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 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>]
> 
> 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");

Remove the BT_ERR, normally we don't print any error on
l2cap_send_disconn_req.


> +				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,

Also, this is very rare crash. Even if we add all configure options to
req we won't overwrite it. Doesn't make sense to me send a
configuration option more than once in the same config_{rsp,req}. The
only way to crash l2cap is using a bugous remote stack or a stress test
tools. We need to be protected against those bugous stacks so I'll
ack your patch after you send the updated patch without the BT_ERR.


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

ProFUSION embedded systems - http://profusion.mobi