linux-kernel - [PATCH] genirq/irqdomain: Don't try to free an interrupt that has no mapping

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Date:   Sun, 29 Nov 2020 13:55:51 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] genirq/irqdomain: Don't try to free an interrupt that has no mapping

When an interrupt allocation fails for N interrupts, it is pretty
common for the error handling code to free the same number of interrupts,
no matter how many interrupts have actually been allocated.

This may result in the domain freeing code to be unexpectedly called
for interrupts that have no mapping in that domain. Things end pretty
badly.

Instead, add some checks to irq_domain_free_irqs_hierarchy() to make
sure that we don't follow the hierarchy if no mapping exists for
a given interrupt.

Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 kernel/irq/irqdomain.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index cf8b374b892d..4d8f5a661c2a 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -1370,8 +1370,14 @@ static void irq_domain_free_irqs_hierarchy(struct irq_domain *domain,
 					   unsigned int irq_base,
 					   unsigned int nr_irqs)
 {
-	if (domain->ops->free)
-		domain->ops->free(domain, irq_base, nr_irqs);
+	int i;
+
+	if (!domain->ops->free)
+		return;
+
+	for (i = 0; i < nr_irqs; i++)
+		if (irq_domain_get_irq_data(domain, irq_base + i))
+			domain->ops->free(domain, irq_base + i, 1);
 }

 int irq_domain_alloc_irqs_hierarchy(struct irq_domain *domain,
-- 
2.29.2