Re: [PATCH 5.4 39/78] Bluetooth: use correct lock to prevent UAF of hdev object

On Mon, Jun 14, 2021 at 04:15:02PM +0200, Eric Dumazet wrote:

On 6/8/21 8:27 PM, Greg Kroah-Hartman wrote:

quoted

From: Lin Ma <redacted>

commit e305509e678b3a4af2b3cfd410f409f7cdaabb52 upstream.

The hci_sock_dev_event() function will cleanup the hdev object for
sockets even if this object may still be in used within the
hci_sock_bound_ioctl() function, result in UAF vulnerability.

This patch replace the BH context lock to serialize these affairs
and prevent the race condition.

Signed-off-by: Lin Ma <redacted>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/bluetooth/hci_sock.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/bluetooth/hci_sock.c
+++ b/net/bluetooth/hci_sock.c

@@ -755,7 +755,7 @@ void hci_sock_dev_event(struct hci_dev *
 		/* Detach sockets from device */
 		read_lock(&hci_sk_list.lock);
 		sk_for_each(sk, &hci_sk_list.head) {
-			bh_lock_sock_nested(sk);
+			lock_sock(sk);
 			if (hci_pi(sk)->hdev == hdev) {
 				hci_pi(sk)->hdev = NULL;
 				sk->sk_err = EPIPE;

@@ -764,7 +764,7 @@ void hci_sock_dev_event(struct hci_dev *
 
 				hci_dev_put(hdev);
 			}
-			bh_unlock_sock(sk);
+			release_sock(sk);
 		}
 		read_unlock(&hci_sk_list.lock);
 	}

This patch is buggy.

lock_sock() can sleep.

But the read_lock(&hci_sk_list.lock) two lines before is not going to allow the sleep.

Hmmm ?

Odd, Lin, did you see any problems with your testing of this?