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LoongArch: KVM: Fix TOCTOU race on pv_features

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In kvm_loongarch_cpucfg_set_attr() the check-then-set on
kvm->arch.pv_features is lockless, so two vCPUs can race past the
validation and set different values. Add a spinlock to protect it.

Cc: stable@vger.kernel.org
Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Tao Cui <cuitao@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
Tao Cui 2026-09-04 21:45:13 +08:00 committed by Huacai Chen
parent 501514d6eb
commit 9296375902
3 changed files with 7 additions and 1 deletions
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1
arch/loongarch/include/asm/kvm_host.h
View File

@ -125,6 +125,7 @@ struct kvm_arch {
unsigned int pte_shifts[MAX_PGTABLE_LEVELS];
unsigned int root_level;
spinlock_t phyid_map_lock;
spinlock_t pv_setting_lock;
struct kvm_phyid_map *phyid_map;
/* Enabled PV features */
unsigned long pv_features;

6
arch/loongarch/kvm/vcpu.c
View File

@ -1165,10 +1165,14 @@ static int kvm_loongarch_cpucfg_set_attr(struct kvm_vcpu *vcpu,
return -EINVAL;
/* All vCPUs need set the same PV features */
spin_lock(&kvm->arch.pv_setting_lock);
if ((kvm->arch.pv_features & LOONGARCH_PV_FEAT_UPDATED)
&& ((kvm->arch.pv_features & valid) != val))
&& ((kvm->arch.pv_features & valid) != val)) {
spin_unlock(&kvm->arch.pv_setting_lock);
return -EINVAL;
}
kvm->arch.pv_features = val | LOONGARCH_PV_FEAT_UPDATED;
spin_unlock(&kvm->arch.pv_setting_lock);
return 0;
default:
return -ENXIO;

1
arch/loongarch/kvm/vm.c
View File

@ -76,6 +76,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
return -ENOMEM;
}
spin_lock_init(&kvm->arch.phyid_map_lock);
spin_lock_init(&kvm->arch.pv_setting_lock);
kvm_init_vmcs(kvm);
kvm_vm_init_features(kvm);