mwifiex: fix use-after-free in beacon_ie processing

beacon_ie buffer is allocated in mwifiex_fill_new_bss_desc()
and the buffer pointer is saved in bss_desc->beacon_buf.
beacon_ie is freed before the function returns. However,
bss_desc->beacon_buf is still being accessed afterwards.

Fix it by freeing beacon_ie (bss_desc->beacon_buf) in
caller's scope.

Reviewed-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/mwifiex/scan.c b/drivers/net/wireless/mwifiex/scan.c
index e7f6dea..37b24e8 100644
--- a/drivers/net/wireless/mwifiex/scan.c
+++ b/drivers/net/wireless/mwifiex/scan.c
@@ -1533,10 +1533,18 @@
 	/* Make a copy of current BSSID descriptor */
 	memcpy(&priv->curr_bss_params.bss_descriptor, bss_desc,
 	       sizeof(priv->curr_bss_params.bss_descriptor));
+
+	/* The contents of beacon_ie will be copied to its own buffer
+	 * in mwifiex_save_curr_bcn()
+	 */
 	mwifiex_save_curr_bcn(priv);
 	spin_unlock_irqrestore(&priv->curr_bcn_buf_lock, flags);
 
 done:
+	/* beacon_ie buffer was allocated in function
+	 * mwifiex_fill_new_bss_desc(). Free it now.
+	 */
+	kfree(bss_desc->beacon_buf);
 	kfree(bss_desc);
 	return 0;
 }