From: Siddharth Chandrasekaran <sidcha@amazon.de>
To: Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
<x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>
Cc: Siddharth Chandrasekaran <sidcha@amazon.de>,
<kvm@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: [PATCH v2] KVM: x86: Hoist input checks in kvm_add_msr_filter()
Date: Tue, 4 May 2021 10:25:59 +0200 [thread overview]
Message-ID: <20210504082600.3668-1-sidcha@amazon.de> (raw)
In ioctl KVM_X86_SET_MSR_FILTER, input from user space is validated
after a memdup_user(). For invalid inputs we'd memdup and then call
kfree unnecessarily. Hoist input validation to avoid kfree altogether.
Signed-off-by: Siddharth Chandrasekaran <sidcha@amazon.de>
---
arch/x86/kvm/x86.c | 26 +++++++-------------------
1 file changed, 7 insertions(+), 19 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ee0dc58ac3a5..c4fc0c46927a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5390,14 +5390,18 @@ static void kvm_free_msr_filter(struct kvm_x86_msr_filter *msr_filter)
static int kvm_add_msr_filter(struct kvm_x86_msr_filter *msr_filter,
struct kvm_msr_filter_range *user_range)
{
- struct msr_bitmap_range range;
unsigned long *bitmap = NULL;
size_t bitmap_size;
- int r;
if (!user_range->nmsrs)
return 0;
+ if (user_range->flags & ~(KVM_MSR_FILTER_READ | KVM_MSR_FILTER_WRITE))
+ return -EINVAL;
+
+ if (!user_range->flags)
+ return -EINVAL;
+
bitmap_size = BITS_TO_LONGS(user_range->nmsrs) * sizeof(long);
if (!bitmap_size || bitmap_size > KVM_MSR_FILTER_MAX_BITMAP_SIZE)
return -EINVAL;
@@ -5406,31 +5410,15 @@ static int kvm_add_msr_filter(struct kvm_x86_msr_filter *msr_filter,
if (IS_ERR(bitmap))
return PTR_ERR(bitmap);
- range = (struct msr_bitmap_range) {
+ msr_filter->ranges[msr_filter->count] = (struct msr_bitmap_range) {
.flags = user_range->flags,
.base = user_range->base,
.nmsrs = user_range->nmsrs,
.bitmap = bitmap,
};
-
- if (range.flags & ~(KVM_MSR_FILTER_READ | KVM_MSR_FILTER_WRITE)) {
- r = -EINVAL;
- goto err;
- }
-
- if (!range.flags) {
- r = -EINVAL;
- goto err;
- }
-
- /* Everything ok, add this range identifier. */
- msr_filter->ranges[msr_filter->count] = range;
msr_filter->count++;
return 0;
-err:
- kfree(bitmap);
- return r;
}
static int kvm_vm_ioctl_set_msr_filter(struct kvm *kvm, void __user *argp)
--
2.17.1
Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879
reply other threads:[~2021-05-04 8:26 UTC|newest]
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