[PATCH v2 01/10] irqchip/gic-v5: Reject SPIs not backed by an IRS

[Sascha Bischoff <sascha.bischoff@arm.com>]

It is possible to build a multi-IRS GICv5 system where there are gaps
in the global SPI range that are not backed by any IRS. In the current
incarnation, this results in dereferencing a null pointer.

Reject cases where the firmware attempts to use those SPIs during IRQ
allocation by catching the case where there is no chip_data associated
with the irq (meaning that there is no IRS to back it). Spit out a
warning about broken firmware when this is encountered as it shouldn't
be using non-existent SPIs in the first place.

Fixes: 5cb1b6dab2def ("irqchip/gic-v5: Add GICv5 IRS/SPI support")
Acked-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
---
 drivers/irqchip/irq-gic-v5.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/irqchip/irq-gic-v5.c b/drivers/irqchip/irq-gic-v5.c
index 8c0303af71e7d..f3cce2bd28cc3 100644
--- a/drivers/irqchip/irq-gic-v5.c
+++ b/drivers/irqchip/irq-gic-v5.c
@@ -727,6 +727,15 @@ static int gicv5_irq_spi_domain_alloc(struct irq_domain *domain, unsigned int vi
 
 	irqd = irq_desc_get_irq_data(irq_to_desc(virq));
 	chip_data = gicv5_irs_lookup_by_spi_id(hwirq);
+	/*
+	 * The global SPI range may contain IDs not covered by any IRS, i.e., it
+	 * may have gaps, in which case there is no IRS to back the SPI. Catch
+	 * broken firmware trying to use any of those SPIs.
+	 */
+	if (!chip_data) {
+		pr_warn("Firmware bug! Unimplemented SPI (0x%lx)!\n", hwirq);
+		return -EINVAL;
+	}
 
 	irq_domain_set_info(domain, virq, hwirq, &gicv5_spi_irq_chip, chip_data,
 			    handle_fasteoi_irq, NULL, NULL);

-- 
2.34.1