netdev - Re: [patch] isdn: fix a wrapping bug in isdn_ppp

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Date:	Wed, 10 Oct 2012 08:52:22 -0700
From:	Joe Perches <joe@...ches.com>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	Andreas Schwab <schwab@...ux-m68k.org>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Karsten Keil <isdn@...ux-pingi.de>,
	"David S. Miller" <davem@...emloft.net>,
	Masanari Iida <standby24x7@...il.com>, netdev@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [patch] isdn: fix a wrapping bug in isdn_ppp_ioctl()

On Wed, 2012-10-10 at 16:44 +0100, David Laight wrote:
> > On Wed, 2012-10-10 at 15:59 +0100, David Laight wrote:
> > > Seems to me the code is expecting 256 bits of data, not any multiple of int,
> > > long or anything else.
> > 
> > include/linux/isdn_ppp.h:#define PPPIOCGCOMPRESSORS _IOR('t',134,unsigned long [8])
> 
> That doesn't mean the whole thing makes any sense on 64bit systems.
> A whole load of historic code used 'long' to ensure 32bit.
> Some of that might have crept into Linux sources.

Very true, but it's exported via copy_to_user.

> Since I suspect there are a maximum of 256 bits on both 32 and 64bit
> systems, I wouldn't like to guess exactly how any particular 64bit
> application chooses to check the bitmap.
> 
> The ioctl constant may be wrong on 64 bit systems.

shrug.  Not much to do about it now.
isdn isn't very active.

Karsten?  What do you think?

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