wifi: ath9k: delay all of ath9k_wmi_event_tasklet() until init is complete

jira LE-1907
cve CVE-2024-26897
Rebuild_History Non-Buildable kernel-5.14.0-427.31.1.el9_4
commit-author Toke Høiland-Jørgensen <toke@redhat.com>
commit 24355fc

The ath9k_wmi_event_tasklet() used in ath9k_htc assumes that all the data
structures have been fully initialised by the time it runs. However, because of
the order in which things are initialised, this is not guaranteed to be the
case, because the device is exposed to the USB subsystem before the ath9k driver
initialisation is completed.

We already committed a partial fix for this in commit:
8b3046a ("ath9k_htc: fix NULL pointer dereference at ath9k_htc_tx_get_packet()")

However, that commit only aborted the WMI_TXSTATUS_EVENTID command in the event
tasklet, pairing it with an "initialisation complete" bit in the TX struct. It
seems syzbot managed to trigger the race for one of the other commands as well,
so let's just move the existing synchronisation bit to cover the whole
tasklet (setting it at the end of ath9k_htc_probe_device() instead of inside
ath9k_tx_init()).

Link: https://lore.kernel.org/r/ed1d2c66-1193-4c81-9542-d514c29ba8b8.bugreport@ubisectech.com
Fixes: 8b3046a ("ath9k_htc: fix NULL pointer dereference at ath9k_htc_tx_get_packet()")
	Reported-by: Ubisectech Sirius <bugreport@ubisectech.com>
	Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
	Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://msgid.link/20240126140218.1033443-1-toke@toke.dk
(cherry picked from commit 24355fc)
	Signed-off-by: Jonathan Maple <jmaple@ciq.com>

Author: PlaidCat

drivers/net/wireless/ath/ath9k/htc.h

@@ -306,7 +306,6 @@ struct ath9k_htc_tx {
 	DECLARE_BITMAP(tx_slot, MAX_TX_BUF_NUM);
 	struct timer_list cleanup_timer;
 	spinlock_t tx_lock;
-	bool initialized;
 };
 
 struct ath9k_htc_tx_ctl {
@@ -515,6 +514,7 @@ struct ath9k_htc_priv {
 	unsigned long ps_usecount;
 	bool ps_enabled;
 	bool ps_idle;
+	bool initialized;
 
 #ifdef CONFIG_MAC80211_LEDS
 	enum led_brightness brightness;

drivers/net/wireless/ath/ath9k/htc_drv_init.c

@@ -966,6 +966,10 @@ int ath9k_htc_probe_device(struct htc_target *htc_handle, struct device *dev,
 
 	htc_handle->drv_priv = priv;
 
+	/* Allow ath9k_wmi_event_tasklet() to operate. */
+	smp_wmb();
+	priv->initialized = true;
+
 	return 0;
 
 err_init:

drivers/net/wireless/ath/ath9k/htc_drv_txrx.c

@@ -814,10 +814,6 @@ int ath9k_tx_init(struct ath9k_htc_priv *priv)
 	skb_queue_head_init(&priv->tx.data_vo_queue);
 	skb_queue_head_init(&priv->tx.tx_failed);
 
-	/* Allow ath9k_wmi_event_tasklet(WMI_TXSTATUS_EVENTID) to operate. */
-	smp_wmb();
-	priv->tx.initialized = true;
-
 	return 0;
 }
 

drivers/net/wireless/ath/ath9k/wmi.c

@@ -155,6 +155,12 @@ void ath9k_wmi_event_tasklet(struct tasklet_struct *t)
 		}
 		spin_unlock_irqrestore(&wmi->wmi_lock, flags);
 
+		/* Check if ath9k_htc_probe_device() completed. */
+		if (!data_race(priv->initialized)) {
+			kfree_skb(skb);
+			continue;
+		}
+
 		hdr = (struct wmi_cmd_hdr *) skb->data;
 		cmd_id = be16_to_cpu(hdr->command_id);
 		wmi_event = skb_pull(skb, sizeof(struct wmi_cmd_hdr));
@@ -169,10 +175,6 @@ void ath9k_wmi_event_tasklet(struct tasklet_struct *t)
 					     &wmi->drv_priv->fatal_work);
 			break;
 		case WMI_TXSTATUS_EVENTID:
-			/* Check if ath9k_tx_init() completed. */
-			if (!data_race(priv->tx.initialized))
-				break;
-
 			spin_lock_bh(&priv->tx.tx_lock);
 			if (priv->tx.flags & ATH9K_HTC_OP_TX_DRAIN) {
 				spin_unlock_bh(&priv->tx.tx_lock);