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[195.23.151.163]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49ce309e418sm85608165e9.13.2026.09.02.04.38.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 02 Sep 2026 04:38:43 -0700 (PDT) Sender: Julian Braha Message-ID: <7b7e4b45-dc5c-4328-bb51-5d1fac4c5586@gmail.com> Date: Wed, 2 Sep 2026 12:38:42 +0100 Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] ima: allow users to specify the pcr index with IMA_MEASURE_PCR_IDX To: Mimi Zohar , roberto.sassu@huawei.com, dmitry.kasatkin@gmail.com, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com Cc: eric.snowberg@oracle.com, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260824162215.1572367-1-julianbraha@gmail.com> <35ae5c9fd60874127d15f5fedb84c0a90e56eca4.camel@linux.ibm.com> Content-Language: en-US From: Julian Braha In-Reply-To: <35ae5c9fd60874127d15f5fedb84c0a90e56eca4.camel@linux.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Mimi, On 9/2/26 01:54, Mimi Zohar wrote: > On Mon, 2026-08-24 at 17:22 +0100, Julian Braha wrote: >> The IMA_MEASURE_PCR_IDX option is currently not visible in the kconfig >> frontend, so it always uses its default, 10. This means that the >> 'range 8 14' is dead code, and users are unable to specify the pcr index >> value. >> >> In a previous discussion, Mimi explained that users should be able to use >> this config option to specify the pcr index. [1] >> >> Let's add a prompt for users to specify the pcr index, when EXPERT is >> enabled. >> >> This dead range was found by kconfirm, a static analysis tool for Kconfig. >> >> Signed-off-by: Julian Braha >> --- >> Link: https://lore.kernel.org/all/1feff118-4afa-4b9c-86f1-271a7a88208f@gmail.com/T/#mc4efa2491b4937eb7c9e532c29ffba516a70e662 [1] >> --- >> security/integrity/ima/Kconfig | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig >> index b3a9f86809b0..2d5bb19ea6ac 100644 >> --- a/security/integrity/ima/Kconfig >> +++ b/security/integrity/ima/Kconfig >> @@ -46,6 +46,7 @@ config IMA_KEXEC >> >> config IMA_MEASURE_PCR_IDX >> int >> + prompt "PCR Index for Aggregate" if EXPERT >> range 8 14 >> default 10 >> help > > Thanks, Julian. The existing Help says, "If unsure, use the default 10." Could > we make this recommendation stronger? AI suggested: > > IMA_MEASURE_PCR_IDX determines the TPM PCR register index > that IMA uses to maintain the integrity aggregate of the > measurement list. Most attestation tooling expects PCR 10. > > The default is almost always what you want. Only change > this if you know what you are doing. Thank you for your feedback, will include this in v2! - Julian Braha