Commit df81dfcf authored Mar 13, 2020 by Edward Cree Committed by Thomas Gleixner Mar 21, 2020

genirq: Fix reference leaks on irq affinity notifiers



The handling of notify->work did not properly maintain notify->kref in two
 cases:
1) where the work was already scheduled, another irq_set_affinity_locked()
   would get the ref and (no-op-ly) schedule the work.  Thus when
   irq_affinity_notify() ran, it would drop the original ref but not the
   additional one.
2) when cancelling the (old) work in irq_set_affinity_notifier(), if there
   was outstanding work a ref had been got for it but was never put.
Fix both by checking the return values of the work handling functions
 (schedule_work() for (1) and cancel_work_sync() for (2)) and put the
 extra ref if the return value indicates preexisting work.

Fixes: cd7eab44 ("genirq: Add IRQ affinity notifiers")
Fixes: 59c39840 ("genirq: Prevent use-after-free and work list corruption")
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ben Hutchings <ben@decadent.org.uk>
Link: https://lkml.kernel.org/r/24f5983f-2ab5-e83a-44ee-a45b5f9300f5@solarflare.com

parent 5ad0ec0b

kernel/irq/manage.c

+9 −2

Original line number	Diff line number	Diff line
		@@ -323,7 +323,11 @@ int irq_set_affinity_locked(struct irq_data data, const struct cpumask mask,

		if (desc->affinity_notify) {
		kref_get(&desc->affinity_notify->kref);
		schedule_work(&desc->affinity_notify->work);
		if (!schedule_work(&desc->affinity_notify->work)) {
		/* Work was already scheduled, drop our extra ref */
		kref_put(&desc->affinity_notify->kref,
		desc->affinity_notify->release);
		}
		}
		irqd_set(data, IRQD_AFFINITY_SET);

		@@ -423,7 +427,10 @@ irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify)
		raw_spin_unlock_irqrestore(&desc->lock, flags);

		if (old_notify) {
		cancel_work_sync(&old_notify->work);
		if (cancel_work_sync(&old_notify->work)) {
		/* Pending work had a ref, put that one too */
		kref_put(&old_notify->kref, old_notify->release);
		}
		kref_put(&old_notify->kref, old_notify->release);
		}

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