Re: [PATCH 1/1] Bluetooth: Use chan_list_lock to protect the whole put/destroy invokation

[Luiz Augusto von Dentz]

Hi Lee,

On Tue, Jun 21, 2022 at 11:35 AM Luiz Augusto von Dentz
<luiz.dentz@xxxxxxxxx> wrote:
>
> Hi Lee,
>
> On Tue, Jun 21, 2022 at 7:38 AM Lee Jones <lee.jones@xxxxxxxxxx> wrote:
> >
> > On Tue, 07 Jun 2022, Lee Jones wrote:
> >
> > > This change prevents a use-after-free caused by one of the worker
> > > threads starting up (see below) *after* the final channel reference
> > > has been put() during sock_close() but *before* the references to the
> > > channel have been destroyed.
> > >
> > >   refcount_t: increment on 0; use-after-free.
> > >   BUG: KASAN: use-after-free in refcount_dec_and_test+0x20/0xd0
> > >   Read of size 4 at addr ffffffc114f5bf18 by task kworker/u17:14/705
> > >
> > >   CPU: 4 PID: 705 Comm: kworker/u17:14 Tainted: G S      W       4.14.234-00003-g1fb6d0bd49a4-dirty #28
> > >   Hardware name: Qualcomm Technologies, Inc. SM8150 V2 PM8150 Google Inc. MSM sm8150 Flame DVT (DT)
> > >   Workqueue: hci0 hci_rx_work
> > >   Call trace:
> > >    dump_backtrace+0x0/0x378
> > >    show_stack+0x20/0x2c
> > >    dump_stack+0x124/0x148
> > >    print_address_description+0x80/0x2e8
> > >    __kasan_report+0x168/0x188
> > >    kasan_report+0x10/0x18
> > >    __asan_load4+0x84/0x8c
> > >    refcount_dec_and_test+0x20/0xd0
> > >    l2cap_chan_put+0x48/0x12c
> > >    l2cap_recv_frame+0x4770/0x6550
> > >    l2cap_recv_acldata+0x44c/0x7a4
> > >    hci_acldata_packet+0x100/0x188
> > >    hci_rx_work+0x178/0x23c
> > >    process_one_work+0x35c/0x95c
> > >    worker_thread+0x4cc/0x960
> > >    kthread+0x1a8/0x1c4
> > >    ret_from_fork+0x10/0x18
> > >
> > > Cc: stable@xxxxxxxxxx
> > > Cc: Marcel Holtmann <marcel@xxxxxxxxxxxx>
> > > Cc: Johan Hedberg <johan.hedberg@xxxxxxxxx>
> > > Cc: Luiz Augusto von Dentz <luiz.dentz@xxxxxxxxx>
> > > Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> > > Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> > > Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> > > Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> > > Cc: linux-bluetooth@xxxxxxxxxxxxxxx
> > > Cc: netdev@xxxxxxxxxxxxxxx
> > > Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
> > > ---
> > >  net/bluetooth/l2cap_core.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > No reply for 2 weeks.
> >
> > Is this patch being considered at all?
> >
> > Can I help in any way?
>
> Could you please resend to trigger CI, looks like CI missed this one
> for some reason.

Btw, it would be great to have a test for this sort of fix so CI
reproduce and thus we avoid reintroducing it:

https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/tools/l2cap-tester.c

>
> >
> > > diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
> > > index ae78490ecd3d4..82279c5919fd8 100644
> > > --- a/net/bluetooth/l2cap_core.c
> > > +++ b/net/bluetooth/l2cap_core.c
> > > @@ -483,9 +483,7 @@ static void l2cap_chan_destroy(struct kref *kref)
> > >
> > >       BT_DBG("chan %p", chan);
> > >
> > > -     write_lock(&chan_list_lock);
> > >       list_del(&chan->global_l);
> > > -     write_unlock(&chan_list_lock);
> > >
> > >       kfree(chan);
> > >  }
> > > @@ -501,7 +499,9 @@ void l2cap_chan_put(struct l2cap_chan *c)
> > >  {
> > >       BT_DBG("chan %p orig refcnt %u", c, kref_read(&c->kref));
> > >
> > > +     write_lock(&chan_list_lock);
> > >       kref_put(&c->kref, l2cap_chan_destroy);
> > > +     write_unlock(&chan_list_lock);
> > >  }
> > >  EXPORT_SYMBOL_GPL(l2cap_chan_put);
> > >
> >
> > --
> > Lee Jones [李琼斯]
> > Principal Technical Lead - Developer Services
> > Linaro.org │ Open source software for Arm SoCs
> > Follow Linaro: Facebook | Twitter | Blog
>
>
>
> --
> Luiz Augusto von Dentz



-- 
Luiz Augusto von Dentz