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

[Guenter Roeck]

On Fri, May 27, 2022 at 11:10:35PM +0200, Jason A. Donenfeld wrote:
> 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.
> 

Was it not backported on purpose or is it missing ?

Thanks,
Guenter

> zx2c4@thinkpad ~/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