netdev - Re: [PATCH 1/2] Bluetooth: check message types in l2cap_get_conf

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Date:   Thu, 10 Jan 2019 13:02:09 -0800
From:   Joe Perches <joe@...ches.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>
Cc:     linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 1/2] Bluetooth: check message types in l2cap_get_conf_opt

On Thu, 2019-01-10 at 07:28 +0100, Greg Kroah-Hartman wrote:
> l2cap_get_conf_opt can handle a "default" message type, but it needs to
> be verified that it really is the correct type (CONF_EFS or CONF_RFC)
> before passing it back to the caller.  To do this we need to check the
> return value of this call now and handle the error correctly up the
> stack.
[]
> diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
[]
> @@ -3324,7 +3328,7 @@ static int l2cap_parse_conf_req(struct l2cap_chan *chan, void *data, size_t data
>  	void *endptr = data + data_size;
>  	void *req = chan->conf_req;
>  	int len = chan->conf_len;
> -	int type, hint, olen;
> +	int type, hint, olen, err;

err doesn't seem the right name for any of these as the
return is now negative only when there is an error.

Maybe opt_len instead.

>  	unsigned long val;
>  	struct l2cap_conf_rfc rfc = { .mode = L2CAP_MODE_BASIC };
>  	struct l2cap_conf_efs efs;
> @@ -3336,7 +3340,10 @@ static int l2cap_parse_conf_req(struct l2cap_chan *chan, void *data, size_t data
>  	BT_DBG("chan %p", chan);
>  
>  	while (len >= L2CAP_CONF_OPT_SIZE) {
> -		len -= l2cap_get_conf_opt(&req, &type, &olen, &val);
> +		err = l2cap_get_conf_opt(&req, &type, &olen, &val);
> +		if (err < 0)
> +			return err;
> +		len -= err;

especially as you subtract the positive return not
an error value.

>  
>  		hint  = type & L2CAP_CONF_HINT;
>  		type &= L2CAP_CONF_MASK;
> @@ -3539,7 +3546,7 @@ static int l2cap_parse_conf_rsp(struct l2cap_chan *chan, void *rsp, int len,
>  	struct l2cap_conf_req *req = data;
>  	void *ptr = req->data;
>  	void *endptr = data + size;
> -	int type, olen;
> +	int type, olen, err;
>  	unsigned long val;
>  	struct l2cap_conf_rfc rfc = { .mode = L2CAP_MODE_BASIC };
>  	struct l2cap_conf_efs efs;
> @@ -3547,7 +3554,10 @@ static int l2cap_parse_conf_rsp(struct l2cap_chan *chan, void *rsp, int len,
>  	BT_DBG("chan %p, rsp %p, len %d, req %p", chan, rsp, len, data);
>  
>  	while (len >= L2CAP_CONF_OPT_SIZE) {
> -		len -= l2cap_get_conf_opt(&rsp, &type, &olen, &val);
> +		err = l2cap_get_conf_opt(&rsp, &type, &olen, &val);
> +		if (err < 0)
> +			return err;
> +		len -= err;
>  
>  		switch (type) {
>  		case L2CAP_CONF_MTU:
> @@ -3707,7 +3717,7 @@ void __l2cap_connect_rsp_defer(struct l2cap_chan *chan)
>  
>  static void l2cap_conf_rfc_get(struct l2cap_chan *chan, void *rsp, int len)
>  {
> -	int type, olen;
> +	int type, olen, err;
>  	unsigned long val;
>  	/* Use sane default values in case a misbehaving remote device
>  	 * did not send an RFC or extended window size option.
> @@ -3727,7 +3737,10 @@ static void l2cap_conf_rfc_get(struct l2cap_chan *chan, void *rsp, int len)
>  		return;
>  
>  	while (len >= L2CAP_CONF_OPT_SIZE) {
> -		len -= l2cap_get_conf_opt(&rsp, &type, &olen, &val);
> +		err = l2cap_get_conf_opt(&rsp, &type, &olen, &val);
> +		if (err < 0)
> +			return;
> +		len -= err;
>  
>  		switch (type) {
>  		case L2CAP_CONF_RFC: