From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joe Perches <joe@perches.com>
Subject: Re: [patch] isdn: fix a wrapping bug in isdn_ppp_ioctl()
Date: Wed, 10 Oct 2012 08:52:22 -0700
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Cc: Andreas Schwab <schwab@linux-m68k.org>,
	Dan Carpenter <dan.carpenter@oracle.com>,
	Karsten Keil <isdn@linux-pingi.de>,
	"David S. Miller" <davem@davemloft.net>,
	Masanari Iida <standby24x7@gmail.com>, netdev@vger.kernel.org,
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To: David Laight <David.Laight@ACULAB.COM>
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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?