linux-kernel - [PATCH 4.14 095/119] mac80211: Reject malformed SSID elements

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Date:   Sun, 27 Oct 2019 22:01:12 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        Nicolas Waisman <nico@...mle.com>,
        Will Deacon <will@...nel.org>,
        Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH 4.14 095/119] mac80211: Reject malformed SSID elements

From: Will Deacon <will@...nel.org>

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@...r.kernel.org>
Cc: Kees Cook <keescook@...omium.org>
Reported-by: Nicolas Waisman <nico@...mle.com>
Signed-off-by: Will Deacon <will@...nel.org>
Link: https://lore.kernel.org/r/20191004095132.15777-1-will@kernel.org
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/mac80211/mlme.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -2430,7 +2430,8 @@ 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];
@@ -4756,7 +4757,7 @@ 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;