[PATCH 4.4 031/124] mwifiex: handle race during mwifiex_usb_disconnect

From: Greg Kroah-Hartman
Date: Sat Aug 04 2018 - 05:09:52 EST


4.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Ganapathi Bhat <gbhat@xxxxxxxxxxx>

[ Upstream commit b817047ae70c0bd67b677b65d0d69d72cd6e9728 ]

Race condition is observed during rmmod of mwifiex_usb:

1. The rmmod thread will call mwifiex_usb_disconnect(), download
SHUTDOWN command and do wait_event_interruptible_timeout(),
waiting for response.

2. The main thread will handle the response and will do a
wake_up_interruptible(), unblocking rmmod thread.

3. On getting unblocked, rmmod thread will make rx_cmd.urb = NULL in
mwifiex_usb_free().

4. The main thread will try to resubmit rx_cmd.urb in
mwifiex_usb_submit_rx_urb(), which is NULL.

To fix, wait for main thread to complete before calling
mwifiex_usb_free().

Signed-off-by: Ganapathi Bhat <gbhat@xxxxxxxxxxx>
Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/wireless/mwifiex/usb.c | 3 +++
1 file changed, 3 insertions(+)

--- a/drivers/net/wireless/mwifiex/usb.c
+++ b/drivers/net/wireless/mwifiex/usb.c
@@ -624,6 +624,9 @@ static void mwifiex_usb_disconnect(struc
MWIFIEX_FUNC_SHUTDOWN);
}

+ if (adapter->workqueue)
+ flush_workqueue(adapter->workqueue);
+
mwifiex_usb_free(card);

mwifiex_dbg(adapter, FATAL,