Commit 58ce6d5b authored by Tetsuo Handa's avatar Tetsuo Handa Committed by Luiz Augusto von Dentz
Browse files

Bluetooth: defer cleanup of resources in hci_unregister_dev() 

syzbot is hitting might_sleep() warning at hci_sock_dev_event()
due to calling lock_sock() with rw spinlock held [1].

It seems that history of this locking problem is a trial and error.

Commit b40df574 ("[PATCH] bluetooth: fix socket locking in
hci_sock_dev_event()") in 2.6.21-rc4 changed bh_lock_sock() to lock_sock()
as an attempt to fix lockdep warning.

Then, commit 4ce61d1c ("[BLUETOOTH]: Fix locking in
hci_sock_dev_event().") in 2.6.22-rc2 changed lock_sock() to
local_bh_disable() + bh_lock_sock_nested() as an attempt to fix
sleep in atomic context warning.

Then, commit 4b5dd696 ("Bluetooth: Remove local_bh_disable() from
hci_sock.c") in 3.3-rc1 removed local_bh_disable().

Then, commit e305509e ("Bluetooth: use correct lock to prevent UAF
of hdev object") in 5.13-rc5 again changed bh_lock_sock_nested() to
lock_sock() as an attempt to fix CVE-2021-3573.

This difficulty comes from current implementation that
hci_sock_dev_event(HCI_DEV_UNREG) is responsible for dropping all
references from sockets because hci_unregister_dev() immediately reclaims
resources as soon as returning from hci_sock_dev_event(HCI_DEV_UNREG).
But the history suggests that hci_sock_dev_event(HCI_DEV_UNREG) was not
doing what it should do.

Therefore, instead of trying to detach sockets from device, let's accept
not detaching sockets from device at hci_sock_dev_event(HCI_DEV_UNREG),
by moving actual cleanup of resources from hci_unregister_dev() to
hci_release_dev() which is called by bt_host_release when all references
to this unregistered device (which is a kobject) are gone.

Link: https://syzkaller.appspot.com/bug?extid=a5df189917e79d5e59c9

 [1]
Reported-by: default avatarsyzbot <syzbot+a5df189917e79d5e59c9@syzkaller.appspotmail.com>
Signed-off-by: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Tested-by: default avatarsyzbot <syzbot+a5df189917e79d5e59c9@syzkaller.appspotmail.com>
Fixes: e305509e ("Bluetooth: use correct lock to prevent UAF of hdev object")
Signed-off-by: default avatarLuiz Augusto von Dentz <luiz.von.dentz@intel.com>
parent acd5aea4

include/net/bluetooth/hci_core.h

+1 −0
Original line number Diff line number Diff line
@@ -1230,6 +1230,7 @@ struct hci_dev *hci_alloc_dev(void); 
void hci_free_dev(struct hci_dev *hdev);

int hci_register_dev(struct hci_dev *hdev);

void hci_unregister_dev(struct hci_dev *hdev);

void hci_release_dev(struct hci_dev *hdev);

int hci_suspend_dev(struct hci_dev *hdev);

int hci_resume_dev(struct hci_dev *hdev);

int hci_reset_dev(struct hci_dev *hdev);

net/bluetooth/hci_core.c

+9 −8
Original line number Diff line number Diff line
@@ -3996,14 +3996,10 @@ EXPORT_SYMBOL(hci_register_dev); 
/* Unregister HCI device */

void hci_unregister_dev(struct hci_dev *hdev)

{

	int id;



	BT_DBG("%p name %s bus %d", hdev, hdev->name, hdev->bus);



	hci_dev_set_flag(hdev, HCI_UNREGISTER);



	id = hdev->id;



	write_lock(&hci_dev_list_lock);

	list_del(&hdev->list);

	write_unlock(&hci_dev_list_lock);
@@ -4038,7 +4034,13 @@ void hci_unregister_dev(struct hci_dev *hdev) 
	}



	device_del(&hdev->dev);

	hci_dev_put(hdev);

}

EXPORT_SYMBOL(hci_unregister_dev);



/* Release HCI device */

void hci_release_dev(struct hci_dev *hdev)

{

	debugfs_remove_recursive(hdev->debugfs);

	kfree_const(hdev->hw_info);

	kfree_const(hdev->fw_info);
@@ -4063,11 +4065,10 @@ void hci_unregister_dev(struct hci_dev *hdev) 
	hci_blocked_keys_clear(hdev);

	hci_dev_unlock(hdev);



	hci_dev_put(hdev);



	ida_simple_remove(&hci_index_ida, id);

	ida_simple_remove(&hci_index_ida, hdev->id);

	kfree(hdev);

}

EXPORT_SYMBOL(hci_unregister_dev);

EXPORT_SYMBOL(hci_release_dev);



/* Suspend HCI device */

int hci_suspend_dev(struct hci_dev *hdev)

net/bluetooth/hci_sock.c

+13 −7
Original line number Diff line number Diff line
@@ -759,19 +759,13 @@ void hci_sock_dev_event(struct hci_dev *hdev, int event) 
	if (event == HCI_DEV_UNREG) {

		struct sock *sk;



		/* Detach sockets from device */

		/* Wake up sockets using this dead device */

		read_lock(&hci_sk_list.lock);

		sk_for_each(sk, &hci_sk_list.head) {

			lock_sock(sk);

			if (hci_pi(sk)->hdev == hdev) {

				hci_pi(sk)->hdev = NULL;

				sk->sk_err = EPIPE;

				sk->sk_state = BT_OPEN;

				sk->sk_state_change(sk);



				hci_dev_put(hdev);

			}

			release_sock(sk);

		}

		read_unlock(&hci_sk_list.lock);

	}
@@ -1103,6 +1097,18 @@ static int hci_sock_bind(struct socket *sock, struct sockaddr *addr, 


	lock_sock(sk);



	/* Allow detaching from dead device and attaching to alive device, if

	 * the caller wants to re-bind (instead of close) this socket in

	 * response to hci_sock_dev_event(HCI_DEV_UNREG) notification.

	 */

	hdev = hci_pi(sk)->hdev;

	if (hdev && hci_dev_test_flag(hdev, HCI_UNREGISTER)) {

		hci_pi(sk)->hdev = NULL;

		sk->sk_state = BT_OPEN;

		hci_dev_put(hdev);

	}

	hdev = NULL;



	if (sk->sk_state == BT_BOUND) {

		err = -EALREADY;

		goto done;

net/bluetooth/hci_sysfs.c

+1 −1
Original line number Diff line number Diff line
@@ -83,7 +83,7 @@ void hci_conn_del_sysfs(struct hci_conn *conn) 
static void bt_host_release(struct device *dev)

{

	struct hci_dev *hdev = to_hci_dev(dev);

	kfree(hdev);

	hci_release_dev(hdev);

	module_put(THIS_MODULE);

}