linux-kernel - Re: [patch v2] fcntl: return -EFAULT if copy_to

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Date:	Fri, 4 Jun 2010 13:14:26 +0200
From:	Dan Carpenter <error27@...il.com>
To:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>,
	Jens Axboe <jaxboe@...ionio.com>,
	Matthew Wilcox <matthew@....cx>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch v2] fcntl: return -EFAULT if copy_to_user fails

On Thu, Jun 03, 2010 at 02:45:36PM +0200, Dan Carpenter wrote:
> The heuristic I use is that if we return a variable which is the 
> return value of copy_to_user() and it's non-zero then complain.  It 
> didn't find the f_getown_ex() because that return value could come from
> copy_to_user() or it could be -EINVAL.
> 
> I'll mess with it a bit and see if I can make it catch the f_getown_ex()
> bug.
> 

I changed the heuristic to complain if we return a non-zero return from
copy_to_user() and the minimum possible value of the return is not zero.

	ret = copy_to_user();
	if (ret)
		return ret;  // <- Complain.  The minimum value is 1.

Or:

	if (!foo)
		ret = -ENOMEM;
	if (!ret)
		ret = copy_to_user();
	return ret;  // <- Complain.  The minimum value is -ENOMEM.

This seems to work pretty well.  I've fixed all the bugs this found and 
I've pushed the check to the smatch repo.

regards,
dan carpenter
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