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: cd7eab44e994 ("genirq: Add IRQ affinity notifiers")
Fixes: 59c39840f5ab ("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

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 7eee98c38f25ca20047ed75c268fae4550949bdd..fe40c658f86f851bb175ff1c374e7c808007b04f 100644 (file)
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -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);
        }