On Mon, Apr 07, 2025 at 10:04:09AM +0200, Stefano Garzarella wrote:
On Mon, Apr 07, 2025 at 10:20:57AM +0300, Jarkko Sakkinen wrote:
tpm2_start_auth_session() does not mask TPM RC correctly from the callers:
[ 28.766528] tpm tpm0: A TPM error (2307) occurred start auth session
Process TPM RCs inside tpm2_start_auth_session(), and map them to POSIX error codes.
Cc: stable@vger.kernel.org # v6.10+ Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions") Reported-by: Herbert Xu herbert@gondor.apana.org.au Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@gondor.apana.org.au... Signed-off-by: Jarkko Sakkinen jarkko@kernel.org
v3:
- rc > 0
v2:
- Investigate TPM rc only after destroying tpm_buf.
drivers/char/tpm/tpm2-sessions.c | 31 +++++++++++++++++-------------- include/linux/tpm.h | 1 + 2 files changed, 18 insertions(+), 14 deletions(-)
diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c index 3f89635ba5e8..abd54fb0a45a 100644 --- a/drivers/char/tpm/tpm2-sessions.c +++ b/drivers/char/tpm/tpm2-sessions.c @@ -40,11 +40,6 @@
- These are the usage functions:
- tpm2_start_auth_session() which allocates the opaque auth structure
- and gets a session from the TPM. This must be called before
- any of the following functions. The session is protected by a
- session_key which is derived from a random salt value
- encrypted to the NULL seed.
- tpm2_end_auth_session() kills the session and frees the resources.
- Under normal operation this function is done by
- tpm_buf_check_hmac_response(), so this is only to be used on
@@ -963,16 +958,13 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key) }
/**
- tpm2_start_auth_session() - create a HMAC authentication session with the TPM
- @chip: the TPM chip structure to create the session with
- tpm2_start_auth_session() - Create an a HMAC authentication session
- @chip: A TPM chip
- This function loads the NULL seed from its saved context and starts
- an authentication session on the null seed, fills in the
- @chip->auth structure to contain all the session details necessary
- for performing the HMAC, encrypt and decrypt operations and
- returns. The NULL seed is flushed before this function returns.
- Loads the ephemeral key (null seed), and starts an HMAC authenticated
- session. The null seed is flushed before the return.
- Return: zero on success or actual error encountered.
- Returns zero on success, or a POSIX error code.
*/ int tpm2_start_auth_session(struct tpm_chip *chip) { @@ -1024,7 +1016,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip) /* hash algorithm for session */ tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
- rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
rc = tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession"); tpm2_flush_context(chip, null_key);
if (rc == TPM2_RC_SUCCESS)
@@ -1032,6 +1024,17 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
tpm_buf_destroy(&buf);
- if (rc > 0) {
To avoid the nesting blocks, can we include `TPM2_RC_SUCCESS` case in the switch or move the `if (rc == TPM2_RC_SUCCESS)` before it?
What do you mean by "avoiding nesting blocks"?
Thanks, Stefano
BR, Jarkko