On Fri, Apr 26, 2024 at 5:16 AM Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
>
> On Fri, Apr 26, 2024 at 03:20:05AM -0400, Sungwoo Kim wrote:
> > diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
> > index 84fc70862..a8f414ab8 100644
> > --- a/net/bluetooth/l2cap_core.c
> > +++ b/net/bluetooth/l2cap_core.c
> > @@ -3953,6 +3953,9 @@ static struct l2cap_chan *l2cap_connect(struct l2cap_conn *conn,
> > if (!chan)
> > goto response;
> >
> > + l2cap_chan_hold(chan);
> > + l2cap_chan_lock(chan);
> > +
> > /* For certain devices (ex: HID mouse), support for authentication,
> > * pairing and bonding is optional. For such devices, inorder to avoid
> > * the ACL alive for too long after L2CAP disconnection, reset the ACL
> > @@ -4041,6 +4044,11 @@ static struct l2cap_chan *l2cap_connect(struct l2cap_conn *conn,
> > chan->num_conf_req++;
> > }
> >
> > + if (chan) {
> > + l2cap_chan_unlock(chan);
> > + l2cap_chan_put(chan);
> > + }
> > +
> > return chan;
> ^^^^^^^^^^^^
> This doesn't fix the bug because we're returning chan.
>
> As soon as you call l2cap_chan_put() then chan will be freed by in the
> other thread which is doing l2cap_conn_del() resulting in a use after
> free in the caller.
Thank you for pointing this out.
No caller uses the return value of l2cap_connect() if the kernel
versions >= v6.9.
So, l2cap_connect() can return void.
One caller uses the return value of l2cap_connect() in v4.19 <= the
kernel versions <= v6.8.
In this case, the caller should unlock and put a channel.
Question: Can different patches be applied for different versions like
the above?
Thanks,
Sungwoo Kim.
