linux-kernel - [PATCH 2/3] KVM: x86: Make filter arg for set_msr

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Date:   Mon, 17 Oct 2022 20:45:40 +0200
From:   Alexander Graf <graf@...zon.com>
To:     <kvm@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        "Andrew Randrianasulu" <randrianasulu@...il.com>,
        Thomas Huth <thuth@...hat.com>
Subject: [PATCH 2/3] KVM: x86: Make filter arg for set_msr_filter()

In the next patch we want to introduce a second caller to
set_msr_filter() which constructs its own filter list on the stack.
Refactor the original function so it takes it as argument instead of
reading it through copy_from_user().

Signed-off-by: Alexander Graf <graf@...zon.com>
---
 arch/x86/kvm/x86.c | 31 +++++++++++++++++--------------
 1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b0c47b41c264..19f060ce577f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6399,26 +6399,22 @@ static int kvm_add_msr_filter(struct kvm_x86_msr_filter *msr_filter,
 	return 0;
 }
 
-static int kvm_vm_ioctl_set_msr_filter(struct kvm *kvm, void __user *argp)
+static int kvm_vm_ioctl_set_msr_filter(struct kvm *kvm,
+				       struct kvm_msr_filter *filter)
 {
-	struct kvm_msr_filter __user *user_msr_filter = argp;
 	struct kvm_x86_msr_filter *new_filter, *old_filter;
-	struct kvm_msr_filter filter;
 	bool default_allow;
 	bool empty = true;
 	int r = 0;
 	u32 i;
 
-	if (copy_from_user(&filter, user_msr_filter, sizeof(filter)))
-		return -EFAULT;
-
-	if (filter.flags & ~KVM_MSR_FILTER_DEFAULT_DENY)
+	if (filter->flags & ~KVM_MSR_FILTER_DEFAULT_DENY)
 		return -EINVAL;
 
-	for (i = 0; i < ARRAY_SIZE(filter.ranges); i++)
-		empty &= !filter.ranges[i].nmsrs;
+	for (i = 0; i < ARRAY_SIZE(filter->ranges); i++)
+		empty &= !filter->ranges[i].nmsrs;
 
-	default_allow = !(filter.flags & KVM_MSR_FILTER_DEFAULT_DENY);
+	default_allow = !(filter->flags & KVM_MSR_FILTER_DEFAULT_DENY);
 	if (empty && !default_allow)
 		return -EINVAL;
 
@@ -6426,8 +6422,8 @@ static int kvm_vm_ioctl_set_msr_filter(struct kvm *kvm, void __user *argp)
 	if (!new_filter)
 		return -ENOMEM;
 
-	for (i = 0; i < ARRAY_SIZE(filter.ranges); i++) {
-		r = kvm_add_msr_filter(new_filter, &filter.ranges[i]);
+	for (i = 0; i < ARRAY_SIZE(filter->ranges); i++) {
+		r = kvm_add_msr_filter(new_filter, &filter->ranges[i]);
 		if (r) {
 			kvm_free_msr_filter(new_filter);
 			return r;
@@ -6872,9 +6868,16 @@ long kvm_arch_vm_ioctl(struct file *filp,
 	case KVM_SET_PMU_EVENT_FILTER:
 		r = kvm_vm_ioctl_set_pmu_event_filter(kvm, argp);
 		break;
-	case KVM_X86_SET_MSR_FILTER:
-		r = kvm_vm_ioctl_set_msr_filter(kvm, argp);
+	case KVM_X86_SET_MSR_FILTER: {
+		struct kvm_msr_filter __user *user_msr_filter = argp;
+		struct kvm_msr_filter filter;
+
+		if (copy_from_user(&filter, user_msr_filter, sizeof(filter)))
+			return -EFAULT;
+
+		r = kvm_vm_ioctl_set_msr_filter(kvm, &filter);
 		break;
+	}
 	default:
 		r = -ENOTTY;
 	}
-- 
2.37.1




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