From mboxrd@z Thu Jan  1 00:00:00 1970
From: Michal Suchanek <hramrach@centrum.cz>
Subject: Re: [PATCH] tmpfs: implement generic xattr support
Date: Thu, 21 Apr 2011 08:59:54 +0200
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Cc: Phillip Lougher <phillip.lougher@gmail.com>,
	Andreas Dilger <adilger@dilger.ca>,
	Jiri Kosina <jkosina@suse.cz>,
	Ric Wheeler <ricwheeler@gmail.com>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	David Howells <dhowells@redhat.com>,
	Ian Kent <ikent@redhat.com>, Jeff Moyer <jmoyer@redhat.com>,
	Christoph Hellwig <hch@infradead.org>,
	Hugh Dickins <hughd@google.com>, Eric Paris <eparis@redhat.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <87tydtm41s.fsf@tucsk.pomaz.szeredi.hu>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: linux-fsdevel.vger.kernel.org

On 20 April 2011 15:43, Miklos Szeredi <miklos@szeredi.hu> wrote:
> Phillip Lougher <phillip.lougher@gmail.com> writes:
>
>> On Tue, Apr 19, 2011 at 9:04 PM, Miklos Szeredi <miklos@szeredi.hu> =
wrote:
>>
>>> +static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer=
, size_t size)
>>
>>> + =C2=A0 =C2=A0 =C2=A0 spin_lock(&dentry->d_inode->i_lock);
>>> + =C2=A0 =C2=A0 =C2=A0 list_for_each_entry(xattr, &info->xattr_list=
, list) {
>>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 /* skip "trusted=
=2E" attributes for unprivileged callers */
>>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 if (!trusted && =
xattr_is_trusted(xattr->name))
>>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 continue;
>>> +
>>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 used +=3D strlen=
(xattr->name) + 1;
>>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 if (buffer) {
>>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 if (size < used) {
>>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 used =3D -ERANGE;
>>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 break;
>>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 }
>>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 strncpy(buffer, xattr->name, strlen(xattr->name) + 1);
>>>+ =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0buffer +=3D strlen(xattr->name) + 1;
>>
>> Why are you doing a strncpy here? =C2=A0strcpy() isn't going to copy=
 more
>> than strlen(xattr->name) + 1 bytes, and you know buffer is large
>> enough to hold that because of the previous if (size < used) check?
>>
>> If you assigned the first strlen(xattr->name) + 1 to a temporary
>> variable, you could use memcpy here, and avoid the 3 repeated
>> strlen(xattr->name) calls.
>
> Yeah, makes sense.
>

Can you put up a branch with both overlayfs and xattrs?

I would like to point people at a repo with working implementation and
mirroring the kernel tree to add one patch is a bit overkill.

Thanks

Michal