mwifiex: printk() overflow with 32-byte SSIDs

commit fcd2042e upstream.

SSIDs aren't guaranteed to be 0-terminated. Let's cap the max length
when we print them out.

This can be easily noticed by connecting to a network with a 32-octet
SSID:

[ 3903.502925] mwifiex_pcie 0000:01:00.0: info: trying to associate to
'0123456789abcdef0123456789abcdef <uninitialized mem>' bssid
xx:xx:xx:xx:xx:xx

Fixes: 5e6e3a92 ("wireless: mwifiex: initial commit for Marvell mwifiex driver")
Signed-off-by: Brian Norris <briannorris@chromium.org>
Acked-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/net/wireless/mwifiex/cfg80211.c

@@ -1734,8 +1734,9 @@ mwifiex_cfg80211_assoc(struct mwifiex_private *priv, size_t ssid_len,
 			is_scanning_required = 1;
 		} else {
 			dev_dbg(priv->adapter->dev,
-				"info: trying to associate to '%s' bssid %pM\n",
-				(char *) req_ssid.ssid, bss->bssid);
+				"info: trying to associate to '%.*s' bssid %pM\n",
+				req_ssid.ssid_len, (char *)req_ssid.ssid,
+				bss->bssid);
 			memcpy(&priv->cfg_bssid, bss->bssid, ETH_ALEN);
 			break;
 		}
@@ -1776,8 +1777,8 @@ mwifiex_cfg80211_connect(struct wiphy *wiphy, struct net_device *dev,
 		return -EINVAL;
 	}
 
-	wiphy_dbg(wiphy, "info: Trying to associate to %s and bssid %pM\n",
-		  (char *) sme->ssid, sme->bssid);
+	wiphy_dbg(wiphy, "info: Trying to associate to %.*s and bssid %pM\n",
+		  (int)sme->ssid_len, (char *)sme->ssid, sme->bssid);
 
 	ret = mwifiex_cfg80211_assoc(priv, sme->ssid_len, sme->ssid, sme->bssid,
 				     priv->bss_mode, sme->channel, sme, 0);
@@ -1900,8 +1901,8 @@ mwifiex_cfg80211_join_ibss(struct wiphy *wiphy, struct net_device *dev,
 		goto done;
 	}
 
-	wiphy_dbg(wiphy, "info: trying to join to %s and bssid %pM\n",
-		  (char *) params->ssid, params->bssid);
+	wiphy_dbg(wiphy, "info: trying to join to %.*s and bssid %pM\n",
+		  params->ssid_len, (char *)params->ssid, params->bssid);
 
 	mwifiex_set_ibss_params(priv, params);