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

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Message-ID: <e8c2ce11ec8b6193d891288ce6b3caa0@suse.de>
Date:   Wed, 13 Oct 2021 11:05:39 +0300
From:   "Ivan T. Ivanov" <iivanov@...e.de>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Dominik Brodowski <linux@...inikbrodowski.net>,
        linux-efi <linux-efi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND] Re: [PATCH] Revert "efi/random: Treat EFI_RNG_PROTOCOL
 output as bootloader randomness"

On 2021-10-13 10:50, Ard Biesheuvel wrote:
> On Wed, 13 Oct 2021 at 09:30, Ivan T. Ivanov <iivanov@...e.de> 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