linux-kernel - [PATCH v2 1/8] irqbypass: Drop pointless and misleading THIS

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Message-ID: <20250516230734.2564775-2-seanjc@google.com>
Date: Fri, 16 May 2025 16:07:27 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	"Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>, 
	Alex Williamson <alex.williamson@...hat.com>
Cc: kvm@...r.kernel.org, virtualization@...ts.linux.dev, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Kevin Tian <kevin.tian@...el.com>, Oliver Upton <oliver.upton@...ux.dev>, 
	David Matlack <dmatlack@...gle.com>, Like Xu <like.xu.linux@...il.com>, 
	Binbin Wu <binbin.wu@...ux.intel.com>, Yong He <alexyonghe@...cent.com>
Subject: [PATCH v2 1/8] irqbypass: Drop pointless and misleading THIS_MODULE get/put

Drop irqbypass.ko's superfluous and misleading get/put calls on
THIS_MODULE.  A module taking a reference to itself is useless; no amount
of checks will prevent doom and destruction if the caller hasn't already
guaranteed the liveliness of the module (this goes for any module).  E.g.
if try_module_get() fails because irqbypass.ko is being unloaded, then the
kernel has already hit a use-after-free by virtue of executing code whose
lifecycle is tied to irqbypass.ko.

Reviewed-by: Kevin Tian <kevin.tian@...el.com>
Acked-by: Michael S. Tsirkin <mst@...hat.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 virt/lib/irqbypass.c | 20 --------------------
 1 file changed, 20 deletions(-)

diff --git a/virt/lib/irqbypass.c b/virt/lib/irqbypass.c
index 28fda42e471b..080c706f3b01 100644
--- a/virt/lib/irqbypass.c
+++ b/virt/lib/irqbypass.c
@@ -92,9 +92,6 @@ int irq_bypass_register_producer(struct irq_bypass_producer *producer)
 
 	might_sleep();
 
-	if (!try_module_get(THIS_MODULE))
-		return -ENODEV;
-
 	mutex_lock(&lock);
 
 	list_for_each_entry(tmp, &producers, node) {
@@ -120,7 +117,6 @@ int irq_bypass_register_producer(struct irq_bypass_producer *producer)
 	return 0;
 out_err:
 	mutex_unlock(&lock);
-	module_put(THIS_MODULE);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(irq_bypass_register_producer);
@@ -142,9 +138,6 @@ void irq_bypass_unregister_producer(struct irq_bypass_producer *producer)
 
 	might_sleep();
 
-	if (!try_module_get(THIS_MODULE))
-		return; /* nothing in the list anyway */
-
 	mutex_lock(&lock);
 
 	list_for_each_entry(tmp, &producers, node) {
@@ -159,13 +152,10 @@ void irq_bypass_unregister_producer(struct irq_bypass_producer *producer)
 		}
 
 		list_del(&producer->node);
-		module_put(THIS_MODULE);
 		break;
 	}
 
 	mutex_unlock(&lock);
-
-	module_put(THIS_MODULE);
 }
 EXPORT_SYMBOL_GPL(irq_bypass_unregister_producer);
 
@@ -188,9 +178,6 @@ int irq_bypass_register_consumer(struct irq_bypass_consumer *consumer)
 
 	might_sleep();
 
-	if (!try_module_get(THIS_MODULE))
-		return -ENODEV;
-
 	mutex_lock(&lock);
 
 	list_for_each_entry(tmp, &consumers, node) {
@@ -216,7 +203,6 @@ int irq_bypass_register_consumer(struct irq_bypass_consumer *consumer)
 	return 0;
 out_err:
 	mutex_unlock(&lock);
-	module_put(THIS_MODULE);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(irq_bypass_register_consumer);
@@ -238,9 +224,6 @@ void irq_bypass_unregister_consumer(struct irq_bypass_consumer *consumer)
 
 	might_sleep();
 
-	if (!try_module_get(THIS_MODULE))
-		return; /* nothing in the list anyway */
-
 	mutex_lock(&lock);
 
 	list_for_each_entry(tmp, &consumers, node) {
@@ -255,12 +238,9 @@ void irq_bypass_unregister_consumer(struct irq_bypass_consumer *consumer)
 		}
 
 		list_del(&consumer->node);
-		module_put(THIS_MODULE);
 		break;
 	}
 
 	mutex_unlock(&lock);
-
-	module_put(THIS_MODULE);
 }
 EXPORT_SYMBOL_GPL(irq_bypass_unregister_consumer);
-- 
2.49.0.1112.g889b7c5bd8-goog