[PATCH 5.10 067/126] PM: runtime: Fix race getting/putting suppliers at probe

Greg Kroah-Hartman
2021-04-05T09:11:46Z

From: Adrian Hunter <adrian.hunter@intel.com>

commit 9dfacc54a8661bc8be6e08cffee59596ec59f263 upstream.

pm_runtime_put_suppliers() must not decrement rpm_active unless the
consumer is suspended. That is because, otherwise, it could suspend
suppliers for an active consumer.

That can happen as follows:

static int driver_probe_device(struct device_driver *drv, struct device *dev)
{
int ret = 0;

if (!device_is_registered(dev))
return -ENODEV;

dev->can_match = true;
pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
drv->bus->name, __func__, dev_name(dev), drv->name);

pm_runtime_get_suppliers(dev);
if (dev->parent)
pm_runtime_get_sync(dev->parent);

At this point, dev can runtime suspend so rpm_put_suppliers() can run,
rpm_active becomes 1 (the lowest value).

pm_runtime_barrier(dev);
if (initcall_debug)
ret = really_probe_debug(dev, drv);
else
ret = really_probe(dev, drv);

Probe callback can have runtime resumed dev, and then runtime put
so dev is awaiting autosuspend, but rpm_active is 2.

pm_request_idle(dev);

if (dev->parent)
pm_runtime_put(dev->parent);

pm_runtime_put_suppliers(dev);

Now pm_runtime_put_suppliers() will put the supplier
i.e. rpm_active 2 -> 1, but consumer can still be active.

return ret;
}

Fix by checking the runtime status. For any status other than
RPM_SUSPENDED, rpm_active can be considered to be "owned" by
rpm_[get/put]_suppliers() and pm_runtime_put_suppliers() need do nothing.

Reported-by: Asutosh Das <asutoshd@codeaurora.org>
Fixes: 4c06c4e6cf63 ("driver core: Fix possible supplier PM-usage counter imbalance")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: 5.1+ <stable@vger.kernel.org> # 5.1+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/base/power/runtime.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -1704,6 +1704,8 @@ void pm_runtime_get_suppliers(struct dev
void pm_runtime_put_suppliers(struct device *dev)
{
struct device_link *link;
+ unsigned long flags;
+ bool put;
int idx;

idx = device_links_read_lock();
@@ -1712,7 +1714,11 @@ void pm_runtime_put_suppliers(struct dev
device_links_read_lock_held())
if (link->supplier_preactivated) {
link->supplier_preactivated = false;
- if (refcount_dec_not_one(&link->rpm_active))
+ spin_lock_irqsave(&dev->power.lock, flags);
+ put = pm_runtime_status_suspended(dev) &&
+ refcount_dec_not_one(&link->rpm_active);
+ spin_unlock_irqrestore(&dev->power.lock, flags);
+ if (put)
pm_runtime_put(link->supplier);
}