[PATCH v2] LoongArch: KVM: Fix TOCTOU race on pv_features
Tao Cui <[email protected]>
| Newsgroups | dev.linux.lists.loongarch,org.kernel.vger.kvm,org.kernel.vger.linux-kernel |
|---|---|
| Message-ID | <[email protected]> |
From: Tao Cui <[email protected]> The check-then-set on kvm->arch.pv_features in kvm_loongarch_cpucfg_set_attr() is lockless, so two vCPUs can race past the validation and set different values. Add a spinlock to serialize it. Signed-off-by: Tao Cui <[email protected]> --- Changes in v2: use a spinlock instead of a cmpxchg loop (Bibo Mao). Link: https://lore.kernel.org/all/[email protected]/ arch/loongarch/include/asm/kvm_host.h | 2 ++ arch/loongarch/kvm/vcpu.c | 6 +++++- arch/loongarch/kvm/vm.c | 1 + 3 files changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h index 23cfbecebbd7..cdbbd90e0584 100644 --- a/arch/loongarch/include/asm/kvm_host.h +++ b/arch/loongarch/include/asm/kvm_host.h @@ -128,6 +128,8 @@ struct kvm_arch { struct kvm_phyid_map *phyid_map; /* Enabled PV features */ unsigned long pv_features; + /* Serializes pv_features updates */ + spinlock_t pv_features_lock; /* Supported KVM features */ unsigned long kvm_features; diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c index 20c207d80e31..551ed39b2d1f 100644 --- a/arch/loongarch/kvm/vcpu.c +++ b/arch/loongarch/kvm/vcpu.c @@ -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_features_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_features_lock); return -EINVAL; + } kvm->arch.pv_features = val | LOONGARCH_PV_FEAT_UPDATED; + spin_unlock(&kvm->arch.pv_features_lock); return 0; default: return -ENXIO; diff --git a/arch/loongarch/kvm/vm.c b/arch/loongarch/kvm/vm.c index 1317c718f896..b984cc54f305 100644 --- a/arch/loongarch/kvm/vm.c +++ b/arch/loongarch/kvm/vm.c @@ -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_features_lock); kvm_init_vmcs(kvm); kvm_vm_init_features(kvm); -- 2.43.0