[PATCH] irqchip/gic: prevent buffer overflow in gic_ipi_send_mask()

[Sergey Shtylyov]

ARM GIC arch v2 spec claims support for just 8 CPU interfaces.  However,
looking at the GIC driver's irq_set_affinity() method, it seems that the
passed CPU mask may contain the logical CPU #s beyond 8, and that method
filters them out before reading gic_cpu_map[], bailing out with -EINVAL.
Such check should also be performed in the ipi_send_mask() method where
it uses for_each_cpu(), in order to prevent accessing beyond the end of
gic_cpu_map[] there as well...

Found by Linux Verification Center (linuxtesting.org) with the Svace static
analysis tool.

Fixes: 384a290283fd ("ARM: gic: use a private mapping for CPU target interfaces")
Signed-off-by: Sergey Shtylyov <s.shtylyov@xxxxxx>

---
The patch is against the irq/core branch of the tip.git repo...

 drivers/irqchip/irq-gic.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Index: tip/drivers/irqchip/irq-gic.c
===================================================================
--- tip.orig/drivers/irqchip/irq-gic.c
+++ tip/drivers/irqchip/irq-gic.c
@@ -832,8 +832,11 @@ static void gic_ipi_send_mask(struct irq
 	gic_lock_irqsave(flags);
 
 	/* Convert our logical CPU mask into a physical one. */
-	for_each_cpu(cpu, mask)
+	for_each_cpu(cpu, mask) {
+		if (cpu >= NR_GIC_CPU_IF)
+			break;
 		map |= gic_cpu_map[cpu];
+	}
 
 	/*
 	 * Ensure that stores to Normal memory are visible to the