linux-kernel - Re: [PATCH 28/49] tty: Add a new file /proc/tty/consoles

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Date:	Sat, 23 Oct 2010 13:26:12 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	Greg Kroah-Hartman <gregkh@...e.de>, linux-kernel@...r.kernel.org,
	"Dr. Werner Fink" <werner@...e.de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 28/49] tty: Add a new file /proc/tty/consoles

On Sat, Oct 23, 2010 at 02:00:38PM +0200, Jiri Slaby wrote:

> > Please, don't.  Even leaving aside the fact that it's mind-bogglingly
> > broken (->private_data can be _ANYTHING_, including arbitrary number cast
> > to pointer), you really shouldn't screw your way through the descriptor
> > table in the first place.
> > 
> > Strongly NACKed.
> 
> Well, our complains are -ETOOLATE -- it's commit f4a3e0bceb57466c
> upstream. So please fix this up.

FVO "fix" equal to "revert".  Belated review:

a) global variable depending on stdin of the last opener?  Affecting
output of read(2)?  Really?

b) iterator is broken; list should be locked in ->start(), unlocked
in ->stop() and *NOT* unlocked/relocked in ->next()

c) ->show() ought to do nothing in case of ->device == NULL, instead
of skipping those in ->next()/->start()

d) regardless of the merits of the bright idea about asterisk at that
line in output *and* regardless of (a), the implementation is not only
atrociously ugly, it's actually very likely to be a roothole.  Verifying
that Cthulhu knows what number happens to be address of a tty_struct by
blindly dereferencing memory at that address...  Ouch.

Please revert that crap.
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