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[v3,2/5] KVM: x86: Limit check IDs for KVM_SET_BOOT_CPU_ID

Message ID 20240614202859.3597745-3-minipli@grsecurity.net (mailing list archive)
State New, archived
Headers show
Series KVM: Reject vCPU IDs above 2^32 | expand

Commit Message

Mathias Krause June 14, 2024, 8:28 p.m. UTC
Do not accept IDs which are definitely invalid by limit checking the
passed value against KVM_MAX_VCPU_IDS and 'max_vcpu_ids' if it was
already set.

This ensures invalid values, especially on 64-bit systems, don't go
unnoticed and lead to a valid id by chance when truncated by the final

Fixes: 73880c80aa9c ("KVM: Break dependency between vcpu index in vcpus array and vcpu_id.")
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Mathias Krause <minipli@grsecurity.net>
- check against arch.max_vcpu_ids too, if already set (Sean)
- switch to else-if instead of goto (Sean)

 arch/x86/kvm/x86.c | 3 +++
 1 file changed, 3 insertions(+)
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diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 082ac6d95a3a..686606f61dee 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7222,6 +7222,9 @@  int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
 		if (kvm->created_vcpus)
 			r = -EBUSY;
+		else if (arg > KVM_MAX_VCPU_IDS ||
+			 (kvm->arch.max_vcpu_ids && arg > kvm->arch.max_vcpu_ids))
+			r = -EINVAL;
 			kvm->arch.bsp_vcpu_id = arg;