mac80211: Reject malformed SSID elements

BugLink: https://bugs.launchpad.net/bugs/1851876
commit 4152561f5da3fca92af7179dd538ea89e248f9d0 upstream.

Although this shouldn't occur in practice, it's a good idea to bounds
check the length field of the SSID element prior to using it for things
like allocations or memcpy operations.

Cc: <stable@vger.kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Reported-by: Nicolas Waisman <nico@semmle.com>
Signed-off-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20191004095132.15777-1-will@kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index c8e9a6415aaf4bb1c155e5a5db9d799af5e04be8..477f8f385654444703ff6a30dfe226dfd449b842 100644 (file)
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -2417,7 +2417,8 @@ struct sk_buff *ieee80211_ap_probereq_get(struct ieee80211_hw *hw,
 
        rcu_read_lock();
        ssid = ieee80211_bss_get_ie(cbss, WLAN_EID_SSID);
-       if (WARN_ON_ONCE(ssid == NULL))
+       if (WARN_ONCE(!ssid || ssid[1] > IEEE80211_MAX_SSID_LEN,
+                     "invalid SSID element (len=%d)", ssid ? ssid[1] : -1))
                ssid_len = 0;
        else
                ssid_len = ssid[1];
@@ -4739,7 +4740,7 @@ int ieee80211_mgd_assoc(struct ieee80211_sub_if_data *sdata,
 
        rcu_read_lock();
        ssidie = ieee80211_bss_get_ie(req->bss, WLAN_EID_SSID);
-       if (!ssidie) {
+       if (!ssidie || ssidie[1] > sizeof(assoc_data->ssid)) {
                rcu_read_unlock();
                kfree(assoc_data);
                return -EINVAL;