iwlwifi: fix use-after-free

If no firmware was present at all (or, presumably, all of the
firmware files failed to parse), we end up unbinding by calling
device_release_driver(), which calls remove(), which then in
iwlwifi calls iwl_drv_stop(), freeing the 'drv' struct. However
the new code I added will still erroneously access it after it
was freed.

Set 'failure=false' in this case to avoid the access, all data
was already freed anyway.

Cc: stable@vger.kernel.org
Reported-by: Stefan Agner <stefan@agner.ch>
Reported-by: Wolfgang Walter <linux@stwm.de>
Reported-by: Jason Self <jason@bluehome.net>
Reported-by: Dominik Behr <dominik@dominikbehr.com>
Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Fixes: ab07506b ("iwlwifi: fix leaks/bad data after failed firmware load")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220208114728.e6b514cf4c85.Iffb575ca2a623d7859b542c33b2a507d01554251@changeid

drivers/net/wireless/intel/iwlwifi/iwl-drv.c

@@ -1707,6 +1707,8 @@ static void iwl_req_fw_callback(const struct firmware *ucode_raw, void *context)
  out_unbind:
 	complete(&drv->request_firmware_complete);
 	device_release_driver(drv->trans->dev);
+	/* drv has just been freed by the release */
+	failure = false;
  free:
 	if (failure)
 		iwl_dealloc_ucode(drv);