[PATCH 1/4] x86/irq: Ensure PI wakeup handler is unregistered before module unload

From: Sean Christopherson <seanjc@google.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, Paolo Bonzini <pbonzini@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
	Sean Christopherson <seanjc@google.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Subject: [PATCH 1/4] x86/irq: Ensure PI wakeup handler is unregistered before module unload
Date: Fri,  8 Oct 2021 17:11:04 -0700	[thread overview]
Message-ID: <20211009001107.3936588-2-seanjc@google.com> (raw)
In-Reply-To: <20211009001107.3936588-1-seanjc@google.com>

Add a synchronize_rcu() after setting the posted interrupt wakeup handler
to ensure all readers, i.e. in-flight IRQ handlers, see the new handler
before returning to the caller.  If the caller is an exiting module and
is unregistering its handler, failure to wait could result in the IRQ
handler jumping into an unloaded module.

Fixes: f6b3c72c2366 ("x86/irq: Define a global vector for VT-d Posted-Interrupts")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kernel/irq.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index e28f6a5d14f1..20773d315308 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -293,6 +293,7 @@ void kvm_set_posted_intr_wakeup_handler(void (*handler)(void))
 		kvm_posted_intr_wakeup_handler = handler;
 	else
 		kvm_posted_intr_wakeup_handler = dummy_handler;
+	synchronize_rcu();
 }
 EXPORT_SYMBOL_GPL(kvm_set_posted_intr_wakeup_handler);
 
-- 
2.33.0.882.g93a45727a2-goog

