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

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Date:	Thu, 03 Jun 2010 12:42:14 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Dan Carpenter <error27@...il.com>
Cc:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>,
	Matthew Wilcox <matthew@....cx>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch v2] fcntl: return -EFAULT if copy_to_user fails

On Thu, 2010-06-03 at 12:35 +0200, 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()
> 
> Signed-off-by: Dan Carpenter <error27@...il.com>

Acked-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>

> diff --git a/fs/fcntl.c b/fs/fcntl.c
> index f74d270..51e11bf 100644
> --- a/fs/fcntl.c
> +++ b/fs/fcntl.c
> @@ -274,7 +274,7 @@ static int f_setown_ex(struct file *filp, unsigned long arg)
>  
>  	ret = copy_from_user(&owner, owner_p, sizeof(owner));
>  	if (ret)
> -		return ret;
> +		return -EFAULT;
>  
>  	switch (owner.type) {
>  	case F_OWNER_TID:
> @@ -332,8 +332,11 @@ static int f_getown_ex(struct file *filp, unsigned long arg)
>  	}
>  	read_unlock(&filp->f_owner.lock);
>  
> -	if (!ret)
> +	if (!ret) {
>  		ret = copy_to_user(owner_p, &owner, sizeof(owner));
> +		if (ret)
> +			ret = -EFAULT;
> +	}
>  	return ret;
>  }
>  

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