From: "Mickaël Salaün" <mic@digikod.net>
To: "Thomas Weißschuh" <linux@weissschuh.net>
Cc: David Howells <dhowells@redhat.com>,
David Woodhouse <dwmw2@infradead.org>,
Jarkko Sakkinen <jarkko@kernel.org>,
keyrings@vger.kernel.org, linux-kernel@vger.kernel.org,
Mark Pearson <markpearson@lenovo.com>,
Eric Snowberg <eric.snowberg@oracle.com>,
linux-integrity@vger.kernel.org,
linux-security-module@vger.kernel.org
Subject: Re: [PATCH] certs: Prevent spurious errors on repeated blacklisting
Date: Mon, 7 Nov 2022 17:20:53 +0100 [thread overview]
Message-ID: <8692915f-437c-56fd-8984-d6febf533fa9@digikod.net> (raw)
In-Reply-To: <db5890d8-3a3d-4ca7-bb58-655c26164587@t-8ch.de>
On 07/11/2022 16:55, Thomas Weißschuh wrote:
> On 2022-11-07 14:12+0100, Mickaël Salaün wrote:
>> This is a follow-up of
>> https://lore.kernel.org/r/c8c65713-5cda-43ad-8018-20f2e32e4432@t-8ch.de
>>
>> Added Jarkko, Mark Pearson, Eric Snowberg and more ML in Cc.
>>
>>
>> On 04/11/2022 02:47, Thomas Weißschuh wrote:
>>> When the blacklist keyring was changed to allow updates from the root
>>> user it gained an ->update() function that disallows all updates.
>>> When the a hash is blacklisted multiple times from the builtin or
>>> firmware-provided blacklist this spams prominent logs during boot:
>>>
>>> [ 0.890814] blacklist: Problem blacklisting hash (-13)
>>>
>>> As all these repeated calls to mark_raw_hash_blacklisted() would create
>>> the same keyring entry again anyways these errors can be safely ignored.
>>
>> These errors can indeed be safely ignored, however they highlight issues
>> with some firmware vendors not checking nor optimizing their blocked hashes.
>> This raises security concerns, and it should be fixed by firmware vendors.
>
> Thanks, I was not aware that these are worth fixing.
>
>>> Fixes: 6364d106e041 ("certs: Allow root user to append signed hashes to the blacklist keyring")
>>> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
>>> ---
>>> certs/blacklist.c | 4 +++-
>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/certs/blacklist.c b/certs/blacklist.c
>>> index 41f10601cc72..5f7f2882ced7 100644
>>> --- a/certs/blacklist.c
>>> +++ b/certs/blacklist.c
>>> @@ -191,7 +191,9 @@ static int mark_raw_hash_blacklisted(const char *hash)
>>> BLACKLIST_KEY_PERM,
>>> KEY_ALLOC_NOT_IN_QUOTA |
>>> KEY_ALLOC_BUILT_IN);
>>> - if (IS_ERR(key)) {
>>> +
>>> + /* Blacklisting the same hash twice fails but would be idempotent */
>>> + if (IS_ERR(key) && PTR_ERR(key) != -EACCES) {
>>
>> We should not hide EACCES errors. This logs issues, which is correct for
>> duplicate hashes, and can help firmware vendors to fix their database. I'd
>> really like to see a different log message instead: change the duplicate
>> entry error code from EACCES to EEXIST, and call pr_warn for this specific
>> case.
>
> Returning EACCES would require some deeper changes to how the keyring is set up
I guess you meant EEXIST?
> or even changes to the keyring core itself to introduce a key_create() (without
> update) function.
>
> Is this something you would take a look at, or should I try to do it?
> (I have no previous knowledge about the keyring subsystem)
Please take a look. I think it should not be too complex.
>
> In any case it probably would also be good to log the problematic hashes
> themselves, so users can properly report the issue to their firmware vendors.
Agree
>
>>> pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key));
>>> return PTR_ERR(key);
>>> }
>>>
>>> base-commit: ee6050c8af96bba2f81e8b0793a1fc2f998fcd20
next prev parent reply other threads:[~2022-11-07 16:23 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-04 1:47 [PATCH] certs: Prevent spurious errors on repeated blacklisting Thomas Weißschuh
2022-11-07 13:12 ` Mickaël Salaün
2022-11-07 15:55 ` Thomas Weißschuh
2022-11-07 16:20 ` Mickaël Salaün [this message]
2022-11-07 16:35 ` Thomas Weißschuh
2022-11-07 19:40 ` Mickaël Salaün
2022-11-15 23:57 ` Jarkko Sakkinen
2022-11-09 15:50 ` Eric Snowberg
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