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

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Message-ID: <aVfy6lcJ0F6vzY_I@kernel.org>
Date: Fri, 2 Jan 2026 18:31:38 +0200
From: Jarkko Sakkinen <jarkko@...nel.org>
To: James Bottomley <James.Bottomley@...senpartnership.com>
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>,
	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 Fri, Dec 19, 2025 at 03:54:47PM -0500, James Bottomley wrote:
> On Tue, 2025-12-16 at 11:21 +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.
> 
> Shouldn't that also be
> 
> Fixes: b7960b904861 ("tpm2-sessions: Open code tpm_buf_append_hmac_session()")

The implementation has pre-existed before that commit so it did
not really cause it. The call path was just more masked before
open coding it.

The code is of course exercised in !TCG_TPM2_HMAC case but it 
by definition does nothing.

> 
> > 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))
> 
> Since the statement above is that the if is always true, why do you
> still have it here?

This is still necessary for !TCG_TPM2_HMAC case. The commit is pretty
much exactly in its described scope.

> 
> Regards,
> 
> James
> 

BR, Jarkko