[PATCH 1/2] mac80211: Reject malformed SSID elements

[Will Deacon]

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: <sta...@vger.kernel.org>
Cc: Johannes Berg <johan...@sipsolutions.net>
Cc: Kees Cook <keesc...@chromium.org>
Reported-by: Nicolas Waisman <n...@semmle.com>
Signed-off-by: Will Deacon <w...@kernel.org>
---
 net/mac80211/mlme.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 26a2f49208b6..54dd8849d1cc 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -2633,7 +2633,8 @@ 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];
@@ -5233,7 +5234,7 @@ 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;
-- 
2.23.0.581.g78d2f28ef7-goog