Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752350Ab0BFGnd (ORCPT ); Sat, 6 Feb 2010 01:43:33 -0500 Received: from cantor2.suse.de ([195.135.220.15]:43775 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751992Ab0BFGnb (ORCPT ); Sat, 6 Feb 2010 01:43:31 -0500 Date: Fri, 5 Feb 2010 22:42:47 -0800 From: Brandon Philips To: Yinghai Lu Cc: Ingo Molnar , "H. Peter Anvin" , Thomas Gleixner , Suresh Siddha , linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] x86: keep chip_data in create_irq_nr and destroy_irq Message-ID: <20100206064247.GB15556@jenkins.home.ifup.org> References: <20100203033109.GA17985@jenkins.home.ifup.org> <4B694DEF.70301@kernel.org> <20100203174216.GB17985@jenkins.home.ifup.org> <4B6BDAC0.3090900@kernel.org> <20100205210926.GE4930@jenkins.home.ifup.org> <4B6C9F69.4040605@kernel.org> <20100205225535.GF4930@jenkins.home.ifup.org> <4B6CB26C.405@kernel.org> <20100206001832.GG4930@jenkins.home.ifup.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100206001832.GG4930@jenkins.home.ifup.org> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6954 Lines: 218 Version 3: Forgot to refresh patch so destroy_irq() had uninitialized cfg as param to __clear_irq_vector(). Fixed now. When two drivers are setting up MSI-X at the same time via pci_enable_msix() there is a race. See this dmesg excerpt: [ 85.170610] ixgbe 0000:02:00.1: irq 97 for MSI/MSI-X [ 85.170611] alloc irq_desc for 99 on node -1 [ 85.170613] igb 0000:08:00.1: irq 98 for MSI/MSI-X [ 85.170614] alloc kstat_irqs on node -1 [ 85.170616] alloc irq_2_iommu on node -1 [ 85.170617] alloc irq_desc for 100 on node -1 [ 85.170619] alloc kstat_irqs on node -1 [ 85.170621] alloc irq_2_iommu on node -1 [ 85.170625] ixgbe 0000:02:00.1: irq 99 for MSI/MSI-X [ 85.170626] alloc irq_desc for 101 on node -1 [ 85.170628] igb 0000:08:00.1: irq 100 for MSI/MSI-X [ 85.170630] alloc kstat_irqs on node -1 [ 85.170631] alloc irq_2_iommu on node -1 [ 85.170635] alloc irq_desc for 102 on node -1 [ 85.170636] alloc kstat_irqs on node -1 [ 85.170639] alloc irq_2_iommu on node -1 [ 85.170646] BUG: unable to handle kernel NULL pointer dereference at 0000000000000088 As you can see igb and ixgbe are both alternating on create_irq_nr() via pci_enable_msix() in their probe function. ixgbe: While looping through irq_desc_ptrs[] via create_irq_nr() ixgbe choses irq_desc_ptrs[102] and exits the loop, drops vector_lock and calls dynamic_irq_init. Then it sets irq_desc_ptrs[102]->chip_data = NULL via dynamic_irq_init(). igb: Grabs the vector_lock now and starts looping over irq_desc_ptrs[] via create_irq_nr(). It gets to irq_desc_ptrs[102] and does this: cfg_new = irq_desc_ptrs[102]->chip_data; if (cfg_new->vector != 0) continue; This hits the NULL deref. Another possible race exists via pci_disable_msix() in a driver or in the number of error paths that call free_msi_irqs(): destroy_irq() dynamic_irq_cleanup() which sets desc->chip_data = NULL ...race window... desc->chip_data = cfg; Remove the save and restore code for cfg in create_irq_nr() and destroy_irq() and take the desc->lock when checking the irq_cfg. Reported-and-analyzed-by: Brandon Philips Signed-off-by: Yinghai Lu Signed-off-by: Brandon Phiilps Cc: stable@kernel.org --- arch/x86/kernel/apic/io_apic.c | 17 +++---------- include/linux/irq.h | 2 + kernel/irq/chip.c | 52 +++++++++++++++++++++++++++++++++-------- 3 files changed, 50 insertions(+), 21 deletions(-) Index: linux-2.6/arch/x86/kernel/apic/io_apic.c =================================================================== --- linux-2.6.orig/arch/x86/kernel/apic/io_apic.c +++ linux-2.6/arch/x86/kernel/apic/io_apic.c @@ -3228,12 +3228,9 @@ unsigned int create_irq_nr(unsigned int } spin_unlock_irqrestore(&vector_lock, flags); - if (irq > 0) { - dynamic_irq_init(irq); - /* restore