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

[Andrei Emeltchenko <andrei.emeltchenko.news@gmail.com>]

Hi Gustavo

On Thu, Feb 18, 2010 at 1:57 AM, Gustavo F. Padovan
<padovan@profusion.mobi> wrote:
> 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.

Is len always bigger then olen?

in  l2cap_get_conf_opt :

len = L2CAP_CONF_OPT_SIZE + opt->len;

opt->len is olen

-- Andrei

>>
>> 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
>