| Date | Thu, 10 Feb 2011 23:36:03 -0000 | From | Thomas Gleixner <> | Subject | [patch 06/75] genirq: Plug race in report_bad_irq() |
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We cannot walk the action chain unlocked. Even if IRQ_INPROGRESS is set an action can be removed and we follow a null pointer. It's safe to take the lock there, because the code which removes the action will call synchronize_irq() which waits unlocked for IRQ_INPROGRESS going away.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> --- kernel/irq/spurious.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)
Index: linux-2.6-tip/kernel/irq/spurious.c =================================================================== --- linux-2.6-tip.orig/kernel/irq/spurious.c +++ linux-2.6-tip/kernel/irq/spurious.c @@ -139,15 +139,13 @@ static void poll_spurious_irqs(unsigned * * (The other 100-of-100,000 interrupts may have been a correctly * functioning device sharing an IRQ with the failing one) - * - * Called under desc->lock */ - static void __report_bad_irq(unsigned int irq, struct irq_desc *desc, irqreturn_t action_ret) { struct irqaction *action; + unsigned long flags; if (action_ret != IRQ_HANDLED && action_ret != IRQ_NONE) { printk(KERN_ERR "irq event %d: bogus return value %x\n", @@ -159,6 +157,13 @@ __report_bad_irq(unsigned int irq, struc dump_stack(); printk(KERN_ERR "handlers:\n"); + /* + * We need to take desc->lock here. note_interrupt() is called + * w/o desc->lock held, but IRQ_PROGRESS set. We might race + * with something else removing an action. It's ok to take + * desc->lock here. See synchronize_irq(). + */ + raw_spin_lock_irqsave(&desc->lock, flags); action = desc->action; while (action) { printk(KERN_ERR "[<%p>]", action->handler); @@ -167,6 +172,7 @@ __report_bad_irq(unsigned int irq, struc printk("\n"); action = action->next; } + raw_spin_unlock_irqrestore(&desc->lock, flags); } static void
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