ath10k: fix use-after-free in ath10k_wmi_cmd_send_nowait

The skb may be freed in tx completion context before
trace_ath10k_wmi_cmd is called. This can be easily captured when
KASAN(Kernel Address Sanitizer) is enabled. The fix is to move
trace_ath10k_wmi_cmd before the send operation. As the ret has no
meaning in trace_ath10k_wmi_cmd then, so remove this parameter too.

Signed-off-by: Carl Huang <cjhuang@codeaurora.org>
Tested-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/ath/ath10k/trace.h

@@ -152,10 +152,9 @@ TRACE_EVENT(ath10k_log_dbg_dump,
 );
 
 TRACE_EVENT(ath10k_wmi_cmd,
-	TP_PROTO(struct ath10k *ar, int id, const void *buf, size_t buf_len,
-		 int ret),
+	TP_PROTO(struct ath10k *ar, int id, const void *buf, size_t buf_len),
 
-	TP_ARGS(ar, id, buf, buf_len, ret),
+	TP_ARGS(ar, id, buf, buf_len),
 
 	TP_STRUCT__entry(
 		__string(device, dev_name(ar->dev))
@@ -163,7 +162,6 @@ TRACE_EVENT(ath10k_wmi_cmd,
 		__field(unsigned int, id)
 		__field(size_t, buf_len)
 		__dynamic_array(u8, buf, buf_len)
-		__field(int, ret)
 	),
 
 	TP_fast_assign(
@@ -171,17 +169,15 @@ TRACE_EVENT(ath10k_wmi_cmd,
 		__assign_str(driver, dev_driver_string(ar->dev));
 		__entry->id = id;
 		__entry->buf_len = buf_len;
-		__entry->ret = ret;
 		memcpy(__get_dynamic_array(buf), buf, buf_len);
 	),
 
 	TP_printk(
-		"%s %s id %d len %zu ret %d",
+		"%s %s id %d len %zu",
 		__get_str(driver),
 		__get_str(device),
 		__entry->id,
-		__entry->buf_len,
-		__entry->ret
+		__entry->buf_len
 	)
 );
 

drivers/net/wireless/ath/ath10k/wmi.c

@@ -1747,8 +1747,8 @@ int ath10k_wmi_cmd_send_nowait(struct ath10k *ar, struct sk_buff *skb,
 	cmd_hdr->cmd_id = __cpu_to_le32(cmd);
 
 	memset(skb_cb, 0, sizeof(*skb_cb));
+	trace_ath10k_wmi_cmd(ar, cmd_id, skb->data, skb->len);
 	ret = ath10k_htc_send(&ar->htc, ar->wmi.eid, skb);
-	trace_ath10k_wmi_cmd(ar, cmd_id, skb->data, skb->len, ret);
 
 	if (ret)
 		goto err_pull;