linux-kernel - Re: compat: autofs v5 packet size ambiguity

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Message-ID: <4F4529D4.6070008@zytor.com>
Date:	Wed, 22 Feb 2012 09:45:56 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Ian Kent <raven@...maw.net>, David Miller <davem@...emloft.net>,
	linux-kernel@...r.kernel.org, autofs@...r.kernel.org,
	Thomas Meyer <thomas@...3r.de>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: compat: autofs v5 packet size ambiguity - update

On 02/22/2012 08:10 AM, Linus Torvalds wrote:
> 
> But yeah, writing fixed-size data and then having a reader that reads
> fixed-size data is just not a very good approach. It's doubly bad when
> the "fixed size" isn't an explicit size that is documented in the
> protocol, but depends on data structures.
> 

Incidentally, a valid user space workaround for this problem would be to
just read all the data off the pipe but consider the packet length to be
NAME_MAX rather than NAME_MAX+1; then simply discard all-zero ints
received on input since a packet always starts with the autofs version
number.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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