netdev - Re: [PATCH v1 net-next 02/14] net: Add a new socket option for a future transmit time.

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Message-ID: <c133ef6d-120c-52fb-e6bb-f33da5badb27@gmail.com>
Date:   Wed, 27 Jun 2018 15:16:59 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Jesus Sanchez-Palencia <jesus.sanchez-palencia@...el.com>,
        netdev@...r.kernel.org
Cc:     tglx@...utronix.de, jan.altenberg@...utronix.de,
        vinicius.gomes@...el.com, kurt.kanzenbach@...utronix.de,
        henrik@...tad.us, richardcochran@...il.com,
        levi.pearson@...man.com, ilias.apalodimas@...aro.org,
        ivan.khoronzhuk@...aro.org, mlichvar@...hat.com,
        willemb@...gle.com, jhs@...atatu.com, xiyou.wangcong@...il.com,
        jiri@...nulli.us, Richard Cochran <rcochran@...utronix.de>
Subject: Re: [PATCH v1 net-next 02/14] net: Add a new socket option for a
 future transmit time.



On 06/27/2018 02:59 PM, Jesus Sanchez-Palencia wrote:
> From: Richard Cochran <rcochran@...utronix.de>
> 
> This patch introduces SO_TXTIME. User space enables this option in
> order to pass a desired future transmit time in a CMSG when calling
> sendmsg(2). The argument to this socket option is a 6-bytes long struct
> defined as:
> 
> struct sock_txtime {
> 	clockid_t 	clockid;
> 	u16		flags;
> };

Note that sizeof(struct sock_txtime) is 8, not 6, because of alignments.

This means that your implementation of getsockopt(... SO_TXTIME )
is probably leaking two bytes of kernel stack to user space.