[07/67] pcmcia: avoid buffer overflow in pcmcia_setup_isa_irq

Greg KH
2010-08-12T00:07:58Z

From: Dominik Brodowski <linux@dominikbrodowski.net>

commit 127c03cdbad9bd5af5d7f33bd31a1015a90cb77f 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 | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/pcmcia/pcmcia_resource.c
+++ b/drivers/pcmcia/pcmcia_resource.c
@@ -651,7 +651,7 @@ EXPORT_SYMBOL(__pcmcia_request_exclusive
#ifdef CONFIG_PCMCIA_PROBE

/* 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];

static irqreturn_t test_action(int cpl, void *dev_id)
{
@@ -674,6 +674,9 @@ static int pcmcia_setup_isa_irq(struct p
for (try = 0; try < 64; try++) {
irq = try % 32;

+ if (irq > NR_IRQS)
+ continue;
+
/* marked as available by driver, not blocked by userspace? */
if (!((mask >> irq) & 1))
continue;