[PATCH 5.5 121/170] genirq: Fix reference leaks on irq affinity notifiers

[Greg Kroah-Hartman]

From: Edward Cree <ecree@xxxxxxxxxxxxxx>

commit df81dfcfd6991d547653d46c051bac195cd182c1 upstream.

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@xxxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/24f5983f-2ab5-e83a-44ee-a45b5f9300f5@xxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 kernel/irq/manage.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -284,7 +284,11 @@ int irq_set_affinity_locked(struct irq_d
 
 	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);
 
@@ -384,7 +388,10 @@ irq_set_affinity_notifier(unsigned int i
 	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);
 	}