queue-6.1/kvm-x86-take-irqfds.lock-when-adding-deleting-irq-bypass-producer.patch

From f1fb088d9cecde5c3066d8ff8846789667519b7d Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@google.com>
Date: Fri, 4 Apr 2025 12:38:19 -0700
Subject: KVM: x86: Take irqfds.lock when adding/deleting IRQ bypass producer

From: Sean Christopherson <seanjc@google.com>

commit f1fb088d9cecde5c3066d8ff8846789667519b7d upstream.

Take irqfds.lock when adding/deleting an IRQ bypass producer to ensure
irqfd->producer isn't modified while kvm_irq_routing_update() is running.
The only lock held when a producer is added/removed is irqbypass's mutex.

Fixes: 872768800652 ("KVM: x86: select IRQ_BYPASS_MANAGER")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20250404193923.1413163-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[sean: account for lack of kvm_x86_call()]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/kvm/x86.c |   19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -13387,16 +13387,22 @@ int kvm_arch_irq_bypass_add_producer(str
 {
 	struct kvm_kernel_irqfd *irqfd =
 		container_of(cons, struct kvm_kernel_irqfd, consumer);
+	struct kvm *kvm = irqfd->kvm;
 	int ret;
 
-	irqfd->producer = prod;
 	kvm_arch_start_assignment(irqfd->kvm);
+
+	spin_lock_irq(&kvm->irqfds.lock);
+	irqfd->producer = prod;
+
 	ret = static_call(kvm_x86_pi_update_irte)(irqfd->kvm,
 					 prod->irq, irqfd->gsi, 1);
-
 	if (ret)
 		kvm_arch_end_assignment(irqfd->kvm);
 
+	spin_unlock_irq(&kvm->irqfds.lock);
+
+
 	return ret;
 }
 
@@ -13406,9 +13412,9 @@ void kvm_arch_irq_bypass_del_producer(st
 	int ret;
 	struct kvm_kernel_irqfd *irqfd =
 		container_of(cons, struct kvm_kernel_irqfd, consumer);
+	struct kvm *kvm = irqfd->kvm;
 
 	WARN_ON(irqfd->producer != prod);
-	irqfd->producer = NULL;
 
 	/*
 	 * When producer of consumer is unregistered, we change back to
@@ -13416,11 +13422,18 @@ void kvm_arch_irq_bypass_del_producer(st
 	 * when the irq is masked/disabled or the consumer side (KVM
 	 * int this case doesn't want to receive the interrupts.
 	*/
+	spin_lock_irq(&kvm->irqfds.lock);
+	irqfd->producer = NULL;
+
+
 	ret = static_call(kvm_x86_pi_update_irte)(irqfd->kvm, prod->irq, irqfd->gsi, 0);
 	if (ret)
 		printk(KERN_INFO "irq bypass consumer (token %p) unregistration"
 		       " fails: %d\n", irqfd->consumer.token, ret);
 
+	spin_unlock_irq(&kvm->irqfds.lock);
+
+
 	kvm_arch_end_assignment(irqfd->kvm);
 }