linux-kernel - [PATCH 1/3] genirq/irqdomain: Check for existing mapping in irq_domain

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Date:   Thu, 12 Sep 2019 09:44:07 +0000
From:   "Sverdlin, Alexander (Nokia - DE/Ulm)" <alexander.sverdlin@...ia.com>
To:     Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Grant Likely <grant.likely@...retlab.ca>
CC:     "Sverdlin, Alexander (Nokia - DE/Ulm)" <alexander.sverdlin@...ia.com>,
        Mark Brown <broonie@...nsource.wolfsonmicro.com>,
        Jon Hunter <jonathanh@...dia.com>,
        "Glavinic-Pecotic, Matija (EXT - DE/Ulm)" 
        <matija.glavinic-pecotic.ext@...ia.com>,
        "Adamski, Krzysztof (Nokia - PL/Wroclaw)" 
        <krzysztof.adamski@...ia.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: [PATCH 1/3] genirq/irqdomain: Check for existing mapping in
 irq_domain_associate()

From: Alexander Sverdlin <alexander.sverdlin@...ia.com>

irq_domain_associate() is the only place where irq_find_mapping() can be
used reliably (under irq_domain_mutex) to make a decision if the mapping
shall be created or not. Other calls to irq_find_mapping() (not under
any lock) cannot be used for this purpose and lead to race conditions in
particular inside irq_create_mapping().

Give the callers of irq_domain_associate() an ability to detect existing
domain reliably by examining the return value.

Cc: stable@...r.kernel.org
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@...ia.com>
---
 kernel/irq/irqdomain.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index 3078d0e..7bc07b6 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -532,6 +532,7 @@ int irq_domain_associate(struct irq_domain *domain, unsigned int virq,
 			 irq_hw_number_t hwirq)
 {
 	struct irq_data *irq_data = irq_get_irq_data(virq);
+	unsigned int eirq;
 	int ret;
 
 	if (WARN(hwirq >= domain->hwirq_max,
@@ -543,6 +544,16 @@ int irq_domain_associate(struct irq_domain *domain, unsigned int virq,
 		return -EINVAL;
 
 	mutex_lock(&irq_domain_mutex);
+
+	/* Check if mapping already exists */
+	eirq = irq_find_mapping(domain, hwirq);
+	if (eirq) {
+		mutex_unlock(&irq_domain_mutex);
+		pr_debug("%s: conflicting mapping for hwirq 0x%x\n",
+			 domain->name, (int)hwirq);
+		return -EBUSY;
+	}
+
 	irq_data->hwirq = hwirq;
 	irq_data->domain = domain;
 	if (domain->ops->map) {
-- 
2.4.6