Re: [PATCH 1/4] tpm: Use -EPERM as fallback error code in tpm_ret_to_err

[Jonathan McDowell <noodles@earth.li>]

On Mon, Sep 22, 2025 at 07:43:14PM +0300, Jarkko Sakkinen wrote:
>From: Jarkko Sakkinen <jarkko.sakkinen@opinsys.com>
>
>Using -EFAULT here was not the best idea for tpm_ret_to_err as the fallback
>error code as it is no concise with trusted keys.
>
>Change the fallback as -EPERM, process TPM_RC_HASH also in tpm_ret_to_err,
>and by these changes make the helper applicable for trusted keys.
>
>Fixes: 539fbab37881 ("tpm: Mask TPM RC in tpm2_start_auth_session()")
>Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@opinsys.com>
>---
> include/linux/tpm.h                       |  9 +++++---
> security/keys/trusted-keys/trusted_tpm2.c | 26 ++++++-----------------
> 2 files changed, 13 insertions(+), 22 deletions(-)
>
>diff --git a/include/linux/tpm.h b/include/linux/tpm.h
>index dc0338a783f3..667d290789ca 100644
>--- a/include/linux/tpm.h
>+++ b/include/linux/tpm.h
>@@ -449,13 +449,16 @@ static inline ssize_t tpm_ret_to_err(ssize_t ret)
> 	if (ret < 0)
> 		return ret;
>
>-	switch (tpm2_rc_value(ret)) {
>-	case TPM2_RC_SUCCESS:
>+	if (!ret)
> 		return 0;

Fold this into the check above to get:

	if (ret <= 0)

?

>+
>+	switch (tpm2_rc_value(ret)) {
> 	case TPM2_RC_SESSION_MEMORY:
> 		return -ENOMEM;
>+	case TPM2_RC_HASH:
>+		return -EINVAL;
> 	default:
>-		return -EFAULT;
>+		return -EPERM;
> 	}
> }
>
>diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
>index 024be262702f..e165b117bbca 100644
>--- a/security/keys/trusted-keys/trusted_tpm2.c
>+++ b/security/keys/trusted-keys/trusted_tpm2.c
>@@ -348,25 +348,19 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
> 	}
>
> 	blob_len = tpm2_key_encode(payload, options, &buf.data[offset], blob_len);
>+	if (blob_len < 0)
>+		rc = blob_len;
>
> out:
> 	tpm_buf_destroy(&sized);
> 	tpm_buf_destroy(&buf);
>
>-	if (rc > 0) {
>-		if (tpm2_rc_value(rc) == TPM2_RC_HASH)
>-			rc = -EINVAL;
>-		else
>-			rc = -EPERM;
>-	}
>-	if (blob_len < 0)
>-		rc = blob_len;
>-	else
>+	if (!rc)
> 		payload->blob_len = blob_len;
>
> out_put:
> 	tpm_put_ops(chip);
>-	return rc;
>+	return tpm_ret_to_err(rc);
> }
>
> /**
>@@ -468,10 +462,7 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
> 		kfree(blob);
> 	tpm_buf_destroy(&buf);
>
>-	if (rc > 0)
>-		rc = -EPERM;
>-
>-	return rc;
>+	return tpm_ret_to_err(rc);
> }
>
> /**
>@@ -534,8 +525,6 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
> 	tpm_buf_fill_hmac_session(chip, &buf);
> 	rc = tpm_transmit_cmd(chip, &buf, 6, "unsealing");
> 	rc = tpm_buf_check_hmac_response(chip, &buf, rc);
>-	if (rc > 0)
>-		rc = -EPERM;
>
> 	if (!rc) {
> 		data_len = be16_to_cpup(
>@@ -568,7 +557,7 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
>
> out:
> 	tpm_buf_destroy(&buf);
>-	return rc;
>+	return tpm_ret_to_err(rc);
> }
>
> /**
>@@ -600,6 +589,5 @@ int tpm2_unseal_trusted(struct tpm_chip *chip,
>
> out:
> 	tpm_put_ops(chip);
>-
>-	return rc;
>+	return tpm_ret_to_err(rc);
> }
>-- 
>2.39.5
>
>

J.

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