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

From: Guenter Roeck <linux@roeck-us.net>
To: Mark Brown <broonie@kernel.org>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>,
	linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
	linux-arch@vger.kernel.org, Dinh Nguyen <dinguyen@kernel.org>,
	Nick Hu <nickhu@andestech.com>, Max Filippov <jcmvbkbc@gmail.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	"David S . Miller" <davem@davemloft.net>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Michal Simek <monstr@monstr.eu>, Borislav Petkov <bp@alien8.de>,
	Guo Ren <guoren@kernel.org>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Joshua Kinard <kumba@gentoo.org>,
	David Laight <David.Laight@aculab.com>,
	Dominik Brodowski <linux@dominikbrodowski.net>,
	Eric Biggers <ebiggers@google.com>,
	Ard Biesheuvel <ardb@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Andy Lutomirski <luto@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	Lennart Poettering <mzxreary@0pointer.de>,
	Konstantin Ryabitsev <konstantin@linuxfoundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Theodore Ts'o <tytso@mit.edu>
Subject: Re: [PATCH v1] random: block in /dev/urandom
Date: Tue, 22 Mar 2022 14:54:20 -0700	[thread overview]
Message-ID: <0d20fb04-81b8-eeee-49ab-5b0a9e78c9f8@roeck-us.net> (raw)
In-Reply-To: <YjoUU+8zrzB02pW7@sirena.org.uk>

On 3/22/22 11:24, Mark Brown wrote:
> On Tue, Mar 22, 2022 at 08:58:20AM -0700, Guenter Roeck wrote:
> 
>> 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.
> 
> Just as a datapoint for debugging at least qemu/arm is getting coverage
> in CI systems (KernelCI is covering a bunch of different emulated
> machines and LKFT has at least one configuration as well, clang's tests
> have some wider architecture coverage as well I think) and they don't
> seem to be seeing any problems - there's some other variable in there.
> 
> For example current basic boot tests for KernelCI are at:
> 
>     https://linux.kernelci.org/test/job/mainline/branch/master/kernel/v5.17-1442-gb47d5a4f6b8d/plan/baseline/
> 
> for mainline and -next has:
> 
>     https://linux.kernelci.org/test/job/next/branch/master/kernel/next-20220322/plan/baseline/
> 
> These are with a buildroot based rootfs that has a "Saving random seed: "
> step in the boot process FWIW.

I use buildroot 2021.02.3. I have not changed the buildroot code, and it
still seems to be the same in 2022.02. I don't see the problem with all
boot tests, only with the architectures mentioned above, and not with all
qemu machines on the affected platforms. For arm, mostly older machines
are affected (versatile, realview, pxa configurations, collie, integratorcp,
sx1, mps2-an385, vexpress-a9, cubieboard). I didn't check, but maybe
kernelci doesn't test those machines ?

Guenter