linux-kernel - Re: [PATCH v8 07/12] KEYS: trusted: Remove dead branch from tpm2_unseal

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Message-ID: <aUUc6ftTmD-aUO6O@earth.li>
Date: Fri, 19 Dec 2025 09:37:45 +0000
From: Jonathan McDowell <noodles@...th.li>
To: Jarkko Sakkinen <jarkko@...nel.org>
Cc: linux-integrity@...r.kernel.org, David Howells <dhowells@...hat.com>,
	Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	Mimi Zohar <zohar@...ux.ibm.com>,
	"open list:KEYS/KEYRINGS" <keyrings@...r.kernel.org>,
	"open list:SECURITY SUBSYSTEM" <linux-security-module@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 07/12] KEYS: trusted: Remove dead branch from
 tpm2_unseal_cmd

On Tue, Dec 16, 2025 at 11:21:41AM +0200, Jarkko Sakkinen wrote:
>TPM2_Unseal requires TPM2_ST_SESSIONS, and tpm2_unseal_cmd() always does
>set up either password or HMAC session.
>
>Remove the branch in tpm2_unseal_cmd() conditionally setting
>TPM2_ST_NO_SESSIONS. It is faulty but luckily it is never exercised at
>run-time, and thus does not cause regressions.

Reviewed-by: Jonathan McDowell <noodles@...a.com>

>Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
>---
> security/keys/trusted-keys/trusted_tpm2.c | 10 +---------
> 1 file changed, 1 insertion(+), 9 deletions(-)
>
>diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
>index d3a5c5f2b926..3666e3e48eab 100644
>--- a/security/keys/trusted-keys/trusted_tpm2.c
>+++ b/security/keys/trusted-keys/trusted_tpm2.c
>@@ -451,10 +451,8 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
> 			   struct trusted_key_options *options,
> 			   u32 blob_handle)
> {
>-	struct tpm_header *head;
> 	struct tpm_buf buf;
> 	u16 data_len;
>-	int offset;
> 	u8 *data;
> 	int rc;
>
>@@ -495,14 +493,8 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
> 		tpm_buf_append_u16(&buf, options->blobauth_len);
> 		tpm_buf_append(&buf, options->blobauth, options->blobauth_len);
>
>-		if (tpm2_chip_auth(chip)) {
>+		if (tpm2_chip_auth(chip))
> 			tpm_buf_append_hmac_session(chip, &buf, TPM2_SA_ENCRYPT, NULL, 0);
>-		} else  {
>-			offset = buf.handles * 4 + TPM_HEADER_SIZE;
>-			head = (struct tpm_header *)buf.data;
>-			if (tpm_buf_length(&buf) == offset)
>-				head->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
>-		}
> 	}
>
> 	rc = tpm_buf_fill_hmac_session(chip, &buf);
>-- 
>2.39.5
>
>

J.

-- 
"Never test for an error condition you don't know how to handle."
  --Steinbach