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

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Message-Id: <39E6B251-4ED3-4C0F-B8A2-0FAAF6E905A6@holtmann.org>
Date:   Fri, 18 Jan 2019 10:37:25 +0100
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Johan Hedberg <johan.hedberg@...il.com>,
        linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org,
        Ran Menscher <ran.menscher@...ambasecurity.com>
Subject: Re: [PATCH 2/2] Bluetooth: check the buffer size for some messages
 before parsing

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.menscher@...ambasecurity.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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