On Mon, Sep 30, 2024 at 3:30 PM Luiz Augusto von Dentz
<luiz.dentz@xxxxxxxxx> wrote:
>
> From: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx>
>
> rfcomm_sk_state_change attempts to use sock_lock so it must never be
> called with it locked but rfcomm_sock_ioctl always attempt to lock it
> causing the following trace:
>
> ======================================================
> WARNING: possible circular locking dependency detected
> 6.8.0-syzkaller-08951-gfe46a7dd189e #0 Not tainted
> ------------------------------------------------------
> syz-executor386/5093 is trying to acquire lock:
> ffff88807c396258 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1671 [inline]
> ffff88807c396258 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sk_state_change+0x5b/0x310 net/bluetooth/rfcomm/sock.c:73
>
> but task is already holding lock:
> ffff88807badfd28 (&d->lock){+.+.}-{3:3}, at: __rfcomm_dlc_close+0x226/0x6a0 net/bluetooth/rfcomm/core.c:491
>
> Reported-by: syzbot+d7ce59b06b3eb14fd218@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=d7ce59b06b3eb14fd218
> Fixes: 3241ad820dbb ("[Bluetooth] Add timestamp support to L2CAP, RFCOMM and SCO")
> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx>
> ---
> net/bluetooth/rfcomm/sock.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
> index 37d63d768afb..f48250e3f2e1 100644
> --- a/net/bluetooth/rfcomm/sock.c
> +++ b/net/bluetooth/rfcomm/sock.c
> @@ -865,9 +865,7 @@ static int rfcomm_sock_ioctl(struct socket *sock, unsigned int cmd, unsigned lon
>
> if (err == -ENOIOCTLCMD) {
> #ifdef CONFIG_BT_RFCOMM_TTY
> - lock_sock(sk);
> err = rfcomm_dev_ioctl(sk, cmd, (void __user *) arg);
> - release_sock(sk);
> #else
> err = -EOPNOTSUPP;
> #endif
> --
> 2.46.1
>
--
Luiz Augusto von Dentz
