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From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date:   Fri, 14 Jan 2022 15:00:41 -0800
Message-ID: <CABBYNZ+b4MehqjjXt7gZYi=b0yRrNRvYgTAJqjmy8Z+fM3SNjw@mail.gmail.com>
Subject: Re: [PATCH] Bluetooth: ensure valid channel mode when creating l2cap
 conn on LE
To:     gav@thegavinli.com
Cc:     Marcel Holtmann <marcel@holtmann.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>,
        Gavin Li <git@thegavinli.com>
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Hi,

On Fri, Jan 14, 2022 at 2:52 PM Luiz Augusto von Dentz
<luiz.dentz@gmail.com> wrote:
>
> Hi,
>
> On Wed, Jan 12, 2022 at 2:17 AM <gav@thegavinli.com> wrote:
> >
> > From: Gavin Li <git@thegavinli.com>
> >
> > After creating a socket(AF_INET, SOCK_STREAM, BTPROTO_L2CAP) socket and
> > connect()'ing to a LE device with default settings (no setsockopt), upon
> > the first sendmsg, the following BUG occurs because chan->mode==L2CAP_MODE_ERTM,
> > causing l2cap_ertm_send() -> __set_retrans_timer() -> schedule_delayed_work()
> > on l2cap_chan.retrans_timer, which was never initialized because
> > l2cap_ertm_init() was never called to initialize it.
> >
> >   Call Trace:
> >    queue_delayed_work_on+0x36/0x40
> >    l2cap_ertm_send.isra.0+0x14d/0x2d0 [bluetooth]
> >    l2cap_tx+0x361/0x510 [bluetooth]
> >    l2cap_chan_send+0xb26/0xb50 [bluetooth]
> >    l2cap_sock_sendmsg+0xc9/0x100 [bluetooth]
> >    sock_sendmsg+0x5e/0x60
> >    sock_write_iter+0x97/0x100
> >    new_sync_write+0x1d3/0x1f0
> >    vfs_write+0x1b4/0x270
> >    ksys_write+0xaf/0xe0
> >    do_syscall_64+0x33/0x40
> >    entry_SYSCALL_64_after_hwframe+0x44/0xa9
> >
> > This patch ensures that when connecting to a LE device, chan->mode will
> > always be corrected to L2CAP_MODE_LE_FLOWCTL if it is invalid for LE.
> >
> > Signed-off-by: Gavin Li <git@thegavinli.com>
> > ---
> >  net/bluetooth/l2cap_sock.c | 15 +++++++++++++--
> >  1 file changed, 13 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
> > index 160c016a5dfb9..58c06ef32656c 100644
> > --- a/net/bluetooth/l2cap_sock.c
> > +++ b/net/bluetooth/l2cap_sock.c
> > @@ -78,6 +78,17 @@ static int l2cap_validate_le_psm(u16 psm)
> >         return 0;
> >  }
> >
> > +static bool l2cap_mode_supports_le(u8 mode)
> > +{
> > +       switch (mode) {
> > +               case L2CAP_MODE_LE_FLOWCTL:
> > +               case L2CAP_MODE_EXT_FLOWCTL:
> > +                       return true;
> > +               default:
> > +                       return false;
> > +       }
> > +}
> > +
> >  static int l2cap_sock_bind(struct socket *sock, struct sockaddr *addr, int alen)
> >  {
> >         struct sock *sk = sock->sk;
> > @@ -161,7 +172,7 @@ static int l2cap_sock_bind(struct socket *sock, struct sockaddr *addr, int alen)
> >                 break;
> >         }
> >
> > -       if (chan->psm && bdaddr_type_is_le(chan->src_type))
> > +       if (chan->psm && bdaddr_type_is_le(la.l2_bdaddr_type) && !l2cap_mode_supports_le(chan->mode))
> >                 chan->mode = L2CAP_MODE_LE_FLOWCTL;
> >
> >         chan->state = BT_BOUND;
> > @@ -240,7 +251,7 @@ static int l2cap_sock_connect(struct socket *sock, struct sockaddr *addr,
> >                         return -EINVAL;
> >         }
> >
> > -       if (chan->psm && bdaddr_type_is_le(chan->src_type) && !chan->mode)
> > +       if (chan->psm && bdaddr_type_is_le(la.l2_bdaddr_type) && !l2cap_mode_supports_le(chan->mode))
> >                 chan->mode = L2CAP_MODE_LE_FLOWCTL;
> >
> >         err = l2cap_chan_connect(chan, la.l2_psm, __le16_to_cpu(la.l2_cid),
> > --
> > 2.34.1
>
> Doesn't apply to bluetooth-next:
>
> https://github.com/bluez/bluez/issues/250

Please disregard the link above, Ive meant to paste:

Applying: Bluetooth: ensure valid channel mode when creating l2cap conn on LE
error: patch failed: net/bluetooth/l2cap_sock.c:161
error: net/bluetooth/l2cap_sock.c: patch does not apply

I did fix something similar:

https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth-next.git/commit/?id=30d57722732d9736554f85f75f9d7ad5402d192e

-- 
Luiz Augusto von Dentz