From: Will Deacon <will@kernel.org>
Date: Fri, 4 Oct 2019 10:51:31 +0100
Subject: mac80211: Reject malformed SSID elements
Git-commit: 4152561f5da3fca92af7179dd538ea89e248f9d0
Patch-mainline: 5.4-rc4
References: bnc#1151927 5.3.8

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: Jiri Slaby <jslaby@suse.cz>
---
 net/mac80211/mlme.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -2629,7 +2629,8 @@ struct sk_buff *ieee80211_ap_probereq_ge
 
 	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];
@@ -5227,7 +5228,7 @@ int ieee80211_mgd_assoc(struct ieee80211
 
 	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;