mac80211_hwsim: fix possible memory leak in hwsim_new_radio_nl()

CVE-2018-8087

'hwname' is malloced in hwsim_new_radio_nl() and should be freed
before leaving from the error handling cases, otherwise it will cause
memory leak.

Fixes: ff4dd73d ("mac80211_hwsim: check HWSIM_ATTR_RADIO_NAME length")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
(cherry-picked from 0ddcff49)
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Acked-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Acked-by: Andy Whitcroft <andy.whitcroft@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/net/wireless/mac80211_hwsim.c

@@ -2925,8 +2925,10 @@ static int hwsim_new_radio_nl(struct sk_buff *msg, struct genl_info *info)
 	if (info->attrs[HWSIM_ATTR_REG_CUSTOM_REG]) {
 		u32 idx = nla_get_u32(info->attrs[HWSIM_ATTR_REG_CUSTOM_REG]);
 
-		if (idx >= ARRAY_SIZE(hwsim_world_regdom_custom))
+		if (idx >= ARRAY_SIZE(hwsim_world_regdom_custom)) {
+			kfree(hwname);
 			return -EINVAL;
+		}
 		param.regd = hwsim_world_regdom_custom[idx];
 	}