On Tue, Jul 16, 2024 at 09:52:24PM +0300, Jarkko Sakkinen wrote:
> tpm_buf_append_name() has the following snippet in the beginning:
>
> if (!tpm2_chip_auth(chip)) {
> tpm_buf_append_u32(buf, handle);
> /* count the number of handles in the upper bits of flags */
> buf->handles++;
> return;
> }
>
> The claim in the comment is wrong, and the comment is in the wrong place
> as alignment in this case should not anyway be a concern of the call
> site. In essence the comment is lying about the code, and thus needs to
> be adressed.
>
> Further, 'handles' was incorrectly place to struct tpm_buf, as tpm-buf.c
> does manage its state. It is easy to grep that only piece of code that
> actually uses the field is tpm2-sessions.c.
>
> Address the issues by moving the variable to struct tpm_chip.
>
> Cc: stable@xxxxxxxxxxxxxxx # v6.10+
> Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
> Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
>
> v3:
> * Reset chip->handles in the beginning of tpm2_start_auth_session()
> so that it shows correct value, when TCG_TPM2_HMAC is enabled but
> tpm2_sessions_init() has never been called.
> v2:
> * Was a bit more broken than I first thought, as 'handles' is only
> useful for tpm2-sessions.c and has zero relation to tpm-buf.c.
> ---
> drivers/char/tpm/tpm-buf.c | 1 -
> drivers/char/tpm/tpm2-cmd.c | 2 +-
> drivers/char/tpm/tpm2-sessions.c | 7 ++++---
> include/linux/tpm.h | 8 ++++----
> 4 files changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> index cad0048bcc3c..d06e8e063151 100644
> --- a/drivers/char/tpm/tpm-buf.c
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -44,7 +44,6 @@ void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
> head->tag = cpu_to_be16(tag);
> head->length = cpu_to_be32(sizeof(*head));
> head->ordinal = cpu_to_be32(ordinal);
> - buf->handles = 0;
> }
> EXPORT_SYMBOL_GPL(tpm_buf_reset);
>
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index 1e856259219e..b781e4406fc2 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -776,7 +776,7 @@ int tpm2_auto_startup(struct tpm_chip *chip)
> if (rc)
> goto out;
>
> - rc = tpm2_sessions_init(chip);
> + /* rc = tpm2_sessions_init(chip); */
Left over from testing? Or should be removed entirely?
> out:
> /*
> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> index d3521aadd43e..5e7c12d64ba8 100644
> --- a/drivers/char/tpm/tpm2-sessions.c
> +++ b/drivers/char/tpm/tpm2-sessions.c
> @@ -238,8 +238,7 @@ void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
>
> if (!tpm2_chip_auth(chip)) {
> tpm_buf_append_u32(buf, handle);
> - /* count the number of handles in the upper bits of flags */
> - buf->handles++;
> + chip->handles++;
> return;
> }
>
> @@ -310,7 +309,7 @@ void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
>
> if (!tpm2_chip_auth(chip)) {
> /* offset tells us where the sessions area begins */
> - int offset = buf->handles * 4 + TPM_HEADER_SIZE;
> + int offset = chip->handles * 4 + TPM_HEADER_SIZE;
> u32 len = 9 + passphrase_len;
>
> if (tpm_buf_length(buf) != offset) {
> @@ -963,6 +962,8 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
> int rc;
> u32 null_key;
>
> + chip->handles = 0;
> +
> if (!auth) {
> dev_warn_once(&chip->dev, "auth session is not active\n");
> return 0;
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index e93ee8d936a9..b664f7556494 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -202,9 +202,9 @@ struct tpm_chip {
> /* active locality */
> int locality;
>
> + /* handle count for session: */
> + u8 handles;
> #ifdef CONFIG_TCG_TPM2_HMAC
> - /* details for communication security via sessions */
> -
> /* saved context for NULL seed */
> u8 null_key_context[TPM2_MAX_CONTEXT_SIZE];
> /* name of NULL seed */
> @@ -377,7 +377,6 @@ struct tpm_buf {
> u32 flags;
> u32 length;
> u8 *data;
> - u8 handles;
> };
>
> enum tpm2_object_attributes {
> @@ -517,7 +516,7 @@ static inline void tpm_buf_append_hmac_session_opt(struct tpm_chip *chip,
> if (tpm2_chip_auth(chip)) {
> tpm_buf_append_hmac_session(chip, buf, attributes, passphrase, passphraselen);
> } else {
> - offset = buf->handles * 4 + TPM_HEADER_SIZE;
> + offset = chip->handles * 4 + TPM_HEADER_SIZE;
> head = (struct tpm_header *)buf->data;
>
> /*
> @@ -541,6 +540,7 @@ void tpm2_end_auth_session(struct tpm_chip *chip);
>
> static inline int tpm2_start_auth_session(struct tpm_chip *chip)
> {
> + chip->handles = 0;
> return 0;
> }
> static inline void tpm2_end_auth_session(struct tpm_chip *chip)
> --
> 2.45.2
J.
--
"I'm not anti-establishment, I just don't see the point." -- Matthew
Kirkwood, OxLUG mailing list.
