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Subject[patch 06/75] genirq: Plug race in report_bad_irq()
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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