Re: [syzbot] [bluetooth?] KASAN: slab-use-after-free Read in l2cap_connect (2)

[Hillf Danton <hdanton@sina.com>]

On Sat, 07 Sep 2024 07:42:26 -0700
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    788220eee30d Merge tag 'pm-6.11-rc7' of git://git.kernel.o..
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1304189f980000

#syz test

--- x/include/net/bluetooth/hci_core.h
+++ y/include/net/bluetooth/hci_core.h
@@ -511,6 +511,7 @@ struct hci_dev {
 	struct sk_buff		*recv_event;
 
 	struct mutex		req_lock;
+	struct mutex		rx_lock;
 	wait_queue_head_t	req_wait_q;
 	__u32			req_status;
 	__u32			req_result;
--- x/net/bluetooth/hci_core.c
+++ y/net/bluetooth/hci_core.c
@@ -2507,6 +2507,7 @@ struct hci_dev *hci_alloc_dev_priv(int s
 
 	mutex_init(&hdev->lock);
 	mutex_init(&hdev->req_lock);
+	mutex_init(&hdev->rx_lock);
 
 	ida_init(&hdev->unset_handle_ida);
 
@@ -3977,6 +3978,7 @@ static void hci_rx_work(struct work_stru
 
 	BT_DBG("%s", hdev->name);
 
+	mutex_lock(&hdev->rx_lock);
 	/* The kcov_remote functions used for collecting packet parsing
 	 * coverage information from this background thread and associate
 	 * the coverage with the syscall's thread which originally injected
@@ -4043,6 +4045,7 @@ static void hci_rx_work(struct work_stru
 			break;
 		}
 	}
+	mutex_unlock(&hdev->rx_lock);
 }
 
 static void hci_send_cmd_sync(struct hci_dev *hdev, struct sk_buff *skb)
--- x/net/bluetooth/hci_sync.c
+++ y/net/bluetooth/hci_sync.c
@@ -325,9 +325,11 @@ static void hci_cmd_sync_work(struct wor
 			int err;
 
 			hci_req_sync_lock(hdev);
+			mutex_lock(&hdev->rx_lock);
 			err = entry->func(hdev, entry->data);
 			if (entry->destroy)
 				entry->destroy(hdev, entry->data, err);
+			mutex_unlock(&hdev->rx_lock);
 			hci_req_sync_unlock(hdev);
 		}
 
--