nl80211: fix overflow in ssid_len

commit 57a27e1d6a3bb9ad4efeebd3a8c71156d6207536 upstream.

When one of the SSID's length passed in a scan or sched_scan request
is larger than 255, there will be an overflow in the u8 that is used
to store the length before checking.  This causes the check to fail
and we overrun the buffer when copying the SSID.

Fix this by checking the nl80211 attribute length before copying it to
the struct.

This is a follow up for the previous commit
208c72f4fe44fe09577e7975ba0e7fa0278f3d03, which didn't fix the problem
entirely.

Reported-by: Ido Yariv <ido@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index c901245e4ceb228afb06e61691a882d8b6cfd5f8..dbb6dde6b30506b003846e64667058c514d2f18d 100644 (file)
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -2995,11 +2995,11 @@ static int nl80211_trigger_scan(struct sk_buff *skb, struct genl_info *info)
        i = 0;
        if (info->attrs[NL80211_ATTR_SCAN_SSIDS]) {
                nla_for_each_nested(attr, info->attrs[NL80211_ATTR_SCAN_SSIDS], tmp) {
-                       request->ssids[i].ssid_len = nla_len(attr);
-                       if (request->ssids[i].ssid_len > IEEE80211_MAX_SSID_LEN) {
+                       if (nla_len(attr) > IEEE80211_MAX_SSID_LEN) {
                                err = -EINVAL;
                                goto out_free;
                        }
+                       request->ssids[i].ssid_len = nla_len(attr);
                        memcpy(request->ssids[i].ssid, nla_data(attr), nla_len(attr));
                        i++;
                }