From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759487AbYGQBnS (ORCPT ); Wed, 16 Jul 2008 21:43:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753106AbYGQBnH (ORCPT ); Wed, 16 Jul 2008 21:43:07 -0400 Received: from mx1.redhat.com ([66.187.233.31]:56824 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752033AbYGQBnG (ORCPT ); Wed, 16 Jul 2008 21:43:06 -0400 Date: Wed, 16 Jul 2008 21:42:59 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@devserv.devel.redhat.com To: torvalds@linux-foundation.org cc: linux-kernel@vger.kernel.org Subject: [PATCH] Limit irq nesting Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi During examination of stack-overflows on sparc64, it was found that there is no limit for a number of nested IRQ handlers. Sparc64 is especially stack-hungry architecture, minimum frame size is 192 bytes and after 75 frames it overflows. If someone provides a legitimate reason for more than 2 nested handlers, you could increase the constant in the patch --- but there really should be some limit, so that many simultaneous interrupts can't blow the stack. Mikulas --- IRQs without IRQF_DISABLED could nest to arbitrary level. At worst this would mean having as many IRQ handlers stack frames, as there are interrupts registered --- enough to cause a stack overflow. This patch makes a limit to have at most two handlers on the stack. Signed-off-by: Mikulas Patocka --- include/linux/interrupt.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) Index: linux-2.6.26-rc8/include/linux/interrupt.h =================================================================== --- linux-2.6.26-rc8.orig/include/linux/interrupt.h 2008-06-25 03:58:20.000000000 +0200 +++ linux-2.6.26-rc8/include/linux/interrupt.h 2008-07-01 17:42:44.000000000 +0200 @@ -16,6 +16,11 @@ #include /* + * Max number of interrupt handlers on a stack. To prevent stack overflow. + */ +#define MAX_NESTED_INTERRUPTS 2 + +/* * These correspond to the IORESOURCE_IRQ_* defines in * linux/ioport.h to select the interrupt line behaviour. When * requesting an interrupt without specifying a IRQF_TRIGGER, the @@ -95,7 +100,7 @@ extern void devm_free_irq(struct device #ifdef CONFIG_LOCKDEP # define local_irq_enable_in_hardirq() do { } while (0) #else -# define local_irq_enable_in_hardirq() local_irq_enable() +# define local_irq_enable_in_hardirq() do { if (hardirq_count() < (MAX_NESTED_INTERRUPTS << HARDIRQ_SHIFT)) local_irq_enable(); } while (0) #endif extern void disable_irq_nosync(unsigned int irq);