linux-ext4 - Re: [PATCH -V4 08/11] vfs: Add new file and directory create permission flags

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Message-Id: <181ED6EE-0B9F-4090-A911-B6053FF28BAC@dilger.ca>
Date:	Sun, 2 Jan 2011 22:59:00 -0700
From:	Andreas Dilger <adilger@...ger.ca>
To:	Andreas Dilger <adilger@...ger.ca>
Cc:	Ted Ts'o <tytso@....edu>, Andreas Gruenbacher <agruen@...e.de>,
	Jeff Layton <jlayton@...hat.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	"sfrench@...ibm.com" <sfrench@...ibm.com>,
	"ffilz@...ibm.com" <ffilz@...ibm.com>,
	"sandeen@...hat.com" <sandeen@...hat.com>,
	"bfields@...i.umich.edu" <bfields@...i.umich.edu>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"nfsv4@...ux-nfs.org" <nfsv4@...ux-nfs.org>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -V4 08/11] vfs: Add new file and directory create permission flags

Never mind, I didn't notice this was only for hard linking directories...

Cheers, Andreas

On 2011-01-02, at 22:20, Andreas Dilger <adilger@...ger.ca> wrote:

> Actually, I think it is required by POSIX that EXDEV is returned when cross-linking files. For mv calling rename() at least it uses a return EXDEV to copy the file to the target filesystem instead of just giving up and returning an error. It may be other applications like tar have a similar dependency for link(). 
> 
> Cheers, Andreas
> 
> On 2011-01-02, at 16:21, Ted Ts'o <tytso@....edu> wrote:
> 
>> I was going through some old patches in the ext4 patchwork list, and
>> came across this.  It looks like this patch has never been applied to
>> mainline.  If it's a "clear improvement", any reason not to submit it?
>> 
>> Regards,
>> 
>>                                        - Ted
>> 
>> On Mon, Sep 27, 2010 at 03:14:00PM +0200, Andreas Gruenbacher wrote:
>>> 
>>> Ah, you mean this:
>>> 
>>> --- a/fs/namei.c
>>> +++ b/fs/namei.c
>>> @@ -2450,7 +2450,9 @@ int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_de
>>>   if (!inode)
>>>       return -ENOENT;
>>> 
>>> -    error = may_create(dir, new_dentry, S_ISDIR(inode->i_mode));
>>> +    if (S_ISDIR(inode->i_mode))
>>> +        return -EPERM;
>>> +    error = may_create(dir, new_dentry, 0);
>>>   if (error)
>>>       return error;
>>> 
>>> @@ -2464,8 +2466,6 @@ int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_de
>>>       return -EPERM;
>>>   if (!dir->i_op->link)
>>>       return -EPERM;
>>> -    if (S_ISDIR(inode->i_mode))
>>> -        return -EPERM;
>>> 
>>>   error = security_inode_link(old_dentry, dir, new_dentry);
>>>   if (error)
>>> 
>>> This is a clear improvement; I don't think it matters that user-space will
>>> get -EPERM instead of -EXDEV when trying to hard-link a directory across
>>> devices.
>>> 
>>> Thanks,
>>> Andreas
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