Messages in this thread Patch in this message | | | Subject | Re: [PATCH] genirq: fix reference leaks on irq affinity notifiers | From | Ben Hutchings <> | Date | Sun, 15 Mar 2020 20:29:16 +0000 |
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On Fri, 2020-03-13 at 20:33 +0000, Edward Cree wrote: > 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.
This makes sense, but...
> 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>
...since the pending work item holds a reference to the notification state, it's still not clear to me why or whether "genirq: Prevent use- after-free and work list corruption" was needed.
If it's reasonable to cancel_work_sync() when removing a notifier, I think we can remove the kref and call the release function directly.
Ben.
> --- > kernel/irq/manage.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c > index 7eee98c38f25..b3aa1db895e6 100644 > --- a/kernel/irq/manage.c > +++ b/kernel/irq/manage.c > @@ -323,7 +323,10 @@ 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 +426,9 @@ 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); > } > -- Ben Hutchings Humour is the best antidote to reality.
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