Re: [PATCH 2/2] Bluetooth: check the buffer size for some messages before parsing

[Marcel Holtmann]

Hi Greg,

> The L2CAP_CONF_EFS and L2CAP_CONF_RFC messages can be sent from
> userspace so their structure sizes need to be checked before parsing
> them.

this message is confusing me. How can these be send from userspace?

> 
> Based on a patch from Ran Menscher.
> 
> Reported-by: Ran Menscher <ran.mensc...@karambasecurity.com>
> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
> ---
> net/bluetooth/l2cap_core.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
> index 93daf94565cf..55e48e6efc2b 100644
> --- a/net/bluetooth/l2cap_core.c
> +++ b/net/bluetooth/l2cap_core.c
> @@ -3361,7 +3361,8 @@ static int l2cap_parse_conf_req(struct l2cap_chan 
> *chan, void *data, size_t data
>                       break;
> 
>               case L2CAP_CONF_RFC:
> -                     if (olen == sizeof(rfc))
> +                     if ((olen == sizeof(rfc)) &&
> +                         (endptr - ptr >= L2CAP_CONF_OPT_SIZE + sizeof(rfc)))
>                               memcpy(&rfc, (void *) val, olen);

We don’t do ((x == y) && (..)) actually. Using (x == y && ..) is plenty.

>                       break;
> 
> @@ -3371,7 +3372,8 @@ static int l2cap_parse_conf_req(struct l2cap_chan 
> *chan, void *data, size_t data
>                       break;
> 
>               case L2CAP_CONF_EFS:
> -                     if (olen == sizeof(efs)) {
> +                     if ((olen == sizeof(efs)) &&
> +                         (endptr - ptr >= L2CAP_CONF_OPT_SIZE + 
> sizeof(efs))) {
>                               remote_efs = 1;
>                               memcpy(&efs, (void *) val, olen);
>                       }
> @@ -3576,7 +3578,8 @@ static int l2cap_parse_conf_rsp(struct l2cap_chan 
> *chan, void *rsp, int len,
>                       break;
> 
>               case L2CAP_CONF_RFC:
> -                     if (olen == sizeof(rfc))
> +                     if ((olen == sizeof(rfc)) &&
> +                         (endptr - ptr >= L2CAP_CONF_OPT_SIZE + sizeof(rfc)))
>                               memcpy(&rfc, (void *)val, olen);
> 
>                       if (test_bit(CONF_STATE2_DEVICE, &chan->conf_state) &&
> @@ -3596,7 +3599,8 @@ static int l2cap_parse_conf_rsp(struct l2cap_chan 
> *chan, void *rsp, int len,
>                       break;
> 
>               case L2CAP_CONF_EFS:
> -                     if (olen == sizeof(efs)) {
> +                     if ((olen == sizeof(efs)) &&
> +                         (endptr - ptr >= L2CAP_CONF_OPT_SIZE + 
> sizeof(efs))) {
>                               memcpy(&efs, (void *)val, olen);
> 
>                               if (chan->local_stype != L2CAP_SERV_NOTRAFIC &&

Regards

Marcel