linux-kernel - Re: [RFC v6 03/40] vfs: Add MAY_DELETE_SELF and MAY_DELETE

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Message-ID: <CALCETrUoBnPyEGExpoDzHOCgnHh5=a1ROALmb63LLJZG+L=aQA@mail.gmail.com>
Date:	Fri, 28 Aug 2015 14:36:15 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Andreas Gruenbacher <andreas.gruenbacher@...il.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	linux-nfs@...r.kernel.org, Linux API <linux-api@...r.kernel.org>,
	linux-cifs@...r.kernel.org,
	LSM List <linux-security-module@...r.kernel.org>,
	Andreas Gruenbacher <agruenba@...hat.com>
Subject: Re: [RFC v6 03/40] vfs: Add MAY_DELETE_SELF and MAY_DELETE_CHILD
 permission flags

On Tue, Aug 4, 2015 at 4:53 AM, Andreas Gruenbacher
<andreas.gruenbacher@...il.com> wrote:
> Normally, deleting a file requires write and execute access to the parent
> directory.  With Richacls, a process with MAY_DELETE_SELF access to a file
> may delete the file even without write access to the parent directory.
>
> To support that, pass the MAY_DELETE_CHILD mask flag to inode_permission()
> when checking for delete access inside a directory, and MAY_DELETE_SELF
> when checking for delete access to a file itelf.
>
> The MAY_DELETE_SELF permission does not override the sticky directory
> check.  It probably should.

Silly question from the peanut gallery: is there any such thing as
opening an fd pointing at a file such that the "open file description"
(i.e. the struct file) captures the right to delete the file?

IOW do we need FMODE_DELETE_SELF?

--Andy
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