wifi: mac80211_hwsim: reject undersized HWSIM_ATTR_TX_INFO

hwsim_tx_info_frame_received_nl() casts the HWSIM_ATTR_TX_INFO payload to a struct hwsim_tx_rate * and unconditionally reads IEEE80211_TX_MAX_RATES entries (8 bytes) from it. The policy only bounds the attribute from above (NLA_BINARY .len is a maximum) and the op sets GENL_DONT_VALIDATE_STRICT, so a short or zero-length attribute is accepted and the loop reads past the payload.

Require the exact length in the policy, so a malformed attribute is rejected before the handler runs.

---
v2: enforce the length via NLA_POLICY_EXACT_LEN in the policy instead of
a manual nla_len() check in the handler, and trim the changelog, per Johannes Berg's review.

 drivers/net/wireless/virtual/mac80211_hwsim_main.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

index 0dd8a6c85953..836dd25e5c61 100644
@@ -870,9 +870,9 @@ static const struct nla_policy hwsim_genl_policy[HWSIM_ATTR_MAX + 1] = {
 	[HWSIM_ATTR_FLAGS] = { .type = NLA_U32 },
 	[HWSIM_ATTR_RX_RATE] = { .type = NLA_U32 },
 	[HWSIM_ATTR_SIGNAL] = { .type = NLA_U32 },
-	[HWSIM_ATTR_TX_INFO] = { .type = NLA_BINARY,
-				 .len = IEEE80211_TX_MAX_RATES *
-					sizeof(struct hwsim_tx_rate)},
+	[HWSIM_ATTR_TX_INFO] =
+		NLA_POLICY_EXACT_LEN(IEEE80211_TX_MAX_RATES *
+				     sizeof(struct hwsim_tx_rate)),
 	[HWSIM_ATTR_COOKIE] = { .type = NLA_U64 },
 	[HWSIM_ATTR_CHANNELS] = { .type = NLA_U32 },
 	[HWSIM_ATTR_RADIO_ID] = { .type = NLA_U32 },

2.50.1 (Apple Git-155)