Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 18 Feb 2020 12:14:53 -0500
From:   "Theodore Y. Ts'o" <tytso@mit.edu>
To:     Mark Salyzyn <salyzyn@android.com>
Cc:     Rob Herring <robh@kernel.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Android Kernel Team <kernel-team@android.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Richard Henderson <richard.henderson@linaro.org>,
        Mark Brown <broonie@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Hsin-Yi Wang <hsinyi@chromium.org>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Arvind Sankar <nivedita@alum.mit.edu>,
        Dominik Brodowski <linux@dominikbrodowski.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        Alexander Potapenko <glider@google.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
        Juergen Gross <jgross@suse.com>,
        Linux Doc Mailing List <linux-doc@vger.kernel.org>
Subject: Re: [PATCH 2/3] random: rng-seed source is utf-8
Message-ID: <20200218171453.GE147128@mit.edu>
References: <158166060044.9887.549561499483343724.stgit@devnote2>
 <158166062748.9887.15284887096084339722.stgit@devnote2>
 <CAL_Jsq+BDfWgGTVtppD-JEFHZRqpc00WaV2N7c6qsPBSaxOEPw@mail.gmail.com>
 <20200214224744.GC439135@mit.edu>
 <f15511bf-b840-0633-3354-506b7b0607fe@android.com>
 <20200215005336.GD439135@mit.edu>
 <243ab5a8-2ce1-1465-0175-3f5d483cbde1@android.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <243ab5a8-2ce1-1465-0175-3f5d483cbde1@android.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Feb 18, 2020 at 08:01:51AM -0800, Mark Salyzyn wrote:
> I am additionally concerned about add_bootloader_randomness() because it is
> possible for it to sleep because of add_hwgenerator_randomness() as once it
> hits the entropy threshold. As-is it can not be used inside start_kernel()
> because the sleep would result in a kernel panic, and I suspect its use
> inside early_init_dt_scan_chosen() for the commit "fdt: add support for
> rng-seed" might also be problematic since it is effectively called
> underneath start_kernel() is it not?
> 
> If add_bootloader_randomness was rewritten to call add_device_randomness()
> always, and when trusted also called the functionality of the new
> credit_trusted_entropy_bits (no longer needing to be exported if so), then
> the function could be used in both start_kernel() and
> early_init_dt_scan_chosen().

That's a good point, and it's a bug in add_bootloader_randomness().
That should be easily fixed by simply having it call mix_pool_bytes()
and credit_entropy_bits() directly.  I'll create a patch...

    			  	     	  	   - Ted