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Date: Tue, 18 Feb 2014 15:16:50 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Fabian Frederick <fabf@skynet.be>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] fs: xattr: Don't display attributes without read
 access
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On Sun, 16 Feb 2014 20:31:01 +0800 Fabian Frederick <fabf@skynet.be> wrote:

> Any user can display extented attribute names without read
> access.
> 
> eg: attr -l <filename>
> 
> This patch checks inode_permission in listxattr common
> function before executing vfs_listxattr.
> 
> ...
>
> --- a/fs/xattr.c
> +++ b/fs/xattr.c
> @@ -543,6 +543,10 @@ listxattr(struct dentry *d, char __user *list, size_t size)
>  	char *klist = NULL;
>  	char *vlist = NULL;	/* If non-NULL, we used vmalloc() */
>  
> +	error = inode_permission(d->d_inode, MAY_READ);
> +	if (error)
> +		return error;
> +
>  	if (size) {
>  		if (size > XATTR_LIST_MAX)
>  			size = XATTR_LIST_MAX;

erk.  Doesn't this mean that if existing userspace is relying on the
current behaviour, this patch will cause breakage?