linux-kernel - Re: [PATCH 5/5] man-pages: cap_rights

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Message-ID: <20140701091900.GB2242@google.com>
Date:	Tue, 1 Jul 2014 10:19:00 +0100
From:	David Drysdale <drysdale@...gle.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	LSM List <linux-security-module@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Meredydd Luff <meredydd@...atehouse.org>,
	Kees Cook <keescook@...omium.org>,
	James Morris <james.l.morris@...cle.com>,
	Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH 5/5] man-pages: cap_rights_get: retrieve Capsicum fd
 rights

On Mon, Jun 30, 2014 at 03:28:14PM -0700, Andy Lutomirski wrote:
> On Mon, Jun 30, 2014 at 3:28 AM, David Drysdale <drysdale@...gle.com> wrote:
> > Signed-off-by: David Drysdale <drysdale@...gle.com>
> > ---
> >  man2/cap_rights_get.2 | 126 ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 126 insertions(+)
> >  create mode 100644 man2/cap_rights_get.2
> >
> > diff --git a/man2/cap_rights_get.2 b/man2/cap_rights_get.2
> > new file mode 100644
> > index 000000000000..966c0ed7e336
> > --- /dev/null
> > +++ b/man2/cap_rights_get.2
> > @@ -0,0 +1,126 @@
> > +.\"
> > +.\" Copyright (c) 2008-2010 Robert N. M. Watson
> > +.\" Copyright (c) 2012-2013 The FreeBSD Foundation
> > +.\" Copyright (c) 2013-2014 Google, Inc.
> > +.\" All rights reserved.
> > +.\"
> > +.\" %%%LICENSE_START(BSD_2_CLAUSE)
> > +.\" Redistribution and use in source and binary forms, with or without
> > +.\" modification, are permitted provided that the following conditions
> > +.\" are met:
> > +.\" 1. Redistributions of source code must retain the above copyright
> > +.\"    notice, this list of conditions and the following disclaimer.
> > +.\" 2. Redistributions in binary form must reproduce the above copyright
> > +.\"    notice, this list of conditions and the following disclaimer in the
> > +.\"    documentation and/or other materials provided with the distribution.
> > +.\"
> > +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
> > +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
> > +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
> > +.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
> > +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
> > +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
> > +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
> > +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
> > +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
> > +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
> > +.\" SUCH DAMAGE.
> > +.\" %%%LICENSE_END
> > +.\"
> > +.TH CAP_RIGHTS_GET 2 2014-05-07 "Linux" "Linux Programmer's Manual"
> > +.SH NAME
> > +cap_rights_get \- retrieve Capsicum capability rights
> > +.SH SYNOPSIS
> > +.nf
> > +.B #include <sys/capsicum.h>
> > +.sp
> > +.BI "int cap_rights_get(int " fd ", struct cap_rights *" rights ,
> > +.BI "                   unsigned int *" fcntls ,
> > +.BI "                   int *" nioctls ", unsigned int *" ioctls );
> > +.SH DESCRIPTION
> > +Obtain the current Capsicum capability rights for a file descriptor.
> > +.PP
> > +The function will fill the
> > +.I rights
> > +argument (if non-NULL) with the primary capability rights of the
> > +.I fd
> > +descriptor.  The result can be examined with the
> > +.BR cap_rights_is_set (3)
> > +family of functions.  The complete list of primary rights can be found in the
> > +.BR rights (7)
> > +manual page.
> > +.PP
> > +If the
> > +.I fcntls
> > +argument is non-NULL, it will be filled in with a bitmask of allowed
> > +.BR fcntl (2)
> > +commands; see
> > +.BR cap_rights_limit (2)
> > +for values.  If the file descriptor does not have the
> > +.B CAP_FCNTL
> > +primary right, the returned
> > +.I fcntls
> > +value will be zero.
> > +.PP
> > +If the
> > +.I nioctls
> > +argument is non-NULL, it will be filled in with the number of allowed
> > +.BR ioctl (2)
> > +commands, or with the value CAP_IOCTLS_ALL to indicate that all
> > +.BR ioctl (2)
> > +commands are allowed.  If the file descriptor does not have the
> > +.B CAP_IOCTL
> > +primary right, the returned
> > +.I nioctls
> > +value will be zero.
> > +.PP
> > +The
> > +.I ioctls
> > +argument (if non-NULL) should point at memory that can hold up to
> > +.I nioctls
> > +values.
> > +The system call populates the provided buffer with up to
> > +.I nioctls
> > +elements, but always returns the total number of
> 
> I assume you mean "up to the initial value of *nioctls elements" or
> something.  Can you clarify?
> 
> --Andy

Yeah, that's what I meant.  Is this clearer?

  If  the  ioctls argument is non-NULL, the caller should specify
  the size of the provided buffer as the  initial  value  of  the
  nioctls  argument (as a count of the number of ioctl(2) command
  values the buffer can hold).  On successful completion  of  the
  system call, the ioctls buffer is filled with the ioctl(2) com‐
  mand values, up to maximum of the initial value of nioctls.

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