[PATCH 1/1] nl80211: Prevent out-of-bounds read when processing NL80211_ATTR_REG_ALPHA2

[Lee Jones]

Checks are presently in place in validate_nla() to ensure strings
greater than 2 are not passed in by the user which could potentially
cause issues.

However, there is nothing to prevent userspace from only providing a
single (1) Byte as the data length parameter via nla_put().  If this
were to happen, it would cause an OOB read in regulatory_hint_user(),
since it makes assumptions that alpha2[0] and alpha2[1] will always be
accessible.

Add an additional check, to ensure enough data has been allocated to
hold both Bytes.

Cc: <stable@xxxxxxxxxxxxxxx>
Cc: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
Cc: linux-wireless@xxxxxxxxxxxxxxx
Cc: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
---
 net/wireless/nl80211.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index ee1c2b6b69711..80a516033db36 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -7536,6 +7536,10 @@ static int nl80211_req_set_reg(struct sk_buff *skb, struct genl_info *info)
 		if (!info->attrs[NL80211_ATTR_REG_ALPHA2])
 			return -EINVAL;
 
+		if (nla_len(info->attrs[NL80211_ATTR_REG_ALPHA2]) !=
+		    nl80211_policy[NL80211_ATTR_REG_ALPHA2].len)
+			return -EINVAL;
+
 		data = nla_data(info->attrs[NL80211_ATTR_REG_ALPHA2]);
 		return regulatory_hint_user(data, user_reg_hint_type);
 	case NL80211_USER_REG_HINT_INDOOR:
-- 
2.35.1.1094.g7c7d902a7c-goog