From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
Add slots_lock around kvm_flush_shadow_all(). kvm_gmem_release() via
fput() and kvm_mmu_notifier_release() via mmput() can be called
simultaneously on process exit because vhost, /dev/vhost_{net, vsock}, can
delay the call to release mmu_notifier, kvm_mmu_notifier_release() by its
kernel thread. Vhost uses get_task_mm() and mmput() for the kernel thread
to access process memory. mmput() can defer after closing the file.
kvm_flush_shadow_all() and kvm_gmem_release() can be called simultaneously.
With TDX KVM, HKID releasing by kvm_flush_shadow_all() and private memory
releasing by kvm_gmem_release() can race. Add slots_lock to
kvm_mmu_notifier_release().
Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
---
virt/kvm/kvm_main.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 49380cd62367..4855d0b7a859 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -927,9 +927,16 @@ static void kvm_mmu_notifier_release(struct mmu_notifier *mn,
struct kvm *kvm = mmu_notifier_to_kvm(mn);
int idx;
+ /*
+ * Avoide race with kvm_gmem_release().
+ * This function is called via mmu notifier, mmu_release().
+ * kvm_gmem_release() is called via fput() on process exit.
+ */
+ mutex_lock(&kvm->slots_lock);
idx = srcu_read_lock(&kvm->srcu);
kvm_flush_shadow_all(kvm);
srcu_read_unlock(&kvm->srcu, idx);
+ mutex_unlock(&kvm->slots_lock);
}
static const struct mmu_notifier_ops kvm_mmu_notifier_ops = {
--
2.25.1
