linux-kernel - Re: [syzbot] [bluetooth?] [usb?] memory leak in __hci_cmd_sync

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Message-ID: <tencent_E01B774BC11B3D25D0BA9DBB46334C9E1E08@qq.com>
Date: Fri, 21 Nov 2025 08:57:40 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+f098d64cc684b8dbaf65@...kaller.appspotmail.com
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bluetooth?] [usb?] memory leak in __hci_cmd_sync_sk

#syz test

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 3418d7b964a1..62469dba9e63 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -1466,7 +1466,7 @@ static void hci_cmd_timeout(struct work_struct *work)
 	if (hdev->req_skb) {
 		u16 opcode = hci_skb_opcode(hdev->req_skb);
 
-		bt_dev_err(hdev, "command 0x%4.4x tx timeout", opcode);
+		bt_dev_err(hdev, "command 0x%4.4x skb: %p tx timeout", opcode, hdev->req_skb);
 
 		hci_cmd_sync_cancel_sync(hdev, ETIMEDOUT);
 	} else {
diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index 6e76798ec786..7fc79b7ee4b9 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -133,6 +133,8 @@ static int hci_req_sync_run(struct hci_request *req)
 		return -ENODATA;
 
 	skb = skb_peek_tail(&req->cmd_q);
+	printk("status: %u, result: %u, skb: %p, %s\n",
+		hdev->req_status, hdev->req_result, skb, __func__);
 	bt_cb(skb)->hci.req_complete_skb = hci_cmd_sync_complete;
 	bt_cb(skb)->hci.req_flags |= HCI_REQ_SKB;
 
@@ -158,8 +160,9 @@ struct sk_buff *__hci_cmd_sync_sk(struct hci_dev *hdev, u16 opcode, u32 plen,
 				  struct sock *sk)
 {
 	struct hci_request req;
-	struct sk_buff *skb;
+	struct sk_buff *skb, *skb_tail;
 	int err = 0;
+	unsigned long flags;
 
 	bt_dev_dbg(hdev, "Opcode 0x%4.4x", opcode);
 
@@ -169,6 +172,7 @@ struct sk_buff *__hci_cmd_sync_sk(struct hci_dev *hdev, u16 opcode, u32 plen,
 
 	hdev->req_status = HCI_REQ_PEND;
 
+	skb_tail = skb_peek_tail(&req.cmd_q);
 	err = hci_req_sync_run(&req);
 	if (err < 0)
 		return ERR_PTR(err);
@@ -201,18 +205,35 @@ struct sk_buff *__hci_cmd_sync_sk(struct hci_dev *hdev, u16 opcode, u32 plen,
 
 	bt_dev_dbg(hdev, "end: err %d", err);
 
+	printk("err: %d, status: %u, result: %u, skb: %p, %s\n",
+		err, hdev->req_status, hdev->req_result, skb, __func__);
 	if (err < 0) {
 		kfree_skb(skb);
-		return ERR_PTR(err);
+		goto out;
 	}
 
 	/* If command return a status event skb will be set to NULL as there are
 	 * no parameters.
 	 */
-	if (!skb)
-		return ERR_PTR(-ENODATA);
+	if (!skb) {
+		err = -ENODATA;
+		goto out;
+	}
 
 	return skb;
+
+out:
+	if (!skb_queue_empty(&hdev->cmd_q)) {
+		spin_lock_irqsave(&hdev->cmd_q.lock, flags);
+		skb = __skb_dequeue_tail(&hdev->cmd_q);
+		spin_unlock_irqrestore(&hdev->cmd_q.lock, flags);
+	} else
+		skb = skb_tail;
+
+	printk("remove skb: %p, %s\n", skb,  __func__);
+	kfree_skb(skb);
+
+	return ERR_PTR(err);
 }
 EXPORT_SYMBOL(__hci_cmd_sync_sk);