[PATCH 1/2] LoongArch: KVM: Make kvm_get_vcpu_by_cpuid() more robust

[Huacai Chen]

kvm_get_vcpu_by_cpuid() takes a cpuid parameter whose type is int, so
cpuid can be negative. Let kvm_get_vcpu_by_cpuid() return NULL for this
case so as to make it more robust.

This fix an out-of-bounds access to kvm_arch::phyid_map::phys_map[].

Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 73516e9da512adc ("LoongArch: KVM: Add vcpu mapping from physical cpuid")
Reported-by: Aurelien Jarno <aurel32@xxxxxxxxxx>
Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1131431
Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
---
 arch/loongarch/kvm/vcpu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
index 8ffd50a470e6..831f381a8fd1 100644
--- a/arch/loongarch/kvm/vcpu.c
+++ b/arch/loongarch/kvm/vcpu.c
@@ -588,6 +588,9 @@ struct kvm_vcpu *kvm_get_vcpu_by_cpuid(struct kvm *kvm, int cpuid)
 {
 	struct kvm_phyid_map *map;
 
+	if (cpuid < 0)
+		return NULL;
+
 	if (cpuid >= KVM_MAX_PHYID)
 		return NULL;
 
-- 
2.52.0