linux-kernel - Re: [PATCH 5.10 000/163] 5.10.119-rc1 review

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Message-ID: <YpE+S2H301IsZYzv@zx2c4.com>
Date:   Fri, 27 May 2022 23:10:35 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Pavel Machek <pavel@...x.de>, Chris.Paterson2@...esas.com,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
        shuah@...nel.org, patches@...nelci.org,
        lkft-triage@...ts.linaro.org, jonathanh@...dia.com,
        f.fainelli@...il.com, sudipm.mukherjee@...il.com,
        slade@...dewatkins.com
Subject: Re: [PATCH 5.10 000/163] 5.10.119-rc1 review

Hi Guenter,

On Fri, May 27, 2022 at 09:59:14AM -0700, Guenter Roeck wrote:
> Given that we (ChromeOS) have been hit by rng related
> issues before (specifically boot stalls on some hardware), I am quite
> concerned about the possible impact of this series for stable releases.

The urandom try_to_generate_entropy() change from 5.18 wasn't backported.

zx2c4@...nkpad ~/Projects/random-linux $ git diff linux-5.10.y:drivers/char/random.c master:drivers/char/random.c
[...snip...]
@@ -1292,6 +1311,13 @@ static ssize_t urandom_read_iter(struct kiocb *kiocb, struct iov_iter *iter)
 {
        static int maxwarn = 10;

+       /*
+        * Opportunistically attempt to initialize the RNG on platforms that
+        * have fast cycle counters, but don't (for now) require it to succeed.
+        */
+       if (!crng_ready())
+               try_to_generate_entropy();
+
        if (!crng_ready()) {
                if (!ratelimit_disable && maxwarn <= 0)
                        ++urandom_warning.missed;



Jason