netdev - Re: [PATCH net-next] sock: ignore TIMESTAMP, RXQ_OVFL, WIFI_STATUS in sock_cmsg

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Date:	Fri, 13 May 2016 08:14:22 -0400
From:	Soheil Hassas Yeganeh <soheil@...gle.com>
To:	David Miller <davem@...emloft.net>
Cc:	Soheil Hassas Yeganeh <soheil.kdev@...il.com>,
	netdev <netdev@...r.kernel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Maciej Żenczykowski <maze@...gle.com>,
	Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net-next] sock: ignore TIMESTAMP, RXQ_OVFL, WIFI_STATUS in sock_cmsg_send

On Fri, May 13, 2016 at 2:03 AM, David Miller <davem@...emloft.net> wrote:
> From: Soheil Hassas Yeganeh <soheil.kdev@...il.com>
> Date: Fri, 13 May 2016 00:47:10 -0400
>
>> From: Soheil Hassas Yeganeh <soheil@...gle.com>
>>
>> SO_TIMESTAMP(NS), RXQ_OVFL, and WIFI_STATUS can be returned as
>> receive-side control messages from recvmsg(). Although invalid,
>> some applications may reflect those receive-side control messages
>> back to sendmsg(). Since socket-level control messages were being
>> ignored in ipv4 and ipv6, such applications would not get an error.
>>
>> 24025c4 (ipv4: process socket-level control messages in IPv4) and
>> ad1e46 (ipv6: process socket-level control messages in IPv6) add
>> support for socket-level control messages in ipv4 and ipv6 on
>> sendmsg(). This results in getting -EINVAL, if the application
>> passes in a message with SO_WIFI_STATUS, SO_RXQ_OVFL, SO_TIMESTAMP
>> and/or SO_TIMESTAMPNS that might have been received in recvmsg().
>>
>> Ignore SO_WIFI_STATUS, SO_TIMESTAMP(NS), and SO_RXQ_OVFL when
>> processing socket-level control messages in send-side to remain
>> backward compatible.
>
> This patch is missing a proper Signed-Off-By: tag.

Oops, sorry. :(

> But I think this change is wrong.  Just because we silently accepted
> garbage in the past doesn't mean more strict checking is invalid.
>
> Applications blindly echoing control messages from recvmsg to sendmsg
> must be fixed.

Agreed, by this patch, I just wanted to note such potential issues and
make sure I haven't broken any user-space application. Thanks David!