From: Steve Rago <sar@nec-labs.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Network Development <netdev@vger.kernel.org>,
David Miller <davem@davemloft.net>,
Michael Kerrisk-manpages <mtk.manpages@gmail.com>,
Eric Biederman <ebiederm@xmission.com>
Subject: Re: bug in passing file descriptors
Date: Mon, 7 Oct 2013 15:06:02 -0400 [thread overview]
Message-ID: <5253061A.7060701@nec-labs.com> (raw)
In-Reply-To: <CALCETrXmmW-nRTr4-yWJnNr2GWW37KW-7B1m=kSRnmYjhMTajA@mail.gmail.com>
On 10/07/2013 02:44 PM, Andy Lutomirski wrote:
>
> ISTM that, in order for further cmsgs to be correctly decoded, all of
> the relevant things need to match.
>
> put_cmsg uses this layout: cmsghdr, padding, payload, padding.
> CMSG_SPACE matches that calculation.
>
> scm_detach_fds is the actual code path for SCM_RIGHTS. It does the same thing.
>
> CMSG_DATA also things that there's possible padding after cmsghdr.
>
> So I think everything's okay.
>
> --Andy
>
Maybe. So a client expecting to receive x bytes of control information should make sure their buffer is at least
CMSG_SPACE(x) bytes long instead of CMSG_LEN(x) bytes long, because you feel compelled to copy the final padding from
kernel space to user space? Seems wrong to me. IMHO, the final padding should only come into play when calculating
where the next header should begin.
Steve
next prev parent reply other threads:[~2013-10-07 19:06 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-07 18:27 bug in passing file descriptors Steve Rago
2013-10-07 18:44 ` Andy Lutomirski
2013-10-07 19:06 ` Steve Rago [this message]
2013-10-07 19:12 ` David Miller
2013-10-07 19:17 ` Steve Rago
2013-10-07 19:42 ` David Miller
2013-10-07 20:29 ` Steve Rago
2013-10-07 21:32 ` David Miller
2013-10-07 22:55 ` Andi Kleen
2013-10-08 14:32 ` Steve Rago
2013-10-08 16:02 ` Andy Lutomirski
2013-10-08 16:18 ` Steve Rago
2013-10-08 16:41 ` Andi Kleen
2013-10-08 16:51 ` Steve Rago
2013-10-09 14:07 ` Steve Rago
2013-10-08 8:43 ` David Laight
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