[PATCH] Bluetooth: fix use-after-free in hci_conn_drop

[Masahiro Kawada <youjingxiaogao2@gmail.com>]

Fix a use-after-free in hci_conn_drop triggered via hci_cmd_sync_work.

In hci_conn_del(), hci_cmd_sync_dequeue() is called after
hci_conn_cleanup() which may have already freed the conn pointer.
Fix by moving the dequeue before cleanup.

Additionally, le_read_features_complete() calls hci_conn_drop(conn)
without checking whether conn is still valid. When
hci_le_read_remote_features_sync() blocks waiting for an HCI event,
another thread can free conn through hci_conn_del(). Fix by adding
a hci_conn_valid() check before calling hci_conn_drop().

Fixes: 881559af5f5c ("Bluetooth: hci_sync: Attempt to dequeue connection attempt")
Fixes: a106e50be74b ("Bluetooth: HCI: Add support for LL Extended Feature Set")
Reported-by: syzbot+3609b9b48e68e1fe47fd@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=3609b9b48e68e1fe47fd
Tested-by: syzbot+3609b9b48e68e1fe47fd@syzkaller.appspotmail.com
Signed-off-by: Masahiro Kawada <youjingxiaogao2@gmail.com>
---
 net/bluetooth/hci_conn.c | 6 +++---
 net/bluetooth/hci_sync.c | 3 +++
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 0795818963a..aa3607327ad 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -1232,15 +1232,15 @@ void hci_conn_del(struct hci_conn *conn)
 	skb_queue_purge(&conn->data_q);
 	skb_queue_purge(&conn->tx_q.queue);
 
+	/* Dequeue callbacks using connection pointer as data */
+	hci_cmd_sync_dequeue(hdev, NULL, conn, NULL);
+
 	/* Remove the connection from the list and cleanup its remaining
 	 * state. This is a separate function since for some cases like
 	 * BT_CONNECT_SCAN we *only* want the cleanup part without the
 	 * rest of hci_conn_del.
 	 */
 	hci_conn_cleanup(conn);
-
-	/* Dequeue callbacks using connection pointer as data */
-	hci_cmd_sync_dequeue(hdev, NULL, conn, NULL);
 }
 
 struct hci_dev *hci_get_route(bdaddr_t *dst, bdaddr_t *src, uint8_t src_type)
diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index f04a90bce4a..f31086c187f 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -7371,6 +7371,9 @@ static void le_read_features_complete(struct hci_dev *hdev, void *data, int err)
 	if (err == -ECANCELED)
 		return;
 
+	if (!hci_conn_valid(hdev, conn))
+		return;
+
 	hci_conn_drop(conn);
 }
 
-- 
2.43.0