[PATCH 2/2] cfg80211: wext: Reject malformed SSID elements

[Will Deacon <will@kernel.org>]

Ensure the SSID element is bounds-checked prior to invoking memcpy()
with its length field.

Cc: <stable@vger.kernel.org>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Kees Cook <keescook@chromium.org>
Reported-by: Nicolas Waisman <nico@semmle.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
 net/wireless/wext-sme.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/wireless/wext-sme.c b/net/wireless/wext-sme.c
index c67d7a82ab13..3fd2cc7fc36a 100644
--- a/net/wireless/wext-sme.c
+++ b/net/wireless/wext-sme.c
@@ -201,6 +201,7 @@ int cfg80211_mgd_wext_giwessid(struct net_device *dev,
 			       struct iw_request_info *info,
 			       struct iw_point *data, char *ssid)
 {
+	int ret = 0;
 	struct wireless_dev *wdev = dev->ieee80211_ptr;
 
 	/* call only for station! */
@@ -219,7 +220,10 @@ int cfg80211_mgd_wext_giwessid(struct net_device *dev,
 		if (ie) {
 			data->flags = 1;
 			data->length = ie[1];
-			memcpy(ssid, ie + 2, data->length);
+			if (data->length > IW_ESSID_MAX_SIZE)
+				ret = -EINVAL;
+			else
+				memcpy(ssid, ie + 2, data->length);
 		}
 		rcu_read_unlock();
 	} else if (wdev->wext.connect.ssid && wdev->wext.connect.ssid_len) {
@@ -229,7 +233,7 @@ int cfg80211_mgd_wext_giwessid(struct net_device *dev,
 	}
 	wdev_unlock(wdev);
 
-	return 0;
+	return ret;
 }
 
 int cfg80211_mgd_wext_siwap(struct net_device *dev,
-- 
2.23.0.581.g78d2f28ef7-goog