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

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Message-ID: <20100603124536.GW5483@bicker>
Date:	Thu, 3 Jun 2010 14:45:36 +0200
From:	Dan Carpenter <error27@...il.com>
To:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
Cc:	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 09:16:52PM +0900, Takuya Yoshikawa wrote:
> (2010/06/03 20:59), Jens Axboe wrote:
>> On 2010-06-03 12:35, Dan Carpenter wrote:
>>> copy_to_user() returns the number of bytes remaining, but we want to
>>> return -EFAULT.
>>> 	ret = fcntl(fd, F_SETOWN_EX, NULL);
>>> With the original code ret would be 8 here.
>>>
>>> V2: Takuya Yoshikawa pointed out a similar issue in f_getown_ex()
>>
>> Pretty basic bug, how long has this been there?
>
> IIUC, from the beginning, when these were introduced.
>
> And I recently sent similar bug fixes for other parts.
>

It was your clear_user() patch which inspired me.  I wrote a smatch
check to find these.  I've pushed the code to the smatch repo.
http://repo.or.cz/r/smatch.git

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.

regards,
dan carpenter


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