linux-ext4 - Re: [PATCH] ioctl_getfsmap.2: document the GETFSMAP ioctl

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Message-ID: <20170508184112.GJ5973@birch.djwong.org>
Date:   Mon, 8 May 2017 11:41:12 -0700
From:   "Darrick J. Wong" <darrick.wong@...cle.com>
To:     Jann Horn <jannh@...gle.com>
Cc:     Michael Kerrisk-manpages <mtk.manpages@...il.com>,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, Linux API <linux-api@...r.kernel.org>,
        linux-man@...r.kernel.org
Subject: Re: [PATCH] ioctl_getfsmap.2: document the GETFSMAP ioctl

On Mon, May 08, 2017 at 12:17:53AM +0200, Jann Horn wrote:
> On Sun, May 7, 2017 at 5:58 PM, Darrick J. Wong <darrick.wong@...cle.com> wrote:
> > Document the new GETFSMAP ioctl that returns the physical layout of a
> > (disk-based) filesystem.
> [...]
> > +.B EPERM
> > +This query is not allowed.
> 
> Please document the circumstances under which a query is allowed.

For the two current implementations, queries are always allowed.

(The doc could be more explicit about this decision being left to the
implementation.)

> Also: From a quick glance at the XFS implementation, I don't see any
> privilege checks. Am I missing something, or does this API permit an
> unprivileged user to determine the number of physical blocks allocated
> for any inode, even for inodes the user can't ordinarily see in any
> way?

Correct.

--D

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