[PATCH 4.9 19/28] genirq: Prevent use-after-free and work list corruption

[Greg Kroah-Hartman]

[ Upstream commit 59c39840f5abf4a71e1810a8da71aaccd6c17d26 ]

When irq_set_affinity_notifier() replaces the notifier, then the
reference count on the old notifier is dropped which causes it to be
freed. But nothing ensures that the old notifier is not longer queued
in the work list. If it is queued this results in a use after free and
possibly in work list corruption.

Ensure that the work is canceled before the reference is dropped.

Signed-off-by: Prasad Sodagudi <psodagud@xxxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: marc.zyngier@xxxxxxx
Link: https://lkml.kernel.org/r/1553439424-6529-1-git-send-email-psodagud@xxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 kernel/irq/manage.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index cf94460504bba..be7f489788e27 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -332,8 +332,10 @@ irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify)
 	desc->affinity_notify = notify;
 	raw_spin_unlock_irqrestore(&desc->lock, flags);
 
-	if (old_notify)
+	if (old_notify) {
+		cancel_work_sync(&old_notify->work);
 		kref_put(&old_notify->kref, old_notify->release);
+	}
 
 	return 0;
 }
-- 
2.20.1