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

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Date:   Wed, 13 Oct 2021 16:23:31 +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"

Hi,

> On 13 Oct 2021, at 12:53, Ivan T. Ivanov <iivanov@...e.de> wrote:
> 
> 
> 
>> 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.  
>> 

And before anyone asked “.. Hey but this is 5.3.18 kernel version”
here is the kernel panic with 5.14.11 :-)

Regards,
Ivan


Download attachment "kernel-5.14-panic.log" of type "application/octet-stream" (3284 bytes)