[PATCH v2] irqchip/mst-intc: validate the DT interrupt range

[Pengpeng Hou <hppiscas@163.com>]

The driver takes an inclusive interrupt range from the device tree
without checking its endpoints. A reversed range wraps the unsigned
count calculation, and a range larger than MST_INTC_MAX_IRQS exceeds the
controller capacity used by the driver.

Reject these ranges before calculating nr_irqs or creating the domain.
Check the difference after ordering the endpoints so the validation
itself cannot wrap.

The issue was found by our static-analysis tool.

Fixes: ad4c938c92af ("irqchip/irq-mst: Add MStar interrupt controller support")
Reviewed-by: Radu Rendec <radu@rendec.net>
Assisted-by: gpt 5
Signed-off-by: Pengpeng Hou <hppiscas@163.com>
---
Changes since v1:
https://lore.kernel.org/all/20260722041443.10020-1-pengpeng@iscas.ac.cn/
Describe the missing DT range validation directly, keep the condition on
one line, and add the introducing Fixes tag as Thomas requested.

 drivers/irqchip/irq-mst-intc.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/irqchip/irq-mst-intc.c b/drivers/irqchip/irq-mst-intc.c
index b5335f6fd6d6..1070de5de8cc 100644
--- a/drivers/irqchip/irq-mst-intc.c
+++ b/drivers/irqchip/irq-mst-intc.c
@@ -263,6 +263,9 @@ static int __init mst_intc_of_init(struct device_node *dn,
 	    of_property_read_u32_index(dn, "mstar,irqs-map-range", 1, &irq_end))
 		return -EINVAL;
 
+	if (irq_end < irq_start || irq_end - irq_start >= MST_INTC_MAX_IRQS)
+		return -EINVAL;
+
 	cd = kzalloc_obj(*cd);
 	if (!cd)
 		return -ENOMEM;

base-commit: 518e5b794c06c0f0eb40df3e202274a66202c137
-- 
2.50.1 (Apple Git-155)