mwifiex: fix kernel crash after shutdown command timeout

We observed a SHUTDOWN command timeout during reboot stress test due to
a corner case firmware bug. It can lead to either a use-after-free +
OOPS (on either the adapter structure, or the 'card' structure) or an
abort (where, e.g., the PCI device is "disabled" before we're done
dumping the FW).

We can avoid this by canceling/flushing the FW dump work:

(a) after we've terminated all other work queues (e.g., for processing
    commands which could time out)
(b) after we've disabled all interrupts (which could also queue more
    work for us)
(c) after we've unregistered the netdev and wiphy structures (and
    implicitly, and debugfs entries which could manually trigger FW dumps)
(d) before we've actually disabled the device (e.g.,
    pci_device_disable())

Altogether, this means no card->work will be scheduled if we sync at
a point that satisfies the above. This can be done at the beginning of
the .cleanup_if() callback.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/marvell/mwifiex/pcie.c

@@ -294,8 +294,6 @@ static void mwifiex_pcie_remove(struct pci_dev *pdev)
 	if (!adapter || !adapter->priv_num)
 		return;
 
-	cancel_work_sync(&card->work);
-
 	reg = card->pcie.reg;
 	if (reg)
 		ret = mwifiex_read_reg(adapter, reg->fw_status, &fw_status);
@@ -2854,6 +2852,8 @@ static void mwifiex_cleanup_pcie(struct mwifiex_adapter *adapter)
 	int ret;
 	u32 fw_status;
 
+	cancel_work_sync(&card->work);
+
 	ret = mwifiex_read_reg(adapter, reg->fw_status, &fw_status);
 	if (fw_status == FIRMWARE_READY_PCIE) {
 		mwifiex_dbg(adapter, INFO,

drivers/net/wireless/marvell/mwifiex/sdio.c

@@ -387,8 +387,6 @@ mwifiex_sdio_remove(struct sdio_func *func)
 	if (!adapter || !adapter->priv_num)
 		return;
 
-	cancel_work_sync(&card->work);
-
 	mwifiex_dbg(adapter, INFO, "info: SDIO func num=%d\n", func->num);
 
 	ret = mwifiex_sdio_read_fw_status(adapter, &firmware_stat);
@@ -2158,6 +2156,8 @@ static void mwifiex_cleanup_sdio(struct mwifiex_adapter *adapter)
 {
 	struct sdio_mmc_card *card = adapter->card;
 
+	cancel_work_sync(&card->work);
+
 	kfree(card->mp_regs);
 	kfree(card->mpa_rx.skb_arr);
 	kfree(card->mpa_rx.len_arr);