[PATCH net v2 1/2] net: pse-pd: stop async event sources before freeing PI data in unregister

[Carlo Szelinsky <github@szelinsky.de>]

pse_controller_unregister() frees resources that its own asynchronous
event sources are still using:

 * The PI array (pcdev->pi) is freed by pse_release_pis() while the
   threaded IRQ handler pse_isr() can still be running. pse_isr() walks
   pcdev->pi[] (via pse_set_config_isr() and
   regulator_notifier_call_chain() on pcdev->pi[i].rdev), so an interrupt
   arriving before disable_irq() dereferences freed memory.

 * pse_flush_pw_ds() runs before disable_irq() and drops the power domain
   references, which can free pw_d->supply via __pse_pw_d_release().
   A concurrent interrupt reaches that supply through
   _pse_pi_disable() -> pse_pw_d_retry_power_delivery() ->
   regulator_request_power_budget(pw_d->supply), another use-after-free.

 * cancel_work_sync(&pcdev->ntf_work) runs after pse_release_pis(), but
   the notification worker reaches pcdev->pi too: pse_send_ntf_worker()
   -> pse_control_put() -> __pse_control_release() dereferences
   psec->pcdev->pi[psec->id].admin_state_enabled. Draining the worker
   after the PI array is freed is therefore also a use-after-free.

Reorder teardown so every asynchronous accessor is stopped first:
disable the IRQ, drain the notification worker, and only then flush the
power domains and release the PI array.

Fixes: ffef61d6d273 ("net: pse-pd: Add support for budget evaluation strategies")
Signed-off-by: Carlo Szelinsky <github@szelinsky.de>
---
 drivers/net/pse-pd/pse_core.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/pse-pd/pse_core.c b/drivers/net/pse-pd/pse_core.c
index a5e6d7b26b9f..6045b6c399c2 100644
--- a/drivers/net/pse-pd/pse_core.c
+++ b/drivers/net/pse-pd/pse_core.c
@@ -1114,11 +1114,15 @@ EXPORT_SYMBOL_GPL(pse_controller_register);
  */
 void pse_controller_unregister(struct pse_controller_dev *pcdev)
 {
-	pse_flush_pw_ds(pcdev);
-	pse_release_pis(pcdev);
+	/* Stop the IRQ and notification worker before freeing what they
+	 * reach: both touch pcdev->pi, and the IRQ also uses pw_d->supply
+	 * that pse_flush_pw_ds() drops.
+	 */
 	if (pcdev->irq)
 		disable_irq(pcdev->irq);
 	cancel_work_sync(&pcdev->ntf_work);
+	pse_flush_pw_ds(pcdev);
+	pse_release_pis(pcdev);
 	kfifo_free(&pcdev->ntf_fifo);
 	mutex_lock(&pse_list_mutex);
 	list_del(&pcdev->list);
-- 
2.43.0