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@xxxxxxxxxxxxxxx # v6.10+
Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
Reported-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@xxxxxxxxxxxxxxxxxxx/
Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
---
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?
Thanks,
Stefano
+ switch (rc) {
+ case TPM2_RC_SESSION_MEMORY:
+ rc = -ENOMEM;
+ goto out;
+ default:
+ rc = -EFAULT;
+ goto out;
+ }
+ }
+
if (rc == TPM2_RC_SUCCESS) {
chip->auth = auth;
return 0;
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 6c3125300c00..c1d3d60b416f 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -257,6 +257,7 @@ enum tpm2_return_codes {
TPM2_RC_TESTING = 0x090A, /* RC_WARN */
TPM2_RC_REFERENCE_H0 = 0x0910,
TPM2_RC_RETRY = 0x0922,
+ TPM2_RC_SESSION_MEMORY = 0x0903,
};
enum tpm2_command_codes {
--
2.39.5
