[PATCH v2 1/3] tpm: Address !chip->auth in tpm2_*_auth_session()

Jarkko Sakkinen
2024-07-03T18:25:06Z

Unless tpm_chip_bootstrap() was called by the driver, !chip->auth can cause
a null derefence in tpm2_*_auth_session(). Thus, address !chip->auth in
tpm2_*_auth_session().

Cc: stable@vger.kernel.org # v6.9+
Reported-by: Stefan Berger <stefanb@linux.ibm.com>
Closes: https://lore.kernel.org/linux-integrity/20240617193408.1234365-1-stefanb@linux.ibm.com/
Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v2:
- Use dev_warn_once() instead of pr_warn_once().
---
drivers/char/tpm/tpm2-sessions.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 907ac9956a78..2f1d96a5a5a7 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -824,8 +824,13 @@ EXPORT_SYMBOL(tpm_buf_check_hmac_response);
*/
void tpm2_end_auth_session(struct tpm_chip *chip)
{
- tpm2_flush_context(chip, chip->auth->handle);
- memzero_explicit(chip->auth, sizeof(*chip->auth));
+ struct tpm2_auth *auth = chip->auth;
+
+ if (!auth)
+ return;
+
+ tpm2_flush_context(chip, auth->handle);
+ memzero_explicit(auth, sizeof(*auth));
}
EXPORT_SYMBOL(tpm2_end_auth_session);

@@ -907,6 +912,11 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
int rc;
u32 null_key;

+ if (!auth) {
+ dev_warn_once(&chip->dev, "auth session is not active\n");
+ return 0;
+ }
+
rc = tpm2_load_null(chip, &null_key);
if (rc)
goto out;
--
2.45.2