Re: [RESEND] Re: [PATCH] Revert "efi/random: Treat EFI_RNG_PROTOCOL output as bootloader randomness"

[Ivan T. Ivanov]

On 2021-10-13 10:50, Ard Biesheuvel wrote:
> On Wed, 13 Oct 2021 at 09:30, Ivan T. Ivanov <iivanov@xxxxxxx> wrote:
> > Hi,
> >
> > Quoting Dominik Brodowski (2021-10-12 11:40:34)
> > > Am Tue, Oct 12, 2021 at 11:27:08AM +0300 schrieb Ivan T. Ivanov:
> > > > This reverts commit 18b915ac6b0ac5ba7ded03156860f60a9f16df2b.
> > > >
> > > > When CONFIG_RANDOM_TRUST_BOOTLOADER is enabled add_bootloader_randomness()
> > > > calls add_hwgenerator_randomness() which might sleep,
> > >
> > > Wouldn't it be better to fix add_bootloader_randomness(), considering
> > > that
> > > calls to that function are likely to happen quite early during kernel
> > > initialization? Especially as it seems to have worked beforehand?
> >
> > I have tried. I made wait_event_interruptible() optional, but then
> > crng_reseed() segfault badly. And I don't think crng_reseed() is
> > something that I could fix easily. Suggestions are welcomed ;-)
>
> How about
>
> diff --git a/drivers/char/random.c b/drivers/char/random.c
> index 605969ed0f96..1828dc691ebf 100644
> --- a/drivers/char/random.c
> +++ b/drivers/char/random.c
> @@ -2297,9 +2297,8 @@ EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
>   */
>  void add_bootloader_randomness(const void *buf, unsigned int size)
>  {
> +       add_device_randomness(buf, size);
>         if (IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER))
> -               add_hwgenerator_randomness(buf, size, size * 8);
> -       else
> -               add_device_randomness(buf, size);
> +               credit_entropy(&input_pool, size * 8);
>  }
>  EXPORT_SYMBOL_GPL(add_bootloader_randomness);

This is more or less what I have done. credit_entropy() calls
crng_reseed() which crash badly.

Will check again, but I am sure it will give me same result.

Regards,
Ivan