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Subject[tip: irq/urgent] genirq: Fix reference leaks on irq affinity notifiers
The following commit has been merged into the irq/urgent branch of tip:

Commit-ID: df81dfcfd6991d547653d46c051bac195cd182c1
Gitweb: https://git.kernel.org/tip/df81dfcfd6991d547653d46c051bac195cd182c1
Author: Edward Cree <ecree@solarflare.com>
AuthorDate: Fri, 13 Mar 2020 20:33:07
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Sat, 21 Mar 2020 17:32:46 +01:00

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

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

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 7eee98c..fe40c65 100644
--- 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);
}

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