get_sregs(vcpu, kvm_sregs);
                 if (r)
                         goto out;
                 r = -EFAULT;
-                if (copy_to_user(argp, &kvm_sregs, sizeof kvm_sregs))
+                if (copy_to_user(argp, kvm_sregs, sizeof(struct kvm_sregs)))
                         goto out;
                 r = 0;
                 break;
         }
         case KVM_SET_SREGS: {
-                struct kvm_sregs kvm_sregs;
-
+                kvm_sregs = kmalloc(sizeof(struct kvm_sregs), GFP_KERNEL);
+                r = -ENOMEM;
+                if (!kvm_sregs)
+                        goto out;
                 r = -EFAULT;
-                if (copy_from_user(&kvm_sregs, argp, sizeof kvm_sregs))
+                if (copy_from_user(kvm_sregs, argp, sizeof(struct kvm_sregs)))
                         goto out;
-                r = kvm_arch_vcpu_ioctl_set_sregs(vcpu, &kvm_sregs);
+                r = kvm_arch_vcpu_ioctl_set_sregs(vcpu, kvm_sregs);
                 if (r)
                         goto out;
                 r = 0;
@@ -1272,25 +1277,28 @@ out_free2:
                 break;
         }
         case KVM_GET_FPU: {
-                struct kvm_fpu fpu;
-
-                memset(&fpu, 0, sizeof fpu);
-                r = kvm_arch_vcpu_ioctl_get_fpu(vcpu, &fpu);
+                fpu = kzalloc(sizeof(struct kvm_fpu), GFP_KERNEL);
+                r = -ENOMEM;
+                if (!fpu)
+                        goto out;
+                r = kvm_arch_vcpu_ioctl_get_fpu(vcpu, fpu);
                 if (r)
                         goto out;
                 r = -EFAULT;
-                if (copy_to_user(argp, &fpu, sizeof fpu))
+                if (copy_to_user(argp, fpu, sizeof(struct kvm_fpu)))
                         goto out;
                 r = 0;
                 break;
         }
         case KVM_SET_FPU: {
-                struct kvm_fpu fpu;
-
+                fpu = kmalloc(sizeof(struct kvm_fpu), GFP_KERNEL);
+                r = -ENOMEM;
+                if (!fpu)
+                        goto out;
                 r = -EFAULT;
-                if (copy_from_user(&fpu, argp, sizeof fpu))
+                if (copy_from_user(fpu, argp, sizeof(struct kvm_fpu)))
                         goto out;
-                r = kvm_arch_vcpu_ioctl_set_fpu(vcpu, &fpu);
+                r = kvm_arch_vcpu_ioctl_set_fpu(vcpu, fpu);
                 if (r)
                         goto out;
                 r = 0;
@@ -1300,6 +1308,8 @@ out_free2:
                 r = kvm_arch_vcpu_ioctl(filp, ioctl, arg);
         }
 out:
+        kfree(fpu);
+        kfree(kvm_sregs);
         return r;
 }