syzbot is hitting might_sleep() warning at hci_sock_dev_event() due to calling lock_sock() with rw spinlock held [1]. Defer calling lock_sock() via sock_hold(). Link: https://syzkaller.appspot.com/bug?extid=a5df189917e79d5e59c9 [1] Reported-by: syzbot <syzbot+a5df189917e79d5e59c9@xxxxxxxxxxxxxxxxxxxxxxxxx> Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Tested-by: syzbot <syzbot+a5df189917e79d5e59c9@xxxxxxxxxxxxxxxxxxxxxxxxx> Fixes: e305509e678b3a4a ("Bluetooth: use correct lock to prevent UAF of hdev object") --- Changes in v2: Take hci_sk_list.lock for write in case bt_sock_unlink() is called after sk_hashed(sk) test, and defer hci_dev_put(hdev) till schedulable context. net/bluetooth/hci_sock.c | 32 +++++++++++++++++++++++++++++--- 1 file changed, 29 insertions(+), 3 deletions(-) diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c index b04a5a02ecf3..d8e1ac1ae10d 100644 --- a/net/bluetooth/hci_sock.c +++ b/net/bluetooth/hci_sock.c @@ -758,20 +758,46 @@ void hci_sock_dev_event(struct hci_dev *hdev, int event) if (event == HCI_DEV_UNREG) { struct sock *sk; + bool put_dev; +restart: + put_dev = false; /* Detach sockets from device */ read_lock(&hci_sk_list.lock); sk_for_each(sk, &hci_sk_list.head) { + /* hci_sk_list.lock is preventing hci_sock_release() + * from calling bt_sock_unlink(). + */ + if (hci_pi(sk)->hdev != hdev || sk_unhashed(sk)) + continue; + /* Take a ref because we can't call lock_sock() with + * hci_sk_list.lock held. + */ + sock_hold(sk); + read_unlock(&hci_sk_list.lock); lock_sock(sk); - if (hci_pi(sk)->hdev == hdev) { + /* Since hci_sock_release() might have already called + * bt_sock_unlink() while waiting for lock_sock(), + * use sk_hashed(sk) for checking that bt_sock_unlink() + * is not yet called. + */ + write_lock(&hci_sk_list.lock); + if (sk_hashed(sk) && 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); + put_dev = true; } + write_unlock(&hci_sk_list.lock); release_sock(sk); + sock_put(sk); + if (put_dev) + hci_dev_put(hdev); + /* Restarting is safe, for hci_pi(sk)->hdev != hdev if + * condition met and sk_unhashed(sk) == true otherwise. + */ + goto restart; } read_unlock(&hci_sk_list.lock); } -- 2.18.4
