wifi: virt_wifi: avoid reporting connection success with wrong SSID

When user issues a connection with a different SSID than the one
virt_wifi has advertised, the __cfg80211_connect_result() will
trigger the warning: WARN_ON(bss_not_found).

The issue is because the connection code in virt_wifi does not
check the SSID from user space (it only checks the BSSID), and
virt_wifi will call cfg80211_connect_result() with WLAN_STATUS_SUCCESS
even if the SSID is different from the one virt_wifi has advertised.
Eventually cfg80211 won't be able to find the cfg80211_bss and generate
the warning.

Fixed it by checking the SSID (from user space) in the connection code.

Fixes: c7cdba31 ("mac80211-next: rtnetlink wifi simulation device")
Reported-by: syzbot+d6eb9cee2885ec06f5e3@syzkaller.appspotmail.com
Signed-off-by: En-Wei Wu <en-wei.wu@canonical.com>
Link: https://patch.msgid.link/20240705023756.10954-1-en-wei.wu@canonical.comSigned-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/virtual/virt_wifi.c

@@ -136,6 +136,8 @@ static struct ieee80211_supported_band band_5ghz = {
 /* Assigned at module init. Guaranteed locally-administered and unicast. */
 static u8 fake_router_bssid[ETH_ALEN] __ro_after_init = {};
 
+#define VIRT_WIFI_SSID "VirtWifi"
+
 static void virt_wifi_inform_bss(struct wiphy *wiphy)
 {
 	u64 tsf = div_u64(ktime_get_boottime_ns(), 1000);
@@ -146,8 +148,8 @@ static void virt_wifi_inform_bss(struct wiphy *wiphy)
 		u8 ssid[8];
 	} __packed ssid = {
 		.tag = WLAN_EID_SSID,
-		.len = 8,
-		.ssid = "VirtWifi",
+		.len = strlen(VIRT_WIFI_SSID),
+		.ssid = VIRT_WIFI_SSID,
 	};
 
 	informed_bss = cfg80211_inform_bss(wiphy, &channel_5ghz,
@@ -213,6 +215,8 @@ struct virt_wifi_netdev_priv {
 	struct net_device *upperdev;
 	u32 tx_packets;
 	u32 tx_failed;
+	u32 connect_requested_ssid_len;
+	u8 connect_requested_ssid[IEEE80211_MAX_SSID_LEN];
 	u8 connect_requested_bss[ETH_ALEN];
 	bool is_up;
 	bool is_connected;
@@ -229,6 +233,12 @@ static int virt_wifi_connect(struct wiphy *wiphy, struct net_device *netdev,
 	if (priv->being_deleted || !priv->is_up)
 		return -EBUSY;
 
+	if (!sme->ssid)
+		return -EINVAL;
+
+	priv->connect_requested_ssid_len = sme->ssid_len;
+	memcpy(priv->connect_requested_ssid, sme->ssid, sme->ssid_len);
+
 	could_schedule = schedule_delayed_work(&priv->connect, HZ * 2);
 	if (!could_schedule)
 		return -EBUSY;
@@ -252,12 +262,15 @@ static void virt_wifi_connect_complete(struct work_struct *work)
 		container_of(work, struct virt_wifi_netdev_priv, connect.work);
 	u8 *requested_bss = priv->connect_requested_bss;
 	bool right_addr = ether_addr_equal(requested_bss, fake_router_bssid);
+	bool right_ssid = priv->connect_requested_ssid_len == strlen(VIRT_WIFI_SSID) &&
+			  !memcmp(priv->connect_requested_ssid, VIRT_WIFI_SSID,
+				  priv->connect_requested_ssid_len);
 	u16 status = WLAN_STATUS_SUCCESS;
 
 	if (is_zero_ether_addr(requested_bss))
 		requested_bss = NULL;
 
-	if (!priv->is_up || (requested_bss && !right_addr))
+	if (!priv->is_up || (requested_bss && !right_addr) || !right_ssid)
 		status = WLAN_STATUS_UNSPECIFIED_FAILURE;
 	else
 		priv->is_connected = true;