Hi Nathan,
* Nathan Holstein <nathan.holstein@xxxxxxxxx> [2010-10-14 18:37:53 -0400]:
> (Please keep me in the CC list, I'm not subscribed to lkml)
>
> [1] L2CAP module dereferences an uninitialized pointer within l2cap_connect_req.
>
> [2] I'm currently testing a 2.6.35 kernel on a Nexus One with backported
> patches from bluetooth-2.6. When testing against certain BT devices, I'm seeing
> a null-pointer deref. The crash is caused by this portion of commit e9aeb2dd:
>
> @@ -2966,6 +2991,15 @@ sendresp:
> L2CAP_INFO_REQ, sizeof(info), &info);
> }
>
> + if (!(l2cap_pi(sk)->conf_state & L2CAP_CONF_REQ_SENT) &&
> + result == L2CAP_CR_SUCCESS) {
> + u8 buf[128];
> + l2cap_pi(sk)->conf_state |= L2CAP_CONF_REQ_SENT;
> + l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
> + l2cap_build_conf_req(sk, buf), buf);
> + l2cap_pi(sk)->num_conf_req++;
> + }
> +
> return 0;
> }
>
> Multiple error cases jump to the response & sendresp labels prior to
> initializing
> the "sk" variable. In the case I'm currently seeing, the remote BT
> device fails to
> properly secure the ACL, making this crash 100% reproducible.
>
> [3] Bluetooth, L2CAP
>
> [4] This bug appears to be in the mainline 2.6.36-rc? kernel, in addition to
> multiple Bluetooth development trees
>
> The following patch fixes the crash.
>
>
> --nathan
>
> ---
> In error cases when the ACL is insecure or we fail to allocate a new
> struct sock, we jump to the "response" label. If so, "sk" will be
> uninitialized and the kernel crashes.
>
> Signed-off-by: Nathan Holstein <nathan.holstein@xxxxxxxxx>
> ---
> net/bluetooth/l2cap.c | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
> index d527b10..10ae0af 100644
> --- a/net/bluetooth/l2cap.c
> +++ b/net/bluetooth/l2cap.c
> @@ -2911,7 +2911,7 @@ static inline int l2cap_connect_req(struct
> l2cap_conn *conn, struct l2cap_cmd_hd
> struct l2cap_chan_list *list = &conn->chan_list;
> struct l2cap_conn_req *req = (struct l2cap_conn_req *) data;
> struct l2cap_conn_rsp rsp;
> - struct sock *parent, *uninitialized_var(sk);
> + struct sock *parent, *sk = 0;
Your fix is right, but please make *sk = NULL here.
When I wrote that code I thought is was a false positive, but no, it's
bug. :(
--
Gustavo F. Padovan
ProFUSION embedded systems - http://profusion.mobi
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