linux-kernel - Re: [PATCH v1 1/1] certs: Explain the rational to call panic()

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Date:   Tue, 22 Mar 2022 11:53:07 +0100
From:   Mickaël Salaün <mic@...ikod.net>
To:     Paul Moore <paul@...l-moore.com>
Cc:     Jarkko Sakkinen <jarkko@...nel.org>,
        David Howells <dhowells@...hat.com>,
        "David S . Miller" <davem@...emloft.net>,
        David Woodhouse <dwmw2@...radead.org>,
        Eric Snowberg <eric.snowberg@...cle.com>,
        keyrings@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Mickaël Salaün <mic@...ux.microsoft.com>
Subject: Re: [PATCH v1 1/1] certs: Explain the rational to call panic()


On 21/03/2022 19:23, Paul Moore wrote:
> On Mon, Mar 21, 2022 at 1:45 PM Mickaël Salaün <mic@...ikod.net> wrote:
>>
>> From: Mickaël Salaün <mic@...ux.microsoft.com>
>>
>> The blacklist_init() function calls panic() for memory allocation
>> errors.  This change documents the reason why we don't return -ENODEV.
>>
>> Suggested-by: Paul Moore <paul@...l-moore.com> [1]
>> Requested-by: Jarkko Sakkinen <jarkko@...nel.org> [1]
>> Link: https://lore.kernel.org/r/YjeW2r6Wv55Du0bJ@iki.fi [1]
>> Signed-off-by: Mickaël Salaün <mic@...ux.microsoft.com>
>> Link: https://lore.kernel.org/r/20220321174548.510516-2-mic@digikod.net
>> ---
>>   certs/blacklist.c | 8 ++++++++
>>   1 file changed, 8 insertions(+)
> 
> I would suggest changing the second sentence as shown below, but
> otherwise it looks good to me.
> 
> Reviewed-by: Paul Moore <paul@...l-moore.com>
> 
>> diff --git a/certs/blacklist.c b/certs/blacklist.c
>> index 486ce0dd8e9c..ac26bcf9b9a5 100644
>> --- a/certs/blacklist.c
>> +++ b/certs/blacklist.c
>> @@ -307,6 +307,14 @@ static int restrict_link_for_blacklist(struct key *dest_keyring,
>>
>>   /*
>>    * Initialise the blacklist
>> + *
>> + * The blacklist_init() function is registered as an initcall via
>> + * device_initcall().  As a result the functionality doesn't load and the
> 
> "As a result if the blacklist_init() function fails for any reason the
> kernel continues to execute."

Thanks, I'll fix that.

> 
>> + * kernel continues on executing.  While cleanly returning -ENODEV could be
>> + * acceptable for some non-critical kernel parts, if the blacklist keyring
>> + * fails to load it defeats the certificate/key based deny list for signed
>> + * modules.  If a critical piece of security functionality that users expect to
>> + * be present fails to initialize, panic()ing is likely the right thing to do.
>>    */
>>   static int __init blacklist_init(void)
>>   {
> 
> --
> paul-moore.com