mac80211: sanity check for null SSID

While associated we should never have empty SSID, but life can be full
of surprises, and is allways better to print a warning than crash.

Before memcpy() in ieee80211_probereq_get() check ssid_len instead of
ssid pointer, sice pointer it always passed by "ssidie + 2" expression
to send probe functions, so practically never can be NULL.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

2 files changed, 17 insertions, 4 deletions

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 93d484c8a0b8..12ca9820689a 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -1518,9 +1518,16 @@ static void ieee80211_mgd_probe_ap_send(struct ieee80211_sub_if_data *sdata)
                 ifmgd->nullfunc_failed = false;
                 ieee80211_send_nullfunc(sdata->local, sdata, 0);
         } else {
+                int ssid_len;
+
                 ssid = ieee80211_bss_get_ie(ifmgd->associated, WLAN_EID_SSID);
-                ieee80211_send_probe_req(sdata, dst, ssid + 2, ssid[1], NULL, 0,
-                                         (u32) -1, true, false);
+                if (WARN_ON_ONCE(ssid == NULL))
+                        ssid_len = 0;
+                else
+                        ssid_len = ssid[1];
+
+                ieee80211_send_probe_req(sdata, dst, ssid + 2, ssid_len, NULL,
+                                         0, (u32) -1, true, false);
         }
 
         ifmgd->probe_send_count++;
@@ -1596,6 +1603,7 @@ struct sk_buff *ieee80211_ap_probereq_get(struct ieee80211_hw *hw,
         struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
         struct sk_buff *skb;
         const u8 *ssid;
+        int ssid_len;
 
         if (WARN_ON(sdata->vif.type != NL80211_IFTYPE_STATION))
                 return NULL;
@@ -1606,8 +1614,13 @@ struct sk_buff *ieee80211_ap_probereq_get(struct ieee80211_hw *hw,
                 return NULL;
 
         ssid = ieee80211_bss_get_ie(ifmgd->associated, WLAN_EID_SSID);
+        if (WARN_ON_ONCE(ssid == NULL))
+                ssid_len = 0;
+        else
+                ssid_len = ssid[1];
+
         skb = ieee80211_build_probe_req(sdata, ifmgd->associated->bssid,
-                                        (u32) -1, ssid + 2, ssid[1],
+                                        (u32) -1, ssid + 2, ssid_len,
                                         NULL, 0, true);
 
         return skb;
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 14a01c81f959..e0b89780b472 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -2602,7 +2602,7 @@ struct sk_buff *ieee80211_probereq_get(struct ieee80211_hw *hw,
         pos = skb_put(skb, ie_ssid_len);
         *pos++ = WLAN_EID_SSID;
         *pos++ = ssid_len;
-        if (ssid)
+        if (ssid_len)
                 memcpy(pos, ssid, ssid_len);
         pos += ssid_len;