KVM: Reduce stack usage in kvm_vcpu_ioctl()

(cherry picked from commit fa3795a7308df099f0f2c9e5ca2c20a5ff65bdc4)

Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 46474af54763c9062c9fb5328780c75f0dc5ad29..e4ce72570910fcde18ae9bbec4ad3fa93ce1360a 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1118,6 +1118,8 @@ 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;
@@ -1165,25 +1167,28 @@ 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;
@@ -1264,25 +1269,28 @@ 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;
@@ -1292,6 +1300,8 @@ out_free2:
                r = kvm_arch_vcpu_ioctl(filp, ioctl, arg);
        }
 out:
+       kfree(fpu);
+       kfree(kvm_sregs);
        return r;
 }