linux-kernel - Re: [PATCH] fs: change sys_truncate/sys

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Date:	Wed, 23 Sep 2009 08:13:47 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@....de>,
	Al Viro <viro@...iv.linux.org.uk>,
	"H. Peter Anvin" <hpa@...or.com>, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs: change sys_truncate/sys_ftruncate length parameter
 type

On Wed, 23 Sep 2009, Heiko Carstens wrote:
> 
> For both system calls user space passes a signed long length parameter,
> while the kernel side takes an unsigned long parameter and converts it
> later to signed long again.

No it doesn't.

Look at sys_ftruncate() again. It doesn't convert it to signed long at 
all. It converts it to 'loff_t' which is something different entirely.

Now, it may be that we _should_ convert it to 'long' like your patch does, 
but this is definitely not a "no changes" patch as far as I can tell. It 
limits ftruncate to 31 bits on 32-bit architectures, in ways it didn't use 
to be limited.

[ Note the "small" logic and the interaction with O_LARGEFILE. On a 32-bit 
  architecture, if you open with O_LARGEFILE, ftruncate() gets the full 
  32-bit range, and that's the part your patch broke. ]

So NAK. Not without some serious explanations on why I'm wrong and am just 
being unnecessarily difficult and a pinhead.

			Linus
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