drivers/char: for hpet, add count checking, and ~0UL instead of -1

  use ~0UL for unsigned long variable initialization, instead of -1.

  add check for hdp->hd_nirqs within 32 (HPET_MAX_TIMERS).
    the type of irqp->interrupt_count is u8.
    the git diff not display the relative lines below.
      hdp->hd_irq[hdp->hd_nirqs] = irq;
      hdp->hd_nirqs++;
    please check source code to get more information.
Signed-off-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/char/hpet.c

@@ -816,7 +816,7 @@ static unsigned long __hpet_calibrate(struct hpets *hpetp)
 
 static unsigned long hpet_calibrate(struct hpets *hpetp)
 {
-	unsigned long ret = -1;
+	unsigned long ret = ~0UL;
 	unsigned long tmp;
 
 	/*
@@ -1001,6 +1001,9 @@ static acpi_status hpet_resources(struct acpi_resource *res, void *data)
 		irqp = &res->data.extended_irq;
 
 		for (i = 0; i < irqp->interrupt_count; i++) {
+			if (hdp->hd_nirqs >= HPET_MAX_TIMERS)
+				break;
+
 			irq = acpi_register_gsi(NULL, irqp->interrupts[i],
 				      irqp->triggering, irqp->polarity);
 			if (irq < 0)