Re: [PATCH] Bluetooth: Fix kernel crash on BT stress tests.

["Gustavo F. Padovan" <padovan@profusion.mobi>]

Hi Andrei,

* Andrei Emeltchenko <andrei.emeltchenko.news@gmail.com> [2010-02-16 13:58:34 +0200]:

> On Tue, Feb 16, 2010 at 1:34 PM, Gustavo F. Padovan
> <padovan@profusion.mobi> wrote:
> > Hi Andrei,
> >
> > * Andrei Emeltchenko <andrei.emeltchenko.news@gmail.com> [2010-02-16 12:36:47 +0200]:
> >
> >> From 0135f732cb45e5e91062aca84a61a40b172200a4 Mon Sep 17 00:00:00 2001
> >> From: Andrei Emeltchenko <andrei.emeltchenko@nokia.com>
> >> Date: Tue, 16 Feb 2010 10:52:33 +0200
> >> Subject: [PATCH] Bluetooth: Fix kernel crash on BT stress tests.
> >>
> >> Added very simple check that req buffer has enough space to
> >> fit configuration parameters. Shall be enough to reject packets
> >> with configuration size more than req buffer.
> >>
> >> Crash trace below
> >>
> >> [ 6069.659393] Unable to handle kernel paging request at virtual
> >> address 02000205
> >> [ 6069.673034] Internal error: Oops: 805 [#1] PREEMPT
> >> ...
> >> [ 6069.727172] PC is at l2cap_add_conf_opt+0x70/0xf0 [l2cap]
> >> [ 6069.732604] LR is at l2cap_recv_frame+0x1350/0x2e78 [l2cap]
> >> ...
> >> [ 6070.030303] Backtrace:
> >> [ 6070.032806] [<bf1c2880>] (l2cap_add_conf_opt+0x0/0xf0 [l2cap]) from
> >> [<bf1c6624>] (l2cap_recv_frame+0x1350/0x2e78 [l2cap])
> >> [ 6070.043823]  r8:dc5d3100 r7:df2a91d6 r6:00000001 r5:df2a8000 r4:00000200
> >> [ 6070.050659] [<bf1c52d4>] (l2cap_recv_frame+0x0/0x2e78 [l2cap]) from
> >> [<bf1c8408>] (l2cap_recv_acldata+0x2bc/0x350 [l2cap])
> >> [ 6070.061798] [<bf1c814c>] (l2cap_recv_acldata+0x0/0x350 [l2cap]) from
> >> [<bf0037a4>] (hci_rx_task+0x244/0x478 [bluetooth])
> >> [ 6070.072631]  r6:dc647700 r5:00000001 r4:df2ab740
> >> [ 6070.077362] [<bf003560>] (hci_rx_task+0x0/0x478 [bluetooth]) from
> >> [<c006b9fc>] (tasklet_action+0x78/0xd8)
> >> [ 6070.087005] [<c006b984>] (tasklet_action+0x0/0xd8) from [<c006c160>]
> >
> > Are you using ERTM or Streaming mode? If yes, I have a guess about the
> > source of the problem. On l2cap_parse_conf_rsp we check for:
> >
> >        while (len >= L2CAP_CONF_OPT_SIZE) {
> >                len -= l2cap_get_conf_opt(&rsp, &type, &olen, &val);
> >
> > But on case L2CAP_CONF_RFC olen is greater than L2CAP_CONF_OPT_SIZE we
> > can exceed the buffer size. So the right fix will be check if len >=
> > olen in that case.
> 
> We use test tool which sends "Configure Response" packet with size 262
> bytes. So "req" buffer gets overwritten. But in the code nobody checks
> that "req" might be overwritten.

So I have found another issue. ;)
Have to fix it.

> 
> -- Andrei
> 
> >
> >
> >>
> >> Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@nokia.com>
> >> ---
> >>  net/bluetooth/l2cap.c |    6 ++++++
> >>  1 files changed, 6 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
> >> index 400efa2..69b7280 100644
> >> --- a/net/bluetooth/l2cap.c
> >> +++ b/net/bluetooth/l2cap.c
> >> @@ -2830,6 +2830,12 @@ static inline int l2cap_config_rsp(struct
> >> l2cap_conn *conn, struct l2cap_cmd_hdr
> >>                       int len = cmd->len - sizeof(*rsp);
> >>                       char req[64];
> >>
> >> +                     if (len > sizeof(req) - sizeof(struct l2cap_conf_req)) {
> >> +                             BT_ERR("Config response is too big");
> >> +                             l2cap_send_disconn_req(conn, sk);
> >> +                             goto done;
> >> +                     }
> >> +
> >>                       /* throw out any old stored conf requests */
> >>                       result = L2CAP_CONF_SUCCESS;
> >>                       len = l2cap_parse_conf_rsp(sk, rsp->data,
> >> --
> >> 1.6.0.4
> >
> >
> > --
> > Gustavo F. Padovan
> > http://padovan.org
> >
> > ProFUSION embedded systems - http://profusion.mobi
> >
> --
> To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

-- 
Gustavo F. Padovan
http://padovan.org

ProFUSION embedded systems - http://profusion.mobi