linux-kernel - Re: [PATCH 1/2] powerpc/pseries: block untrusted device tree changes when locked down

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Message-ID: <875yheqdzq.fsf@linux.ibm.com>
Date:   Fri, 23 Sep 2022 10:58:33 -0500
From:   Nathan Lynch <nathanl@...ux.ibm.com>
To:     Paul Moore <paul@...l-moore.com>
Cc:     linuxppc-dev@...ts.ozlabs.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, jmorris@...ei.org,
        mpe@...erman.id.au, serge@...lyn.com, ajd@...ux.ibm.com,
        gcwilson@...ux.ibm.com, nayna@...ux.ibm.com
Subject: Re: [PATCH 1/2] powerpc/pseries: block untrusted device tree
 changes when locked down

Paul Moore <paul@...l-moore.com> writes:
>> diff --git a/include/linux/security.h b/include/linux/security.h
>> index 7bd0c490703d..1ca8dbacd3cc 100644
>> --- a/include/linux/security.h
>> +++ b/include/linux/security.h
>> @@ -122,6 +122,7 @@ enum lockdown_reason {
>>         LOCKDOWN_XMON_WR,
>>         LOCKDOWN_BPF_WRITE_USER,
>>         LOCKDOWN_DBG_WRITE_KERNEL,
>> +       LOCKDOWN_DEVICE_TREE,
>
> I would suggest moving LOCKDOWN_DEVICE_TREE to be next to
> LOCKDOWN_ACPI_TABLES.  It's not a hard requirement, but it seems like
> a nice idea to group similar things when we can.
>
>>         LOCKDOWN_INTEGRITY_MAX,
>>         LOCKDOWN_KCORE,
>>         LOCKDOWN_KPROBES,
>> diff --git a/security/security.c b/security/security.c
>> index 4b95de24bc8d..2863fc31eec6 100644
>> --- a/security/security.c
>> +++ b/security/security.c
>> @@ -60,6 +60,7 @@ const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
>>         [LOCKDOWN_XMON_WR] = "xmon write access",
>>         [LOCKDOWN_BPF_WRITE_USER] = "use of bpf to write user RAM",
>>         [LOCKDOWN_DBG_WRITE_KERNEL] = "use of kgdb/kdb to write kernel RAM",
>> +       [LOCKDOWN_DEVICE_TREE] = "modifying device tree contents",
>
> Might as well move this one too.

Yes, I can do that for v2. Thanks.