linux-kernel - Re: [PATCH v1] random: block in /dev/urandom

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Message-ID: <d5c23f68-30ba-a5eb-6bea-501736e79c88@roeck-us.net>
Date:   Tue, 22 Mar 2022 10:56:44 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-arch@...r.kernel.org, Dinh Nguyen <dinguyen@...nel.org>,
        Nick Hu <nickhu@...estech.com>,
        Max Filippov <jcmvbkbc@...il.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        "David S . Miller" <davem@...emloft.net>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Michal Simek <monstr@...str.eu>,
        Borislav Petkov <bp@...en8.de>, Guo Ren <guoren@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Joshua Kinard <kumba@...too.org>,
        David Laight <David.Laight@...lab.com>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Eric Biggers <ebiggers@...gle.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Lennart Poettering <mzxreary@...inter.de>,
        Konstantin Ryabitsev <konstantin@...uxfoundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH v1] random: block in /dev/urandom

On 3/22/22 10:09, Jason A. Donenfeld wrote:
> Hey Guenter,
> 
> On Tue, Mar 22, 2022 at 08:58:20AM -0700, Guenter Roeck wrote:
>> On Thu, Feb 17, 2022 at 05:28:48PM +0100, Jason A. Donenfeld wrote:
>>> This topic has come up countless times, and usually doesn't go anywhere.
>>> This time I thought I'd bring it up with a slightly narrower focus,
>>> updated for some developments over the last three years: we finally can
>>> make /dev/urandom always secure, in light of the fact that our RNG is
>>> now always seeded.
>>>
>>
>> [ ... ]
>>
>> This patch (or a later version of it) made it into mainline and causes a
>> large number of qemu boot test failures for various architectures (arm,
>> m68k, microblaze, sparc32, xtensa are the ones I observed). Common
>> denominator is that boot hangs at "Saving random seed:". A sample bisect
>> log is attached. Reverting this patch fixes the problem.
> 
> As Linus said, it was worth a try, but I guess it just didn't work. For
> my own curiosity, though, do you have a link to those QEMU VMs you could
> share? I'd sort of like to poke around, and if we do ever reattempt this
> sometime down the road, it seems like understanding everything about why
> the previous time failed might be a good idea.
> 

Everything - including the various root file systems - is at
git@...hub.com:groeck/linux-build-test.git. Look into rootfs/ for the
various boot tests. I'll be happy to provide some qemu command lines
if needed.

Guenter