regulatory: add NUL to alpha2

commit a5fe8e7695dc3f547e955ad2b662e3e72969e506 upstream.

alpha2 is defined as 2-chars array, but is used in multiple
places as string (e.g. with nla_put_string calls), which
might leak kernel data.

Solve it by simply adding an extra char for the NULL
terminator, making such operations safe.

Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@huawei.com>
diff --git a/include/net/regulatory.h b/include/net/regulatory.h
index a5f7993..8d64abf 100644
--- a/include/net/regulatory.h
+++ b/include/net/regulatory.h
@@ -97,7 +97,7 @@
 
 struct ieee80211_regdomain {
 	u32 n_reg_rules;
-	char alpha2[2];
+	char alpha2[3];
 	u8 dfs_region;
 	struct ieee80211_reg_rule reg_rules[];
 };