iwlwifi: mvm: guard against device removal in reprobe

If we get into a problem severe enough to attempt a reprobe,
we schedule a worker to do that. However, if the problem gets
more severe and the device is actually destroyed before this
worker has a chance to run, we use a free device. Bump up the
reference count of the device until the worker runs to avoid
this situation.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/iwlwifi.20210122144849.871f0892e4b2.I94819e11afd68d875f3e242b98bef724b8236f1e@changeid

drivers/net/wireless/intel/iwlwifi/mvm/ops.c

@@ -1209,6 +1209,7 @@ static void iwl_mvm_reprobe_wk(struct work_struct *wk)
 	reprobe = container_of(wk, struct iwl_mvm_reprobe, work);
 	if (device_reprobe(reprobe->dev))
 		dev_err(reprobe->dev, "reprobe failed!\n");
+	put_device(reprobe->dev);
 	kfree(reprobe);
 	module_put(THIS_MODULE);
 }
@@ -1259,7 +1260,7 @@ void iwl_mvm_nic_restart(struct iwl_mvm *mvm, bool fw_error)
 			module_put(THIS_MODULE);
 			return;
 		}
-		reprobe->dev = mvm->trans->dev;
+		reprobe->dev = get_device(mvm->trans->dev);
 		INIT_WORK(&reprobe->work, iwl_mvm_reprobe_wk);
 		schedule_work(&reprobe->work);
 	} else if (test_bit(IWL_MVM_STATUS_HW_RESTART_REQUESTED,