mwifiex: fix unbalanced locking in mwifiex_process_country_ie()

BugLink: https://bugs.launchpad.net/bugs/1864775

commit 65b1aae0 upstream.

We called rcu_read_lock(), so we need to call rcu_read_unlock() before
we return.

Fixes: 3d94a4a8 ("mwifiex: fix possible heap overflow in mwifiex_process_country_ie()")
Cc: stable@vger.kernel.org
Cc: huangwen <huangwenabc@gmail.com>
Cc: Ganapathi Bhat <ganapathi.bhat@nxp.com>
Signed-off-by: Brian Norris <briannorris@chromium.org>
Acked-by: Ganapathi Bhat <ganapathi.bhat@nxp.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/net/wireless/mwifiex/sta_ioctl.c

@@ -234,6 +234,7 @@ static int mwifiex_process_country_ie(struct mwifiex_private *priv,
 
 	if (country_ie_len >
 	    (IEEE80211_COUNTRY_STRING_LEN + MWIFIEX_MAX_TRIPLET_802_11D)) {
+		rcu_read_unlock();
 		mwifiex_dbg(priv->adapter, ERROR,
 			    "11D: country_ie_len overflow!, deauth AP\n");
 		return -EINVAL;