[PATCH 5.17 197/219] nl80211: correctly check NL80211_ATTR_REG_ALPHA2 size

[Greg Kroah-Hartman]

From: Johannes Berg <johannes.berg@xxxxxxxxx>

commit 6624bb34b4eb19f715db9908cca00122748765d7 upstream.

We need this to be at least two bytes, so we can access
alpha2[0] and alpha2[1]. It may be three in case some
userspace used NUL-termination since it was NLA_STRING
(and we also push it out with NUL-termination).

Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Lee Jones <lee.jones@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20220411114201.fd4a31f06541.Ie7ff4be2cf348d8cc28ed0d626fc54becf7ea799@changeid
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/wireless/nl80211.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -519,7 +519,8 @@ static const struct nla_policy nl80211_p
 				   .len = IEEE80211_MAX_MESH_ID_LEN },
 	[NL80211_ATTR_MPATH_NEXT_HOP] = NLA_POLICY_ETH_ADDR_COMPAT,
 
-	[NL80211_ATTR_REG_ALPHA2] = { .type = NLA_STRING, .len = 2 },
+	/* allow 3 for NUL-termination, we used to declare this NLA_STRING */
+	[NL80211_ATTR_REG_ALPHA2] = NLA_POLICY_RANGE(NLA_BINARY, 2, 3),
 	[NL80211_ATTR_REG_RULES] = { .type = NLA_NESTED },
 
 	[NL80211_ATTR_BSS_CTS_PROT] = { .type = NLA_U8 },