Re: general protection fault in ath9k_wmi_event_tasklet

[Toke Høiland-Jørgensen]

"Ubisectech Sirius" <bugreport@xxxxxxxxxxxxxx> writes:

> Hello.
> We are Ubisectech Sirius Team, the vulnerability lab of China ValiantSec. Recently, our team has discovered a issue in Linux kernel 6.7.0-g9d1694dc91ce. Attached to the email were a POC file of the issue.
> Stack dump:
> general protection fault, probably for non-canonical address 0xdffffc0000000038: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x00000000000001c0-0x00000000000001c7]
> CPU: 0 PID: 16 Comm: ksoftirqd/0 Not tainted 6.7.0-g9d1694dc91ce #20
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
> RIP: 0010:__queue_work+0x9d/0x1160 kernel/workqueue.c:1727
> Call Trace:
> <TASK>
> queue_work_on+0xf2/0x110 kernel/workqueue.c:1837
> queue_work include/linux/workqueue.h:548 [inline]
> ieee80211_queue_work net/mac80211/util.c:898 [inline]
> ieee80211_queue_work+0x111/0x180 net/mac80211/util.c:891
> ath9k_wmi_event_tasklet+0x327/0x450 drivers/net/wireless/ath/ath9k/wmi.c:168
> tasklet_action_common.constprop.0+0x229/0x390 kernel/softirq.c:780
> __do_softirq+0x1d4/0x85e kernel/softirq.c:553
> run_ksoftirqd kernel/softirq.c:921 [inline]
> run_ksoftirqd+0x31/0x60 kernel/softirq.c:913
> smpboot_thread_fn+0x63c/0x9f0 kernel/smpboot.c:164
> kthread+0x2cc/0x3b0 kernel/kthread.c:388
> ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
> ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242
> </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:__queue_work+0x9d/0x1160 kernel/workqueue.c:1727
> Thank you for taking the time to read this email and we look forward
> to working with you further.

Hmm, so from eyeballing the code in question, this looks like it is
another initialisation race along the lines of the one fixed in commit:
8b3046abc99e ("ath9k_htc: fix NULL pointer dereference at ath9k_htc_tx_get_packet()")

Could you please test the patch below and see if you can still reproduce
this issue with that applied?

-Toke



diff --git a/drivers/net/wireless/ath/ath9k/htc.h b/drivers/net/wireless/ath/ath9k/htc.h
index 237f4ec2cffd..6c33e898b300 100644
--- a/drivers/net/wireless/ath/ath9k/htc.h
+++ b/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;
diff --git a/drivers/net/wireless/ath/ath9k/htc_drv_init.c b/drivers/net/wireless/ath/ath9k/htc_drv_init.c
index dae3d9c7b640..fc339079ee8c 100644
--- a/drivers/net/wireless/ath/ath9k/htc_drv_init.c
+++ b/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:
diff --git a/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c b/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c
index 672789e3c55d..768ed8ea5c9f 100644
--- a/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c
+++ b/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;
 }
 
diff --git a/drivers/net/wireless/ath/ath9k/wmi.c b/drivers/net/wireless/ath/ath9k/wmi.c
index 1476b42b52a9..805ad31edba2 100644
--- a/drivers/net/wireless/ath/ath9k/wmi.c
+++ b/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);