KVM: x86: Don't re-acquire SRCU lock in complete_emulated_io()

Don't re-acquire SRCU in complete_emulated_io() now that KVM acquires the lock in kvm_arch_vcpu_ioctl_run(). More importantly, don't overwrite vcpu->srcu_idx. If the index acquired by complete_emulated_io() differs from the one acquired by kvm_arch_vcpu_ioctl_run(), KVM will effectively leak a lock and hang if/when synchronize_srcu() is invoked for the relevant grace period. Fixes: 8d25b7b ("KVM: x86: pull kvm->srcu read-side to kvm_arch_vcpu_ioctl_run") Cc: [email protected] Signed-off-by: Sean Christopherson <[email protected]> Reviewed-by: Maxim Levitsky <[email protected]> Message-Id: <[email protected]> Signed-off-by: Paolo Bonzini <[email protected]>
josf · Apr 21, 2022 · 2d08935 · 2d08935
1 parent 012c722
commit 2d08935
Showing 1 changed file with 1 addition and 6 deletions.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
@@ -10387,12 +10387,7 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
 
 static inline int complete_emulated_io(struct kvm_vcpu *vcpu)
 {
-	int r;
-
-	vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
-	r = kvm_emulate_instruction(vcpu, EMULTYPE_NO_DECODE);
-	srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
-	return r;
+	return kvm_emulate_instruction(vcpu, EMULTYPE_NO_DECODE);
 }
 
 static int complete_emulated_pio(struct kvm_vcpu *vcpu)