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

[Lorenzo Pieralisi <lpieralisi@kernel.org>]

On Mon, Nov 02, 2026 at 01:32:54PM +0000, Sascha Bischoff wrote:
> 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")
> Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
> ---
>  drivers/irqchip/irq-gic-v5.c | 9 +++++++++
>  1 file changed, 9 insertions(+)

Acked-by: Lorenzo Pieralisi <lpieralisi@kernel.org>

> 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
>