it, in case dynamic_irq_init clear it */ - if (desc_new) - desc_new->chip_data = cfg_new; - } + if (irq > 0) + dynamic_irq_init_keep_chip_data(irq); + return irq; } @@ -3255,19 +3252,15 @@ int create_irq(void) void destroy_irq(unsigned int irq) { unsigned long flags; - struct irq_cfg *cfg; struct irq_desc *desc; /* store it, in case dynamic_irq_cleanup clear it */ desc = irq_to_desc(irq); - cfg = desc->chip_data; - dynamic_irq_cleanup(irq); - /* connect back irq_cfg */ - desc->chip_data = cfg; + dynamic_irq_cleanup_keep_chip_data(irq); free_irte(irq); spin_lock_irqsave(&vector_lock, flags); - __clear_irq_vector(irq, cfg); + __clear_irq_vector(irq, desc->chip_data); spin_unlock_irqrestore(&vector_lock, flags); } Index: linux-2.6/include/linux/irq.h =================================================================== --- linux-2.6.orig/include/linux/irq.h +++ linux-2.6/include/linux/irq.h @@ -400,7 +400,9 @@ static inline int irq_has_action(unsigne /* Dynamic irq helper functions */ extern void dynamic_irq_init(unsigned int irq); +void dynamic_irq_init_keep_chip_data(unsigned int irq); extern void dynamic_irq_cleanup(unsigned int irq); +void dynamic_irq_cleanup_keep_chip_data(unsigned int irq); /* Set/get chip/data for an IRQ: */ extern int set_irq_chip(unsigned int irq, struct irq_chip *chip); Index: linux-2.6/kernel/irq/chip.c =================================================================== --- linux-2.6.orig/kernel/irq/chip.c +++ linux-2.6/kernel/irq/chip.c @@ -18,11 +18,7 @@ #include "internals.h" -/** - * dynamic_irq_init - initialize a dynamically allocated irq - * @irq: irq number to initialize - */ -void dynamic_irq_init(unsigned int irq) +static void dynamic_irq_init_x(unsigned int irq, bool keep_chip_data) { struct irq_desc *desc; unsigned long flags; @@ -41,7 +37,8 @@ void dynamic_irq_init(unsigned int irq) desc->depth = 1; desc->msi_desc = NULL; desc->handler_data = NULL; - desc->chip_data = NULL; + if (!keep_chip_data) + desc->chip_data = NULL; desc->action = NULL; desc->irq_count = 0; desc->irqs_unhandled = 0; @@ -55,10 +52,26 @@ void dynamic_irq_init(unsigned int irq) } /** - * dynamic_irq_cleanup - cleanup a dynamically allocated irq + * dynamic_irq_init - initialize a dynamically allocated irq * @irq: irq number to initialize */ -void dynamic_irq_cleanup(unsigned int irq) +void dynamic_irq_init(unsigned int irq) +{ + dynamic_irq_init_x(irq, false); +} + +/** + * dynamic_irq_init_keep_chip_data - initialize a dynamically allocated irq + * @irq: irq number to initialize + * + * does not set irq_to_desc(irq)->chip_data to NULL + */ +void dynamic_irq_init_keep_chip_data(unsigned int irq) +{ + dynamic_irq_init_x(irq, true); +} + +static void dynamic_irq_cleanup_x(unsigned int irq, bool keep_chip_data) { struct irq_desc *desc = irq_to_desc(irq); unsigned long flags; @@ -77,7 +90,8 @@ void dynamic_irq_cleanup(unsigned int ir } desc->msi_desc = NULL; desc->handler_data = NULL; - desc->chip_data = NULL; + if (!keep_chip_data) + desc->chip_data = NULL; desc->handle_irq = handle_bad_irq; desc->chip = &no_irq_chip; desc->name = NULL; @@ -85,6 +99,26 @@ void dynamic_irq_cleanup(unsigned int ir raw_spin_unlock_irqrestore(&desc->lock, flags); } +/** + * dynamic_irq_cleanup - cleanup a dynamically allocated irq + * @irq: irq number to initialize + */ +void dynamic_irq_cleanup(unsigned int irq) +{ + dynamic_irq_cleanup_x(irq, false); +} + +/** + * dynamic_irq_cleanup_keep_chip_data - cleanup a dynamically allocated irq + * @irq: irq number to initialize + * + * does not set irq_to_desc(irq)->chip_data to NULL + */ +void dynamic_irq_cleanup_keep_chip_data(unsigned int irq) +{ + dynamic_irq_cleanup_x(irq, true); +} + /** * set_irq_chip - set the irq chip for an irq -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/