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

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Date:	Thu, 03 Jun 2010 14:38:03 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
Cc:	Jens Axboe <jaxboe@...ionio.com>,
	Dan Carpenter <error27@...il.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

Le jeudi 03 juin 2010 à 21:16 +0900, Takuya Yoshikawa a écrit :
> (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.

Maybe copy_to_user() was changed sometime to return a partial count
instead of EFAULT ?

I do think we should have a set of helper functions, instead of
spreading special EFAULT cases in one housand places...

This is really ugly.

static inline int sec_copy_to_user(arg1, arg2, arg3)
{
	int res = copy_to_user(arg1, arg2, arg3);

	return (res > 0) ? -EFAULT : res;
}



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