nl80211: take RCU read lock when calling ieee80211_bss_get_ie()

commit 7a94b8c2eee7083ddccd0515830f8c81a8e44b1a upstream.

As ieee80211_bss_get_ie() derefences an RCU to return ssid_ie, both
the call to this function and any operation on this variable need
protection by the RCU read lock.

Fixes: 44905265bc15 ("nl80211: don't expose wdev->ssid for most interfaces")
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 38657f3cbb3892b515db17438e31a764bac2fd3a..81addba0aa34a81aa6724eb8b55925c586739ebb 100644 (file)
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -2354,12 +2354,13 @@ static int nl80211_send_iface(struct sk_buff *msg, u32 portid, u32 seq, int flag
                const u8 *ssid_ie;
                if (!wdev->current_bss)
                        break;
+               rcu_read_lock();
                ssid_ie = ieee80211_bss_get_ie(&wdev->current_bss->pub,
                                               WLAN_EID_SSID);
-               if (!ssid_ie)
-                       break;
-               if (nla_put(msg, NL80211_ATTR_SSID, ssid_ie[1], ssid_ie + 2))
-                       goto nla_put_failure_locked;
+               if (ssid_ie &&
+                   nla_put(msg, NL80211_ATTR_SSID, ssid_ie[1], ssid_ie + 2))
+                       goto nla_put_failure_rcu_locked;
+               rcu_read_unlock();
                break;
                }
        default:
@@ -2370,6 +2371,8 @@ static int nl80211_send_iface(struct sk_buff *msg, u32 portid, u32 seq, int flag
 
        return genlmsg_end(msg, hdr);
 
+ nla_put_failure_rcu_locked:
+       rcu_read_unlock();
  nla_put_failure_locked:
        wdev_unlock(wdev);
  nla_put_failure: