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Date: Fri, 16 Mar 2018 01:49:41 -0700
From: Christoph Hellwig <hch@infradead.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Al Viro <viro@zeniv.linux.org.uk>, Andy Lutomirski <luto@kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v2 17/36] fs: add ksys_chroot() helper; remove-in kernel
 calls to sys_chroot()
Message-ID: <20180316084941.GF4151@infradead.org>
References: <20180315190529.20943-1-linux@dominikbrodowski.net>
 <20180315190529.20943-18-linux@dominikbrodowski.net>
 <CAK8P3a2s2YsttKSjZfc8xW+kjv8M1hFDCg1E9nHPjq_KRvik2Q@mail.gmail.com>
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> > +       ksys_chroot(".");
> >         complete(&setup_done);
> >         while (1) {
> >                 spin_lock(&req_lock);
> 
> Could this be done using kern_path()/set_fs_root() instead so we
> avoid the __user pointer?

Agreed.  Especially as we don't need any of the permission checks here.