From ced5b697a76d325e7a7ac7d382dbbb632c765093 Mon Sep 17 00:00:00 2001 From: Brandon Phiilps Date: Wed, 10 Feb 2010 01:20:06 -0800 Subject: [PATCH] x86: Avoid race condition in pci_enable_msix() Keep chip_data in create_irq_nr and destroy_irq. 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 LKML-Reference: <1265793639-15071-3-git-send-email-yinghai@kernel.org> Signed-off-by: Brandon Phililps Cc: stable@kernel.org Signed-off-by: H. Peter Anvin --- arch/x86/kernel/apic/io_apic.c | 18 ++++-------- include/linux/irq.h | 2 ++ kernel/irq/chip.c | 52 ++++++++++++++++++++++++++++------ 3 files changed, 50 insertions(+), 22 deletions(-) diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c index 53243ca7816d..c86591b906fa 100644 --- a/arch/x86/kernel/apic/io_apic.c +++ b/arch/x86/kernel/apic/io_apic.c @@ -3228,12 +3228,9 @@ unsigned int create_irq_nr(unsigned int irq_want, int node) } 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; } @@ -3256,17 +3253,12 @@ 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); + cfg = irq_to_desc(irq)->chip_data; __clear_irq_vector(irq, cfg); spin_unlock_irqrestore(&vector_lock, flags); } diff --git a/include/linux/irq.h b/include/linux/irq.h index 451481c082b5..4d9b26e044bc 100644 --- a/include/linux/irq.h +++ b/include/linux/irq.h @@ -400,7 +400,9 @@ static inline int irq_has_action(unsigned int irq) /* 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); diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c index ecc3fa28f666..d70394f12ee9 100644 --- a/kernel/irq/chip.c +++ b/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 irq) } 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 irq) 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 -- 2.20.1