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

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Message-Id: <7BB7EE30-257A-4B27-B420-B0C72292444A@suse.de>
Date:   Wed, 13 Oct 2021 12:53:48 +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] [PATCH] Revert "efi/random: Treat EFI_RNG_PROTOCOL
 output as bootloader randomness"



> On 13 Oct 2021, at 12:51, Ivan T. Ivanov <iivanov@...e.de> wrote:
> 
> Hi,
> 
>> On 13 Oct 2021, at 10:50, Ard Biesheuvel <ardb@...nel.org> 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 doesn’t boot. I just changed following and kernel panics.  
> 
> - credit_entropy
> + credit_entropy_bits
> 
> Please see attached file.
> 

Ah, sorry. I missed file attachment. Now it should be fine.


Download attachment "panic.log" of type "application/octet-stream" (3150 bytes)



Ivan