> On Wed, Jan 10, 2018 at 06:20:41PM +0100, Lorenzo Bianconi wrote:
>> Set l2specific_len according to the L2-Specific Sublayer type specified
>> by the userspace and not rely on a user supplied value for sublayer len
>> since invalid usage of L2TP_ATTR_L2SPEC_LEN allows leaking memory on the
>> network and sending corrupted frames.
>> Moreover add a sanity check on l2specific_type provided by userspace
>>
>> Signed-off-by: Lorenzo Bianconi <lorenzo.bianc...@redhat.com>
>> ---
>> net/l2tp/l2tp_netlink.c | 21 ++++++++++++++++-----
>> 1 file changed, 16 insertions(+), 5 deletions(-)
>>
>> diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
>> index 48b5bf30ec50..404e5482c4e7 100644
>> --- a/net/l2tp/l2tp_netlink.c
>> +++ b/net/l2tp/l2tp_netlink.c
>> @@ -550,13 +550,24 @@ static int l2tp_nl_cmd_session_create(struct sk_buff
>> *skb, struct genl_info *inf
>> if (info->attrs[L2TP_ATTR_DATA_SEQ])
>> cfg.data_seq =
>> nla_get_u8(info->attrs[L2TP_ATTR_DATA_SEQ]);
>>
>> - cfg.l2specific_type = L2TP_L2SPECTYPE_DEFAULT;
>> - if (info->attrs[L2TP_ATTR_L2SPEC_TYPE])
>> + if (info->attrs[L2TP_ATTR_L2SPEC_TYPE]) {
>> cfg.l2specific_type =
>> nla_get_u8(info->attrs[L2TP_ATTR_L2SPEC_TYPE]);
>>
>> - cfg.l2specific_len = 4;
>> - if (info->attrs[L2TP_ATTR_L2SPEC_LEN])
>> - cfg.l2specific_len =
>> nla_get_u8(info->attrs[L2TP_ATTR_L2SPEC_LEN]);
>> + switch (cfg.l2specific_type) {
>> + case L2TP_L2SPECTYPE_DEFAULT:
>> + cfg.l2specific_len = 4;
>> + break;
>> + case L2TP_L2SPECTYPE_NONE:
>> + cfg.l2specific_len = 0;
>> + break;
>> + default:
>> + ret = -EINVAL;
>> + goto out_tunnel;
>> + }
>> + } else {
>> + cfg.l2specific_type = L2TP_L2SPECTYPE_DEFAULT;
>> + cfg.l2specific_len = 4;
>> + }
>>
>> if (info->attrs[L2TP_ATTR_COOKIE]) {
>> u16 len = nla_len(info->attrs[L2TP_ATTR_COOKIE]);
>>
> I think we can go one step further and remove .l2specific_len from
> struct l2tp_session and struct l2tp_session_cfg. We never need this
> information. Then we can start ignoring the L2TP_ATTR_L2SPEC_LEN
> attribute just like we've done with L2TP_ATTR_OFFSET.
Hi Guillaume,
I was thinking about it, let's way for some feedbacks and then I can
respin a v2.
Regards,
Lorenzo
