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Date:   Tue, 5 Jan 2021 08:57:31 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     "Eric W. Biederman" <ebiederm@xmission.com>
Cc:     Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
        Kees Cook <keescook@chromium.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: Does uaccess_kernel() work for detecting kernel thread?
Message-ID: <20210105075731.GB30414@lst.de>
References: <0bcc0c63-31a3-26fd-bccb-b28af0375c34@i-love.sakura.ne.jp> <87a6u5iw3d.fsf@x220.int.ebiederm.org>
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On Tue, Dec 22, 2020 at 11:33:58AM -0600, Eric W. Biederman wrote:
> I do wonder though if perhaps we should create a is_user_cred helper to
> detect the difference between the creds of kernel threads and the thread
> of ordinary userspace.   Which would handle io_uring that copy creds
> around and check them at a later time more cleanly.

I don't think we should as no one has a business to check this difference.
If there is a case where the creds are not correct for all access decisions
we need to fix that rather than adding hacks.