linux-kernel - [39/59] pcmcia: avoid buffer overflow in pcmcia_setup_isa

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Date:	Tue, 24 Aug 2010 15:24:51 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Dominik Brodowski <linux@...inikbrodowski.net>,
	Christoph Fritz <chf.fritz@...glemail.com>
Subject: [39/59] pcmcia: avoid buffer overflow in pcmcia_setup_isa_irq

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Dominik Brodowski <linux@...inikbrodowski.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@...glemail.com>
Signed-off-by: Dominik Brodowski <linux@...inikbrodowski.net>
Signed-off-by: Christoph Fritz <chf.fritz@...glemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.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
@@ -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_dev
 		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;


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