From 6ff53f6a438f72998f56e82e76694a1df9d1ea2c Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 8 Oct 2021 17:11:04 -0700 Subject: [PATCH] x86/irq: Ensure PI wakeup handler is unregistered before module unload Add a synchronize_rcu() after clearing 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. The registration path doesn't require synchronization, as it's the caller's responsibility to not generate interrupts it cares about until after its handler is registered. Fixes: f6b3c72c2366 ("x86/irq: Define a global vector for VT-d Posted-Interrupts") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson Message-Id: <20211009001107.3936588-2-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kernel/irq.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c index e28f6a5d14f1..766ffe3ba313 100644 --- a/arch/x86/kernel/irq.c +++ b/arch/x86/kernel/irq.c @@ -291,8 +291,10 @@ void kvm_set_posted_intr_wakeup_handler(void (*handler)(void)) { if (handler) kvm_posted_intr_wakeup_handler = handler; - else + else { kvm_posted_intr_wakeup_handler = dummy_handler; + synchronize_rcu(); + } } EXPORT_SYMBOL_GPL(kvm_set_posted_intr_wakeup_handler); -- 2.11.0