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Date:   Mon, 25 Jan 2021 18:06:40 +0100
From:   Christian Brauner <christian.brauner@ubuntu.com>
To:     "Serge E. Hallyn" <serge@hallyn.com>
Cc:     "Eric W. Biederman" <ebiederm@xmission.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Christoph Hellwig <hch@lst.de>, linux-fsdevel@vger.kernel.org,
        John Johansen <john.johansen@canonical.com>,
        James Morris <jmorris@namei.org>,
        Mimi Zohar <zohar@linux.ibm.com>,
        Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
        Stephen Smalley <stephen.smalley.work@gmail.com>,
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        Arnd Bergmann <arnd@arndb.de>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>,
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        Mrunal Patel <mpatel@redhat.com>,
        Josh Triplett <josh@joshtriplett.org>,
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Subject: Re: [PATCH v6 23/40] exec: handle idmapped mounts
Message-ID: <20210125170640.6ycsyod2ftxnzjzy@wittgenstein>
References: <20210121131959.646623-1-christian.brauner@ubuntu.com>
 <20210121131959.646623-24-christian.brauner@ubuntu.com>
 <875z3l0y56.fsf@x220.int.ebiederm.org>
 <20210125164404.aullgl3vlajgkef3@wittgenstein>
 <20210125170316.GA8345@mail.hallyn.com>
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On Mon, Jan 25, 2021 at 11:03:16AM -0600, Serge Hallyn wrote:
> On Mon, Jan 25, 2021 at 05:44:04PM +0100, Christian Brauner wrote:
> > On Mon, Jan 25, 2021 at 10:39:01AM -0600, Eric W. Biederman wrote:
> > > Christian Brauner <christian.brauner@ubuntu.com> writes:
> > > 
> > > > When executing a setuid binary the kernel will verify in bprm_fill_uid()
> > > > that the inode has a mapping in the caller's user namespace before
> > > > setting the callers uid and gid. Let bprm_fill_uid() handle idmapped
> > > > mounts. If the inode is accessed through an idmapped mount it is mapped
> > > > according to the mount's user namespace. Afterwards the checks are
> > > > identical to non-idmapped mounts. If the initial user namespace is
> > > > passed nothing changes so non-idmapped mounts will see identical
> > > > behavior as before.
> > > 
> > > This does not handle the v3 capabilites xattr with embeds a uid.
> > > So at least at that level you are missing some critical conversions.
> > 
> > Thanks for looking. Vfs v3 caps are handled earlier in the series. I'm
> > not sure what you're referring to here. There are tests in xfstests that
> > verify vfs3 capability behavior.
> 
> *just* to make sure i'm not misunderstanding - s/vfs3/v3/ right?

Yes, in my mind it's always as "vfs v3 caps -> vfs3 caps". Sorry for the
confusion.