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
b40df5743ee8aed8 ("[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
4ce61d1c7a8ef4c1 ("[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
4b5dd696f81b210c ("Bluetooth: Remove local_bh_disable() from
hci_sock.c") in 3.3-rc1 removed local_bh_disable().
Then, commit
e305509e678b3a4a ("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
Reported-by: syzbot <syzbot+a5df189917e79d5e59c9@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Tested-by: syzbot <syzbot+a5df189917e79d5e59c9@syzkaller.appspotmail.com>
Fixes:
e305509e678b3a4a ("Bluetooth: use correct lock to prevent UAF of hdev object")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
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);
/* 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);
}
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);
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)
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);
}
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;
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);
}