pcmcia: avoid buffer overflow in pcmcia_setup_isa_irq

commit 127c03cd upstream.

NR_IRQS may be as low as 16, causing a (harmless?) buffer overflow in
pcmcia_setup_isa_irq():

static u8 pcmcia_used_irq[NR_IRQS];

...

		if ((try < 32) && pcmcia_used_irq[irq])
			continue;

This is read-only, so if this address would be non-zero, it would just
mean we would not attempt an IRQ >= NR_IRQS -- which would fail anyway!
And as request_irq() fails for an irq >= NR_IRQS, the setting code path:

			pcmcia_used_irq[irq]++;

is never reached as well.
Reported-by: Christoph Fritz <chf.fritz@googlemail.com>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Christoph Fritz <chf.fritz@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/pcmcia/pcmcia_resource.c

@@ -39,7 +39,7 @@ module_param(io_speed, int, 0444);
 #ifdef CONFIG_PCMCIA_PROBE
 #include <asm/irq.h>
 /* mask of IRQs already reserved by other cards, we should avoid using them */
-static u8 pcmcia_used_irq[NR_IRQS];
+static u8 pcmcia_used_irq[32];
 #endif
 
 
@@ -719,6 +719,9 @@ int pcmcia_request_irq(struct pcmcia_device *p_dev, irq_req_t *req)
 		for (try = 0; try < 64; try++) {
 			irq = try % 32;
 
+			if (irq > NR_IRQS)
+				continue;
+
 			/* marked as available by driver, and not blocked by userspace? */
 			if (!((mask >> irq) & 1))
 				continue;