Date: Fri, 4 Dec 2015 17:43:49 -0600
From: "Serge E. Hallyn" <serge.hallyn@ubuntu.com>
To: "Theodore Ts'o" <tytso@mit.edu>, Seth Forshee <seth.forshee@canonical.com>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Serge Hallyn <serge.hallyn@canonical.com>,
        Richard Weinberger <richard.weinberger@gmail.com>,
        Austin S Hemmelgarn <ahferroin7@gmail.com>,
        Miklos Szeredi <miklos@szeredi.hu>, linux-bcache@vger.kernel.org,
        dm-devel@redhat.com, linux-raid@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org,
        linux-fsdevel@vger.kernel.org, fuse-devel@lists.sourceforge.net,
        linux-security-module@vger.kernel.org, selinux@tycho.nsa.gov
Subject: Re: [PATCH 14/19] fs: Permit FIBMAP for users with CAP_SYS_RAWIO in
 s_user_ns
Message-ID: <20151204234348.GA6908@mail.hallyn.com>
References: <1449070821-73820-1-git-send-email-seth.forshee@canonical.com>
 <1449070821-73820-15-git-send-email-seth.forshee@canonical.com>
 <20151204191143.GE3624@mail.hallyn.com>
 <20151204200528.GC18359@thunk.org>
 <20151204200736.GJ3624@mail.hallyn.com>
 <20151204204532.GG147214@ubuntu-hedt>
 <20151204231152.GE18359@thunk.org>
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On Fri, Dec 04, 2015 at 06:11:52PM -0500, Theodore Ts'o wrote:
> On Fri, Dec 04, 2015 at 02:45:32PM -0600, Seth Forshee wrote:
> > On Fri, Dec 04, 2015 at 02:07:36PM -0600, Serge E. Hallyn wrote:
> > > Heh, I was looking over http://www.gossamer-threads.com/lists/linux/kernel/103611
> > > a little while ago :)  The same question was asked 16 years ago.  Apparently
> > > the answer then was that it was easier than fixing the code.
> > 
> > So it seems then that either it still isn't safe and so unprivileged
> > users shouldn't be allowed to do it at all, or else it's safe and we
> > should drop the requirement completely. I can't say which is right,
> > unfortunately.
> 
> It may not have been safe 16 years agoo, but giving invalid arguments
> to FIBMAP is safe for ext4 and ext2.  This is the sort of thing that
> tools like trinity should and does test for, so I think it should be
> fine to remove the root check for FIBMAP.

Seth, can I tempt you into sending a standalone patch to remove that? :)

-serge
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