linux-kernel - Re: [PATCH 49/61] ISDN: fix drivers, by handling errors thrown by ->readstat()

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Message-ID: <45483887.3030702@garzik.org>
Date:	Wed, 01 Nov 2006 01:02:47 -0500
From:	Jeff Garzik <jeff@...zik.org>
To:	Chris Wright <chrisw@...s-sol.org>
CC:	linux-kernel@...r.kernel.org, stable@...nel.org,
	Justin Forbes <jmforbes@...uxtx.org>,
	Zwane Mwaikambo <zwane@....linux.org.uk>,
	Theodore Ts'o <tytso@....edu>,
	Randy Dunlap <rdunlap@...otime.net>,
	Dave Jones <davej@...hat.com>,
	Chuck Wolber <chuckw@...ntumlinux.com>,
	Chris Wedgwood <reviews@...cw.f00f.org>,
	Michael Krufky <mkrufky@...uxtv.org>, torvalds@...l.org,
	akpm@...l.org, alan@...rguk.ukuu.org.uk,
	Karsten Keil <kkeil@...e.de>
Subject: Re: [PATCH 49/61] ISDN: fix drivers, by handling errors thrown by
 ->readstat()

Chris Wright wrote:
> -stable review patch.  If anyone has any objections, please let us know.
> ------------------
> 
> From: Jeff Garzik <jeff@...zik.org>
> 
> This is a particularly ugly on-failure bug, possibly security, since the
> lack of error handling here is covering up another class of bug: failure to
> handle copy_to_user() return values.
> 
> The I4L API function ->readstat() returns an integer, and by looking at
> several existing driver implementations, it is clear that a negative return
> value was meant to indicate an error.
> 
> Given that several drivers already return a negative value indicating an
> errno-style error, the current code would blindly accept that [negative]
> value as a valid amount of bytes read.  Obvious damage ensues.
> 
> Correcting ->readstat() handling to properly notice errors fixes the
> existing code to work correctly on error, and enables future patches to
> more easily indicate errors during operation.
> 
> Signed-off-by: Jeff Garzik <jeff@...zik.org>
> Cc: Karsten Keil <kkeil@...e.de>
> Cc: <stable@...nel.org>
> Signed-off-by: Andrew Morton <akpm@...l.org>
> Signed-off-by: Linus Torvalds <torvalds@...l.org>
> Signed-off-by: Chris Wright <chrisw@...s-sol.org>

No objection, but I would think that you would also want the companion 
patch:

commit 7786ce192fc4917fb9b789dd823476ff8fd6cf66
Author: Jeff Garzik <jeff@...zik.org>
Date:   Tue Oct 17 00:10:40 2006 -0700

     [PATCH] ISDN: check for userspace copy faults

     Most of the ISDN ->readstat() implementations needed to check
     copy_to_user() and put_user() return values.


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