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Date: Fri, 05 Feb 2010 14:44:57 -0800
From: Yinghai Lu <yinghai@...nel.org>
To: Brandon Philips <bphilips@...e.de>
CC: Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Suresh Siddha <suresh.b.siddha@...el.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: keep chip_data in create_irq_nr and destroy_irq
On 02/05/2010 01:09 PM, Brandon Philips wrote:
> 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 <bphilips@...e.de>
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> Signed-off-by: Brandon Phiilps <bphilips@...e.de>
> Cc: stable@...nel.org
>
> ---
> arch/x86/kernel/apic/io_apic.c | 14 +++--------
> include/linux/irq.h | 2 +
> kernel/irq/chip.c | 52 +++++++++++++++++++++++++++++++++--------
> 3 files changed, 49 insertions(+), 19 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;
> }
>
> @@ -3260,10 +3257,7 @@ void destroy_irq(unsigned int irq)
>
> /* 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);
> 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);
> +extern void dynamic_irq_init_keep_chip_data(unsigned int irq);
> extern void dynamic_irq_cleanup(unsigned int irq);
> +extern 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_init_x(irq, false);
should be dynamic_irq_cleanup_x here.
> +}
> +
> +/**
> + * 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_init_x(irq, true);
should be dynamic_irq_cleanup_x
> +}
> +
>
> /**
> * set_irq_chip - set the irq chip for an irq
YH
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