linux-kernel - Re: [PATCH] tmpfs: implement generic xattr support

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Message-ID: <BANLkTikJ_7ZZ+1uC=0RBmKmxqFhVyLiYsw@mail.gmail.com>
Date:	Thu, 21 Apr 2011 08:59:54 +0200
From:	Michal Suchanek <hramrach@...trum.cz>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	Phillip Lougher <phillip.lougher@...il.com>,
	Andreas Dilger <adilger@...ger.ca>,
	Jiri Kosina <jkosina@...e.cz>,
	Ric Wheeler <ricwheeler@...il.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	David Howells <dhowells@...hat.com>,
	Ian Kent <ikent@...hat.com>, Jeff Moyer <jmoyer@...hat.com>,
	Christoph Hellwig <hch@...radead.org>,
	Hugh Dickins <hughd@...gle.com>, Eric Paris <eparis@...hat.com>
Subject: Re: [PATCH] tmpfs: implement generic xattr support

On 20 April 2011 15:43, Miklos Szeredi <miklos@...redi.hu> wrote:
> Phillip Lougher <phillip.lougher@...il.com> writes:
>
>> On Tue, Apr 19, 2011 at 9:04 PM, Miklos Szeredi <miklos@...redi.hu> wrote:
>>
>>> +static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
>>
>>> +       spin_lock(&dentry->d_inode->i_lock);
>>> +       list_for_each_entry(xattr, &info->xattr_list, list) {
>>> +               /* skip "trusted." attributes for unprivileged callers */
>>> +               if (!trusted && xattr_is_trusted(xattr->name))
>>> +                       continue;
>>> +
>>> +               used += strlen(xattr->name) + 1;
>>> +               if (buffer) {
>>> +                       if (size < used) {
>>> +                               used = -ERANGE;
>>> +                               break;
>>> +                       }
>>> +                       strncpy(buffer, xattr->name, strlen(xattr->name) + 1);
>>>+                        buffer += strlen(xattr->name) + 1;
>>
>> Why are you doing a strncpy here?  strcpy() 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
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