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@lin... Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions") Tested-by: Michael Ellerman mpe@ellerman.id.au # ppc Signed-off-by: Jarkko Sakkinen jarkko@kernel.org --- v4: * Added tested-by from Michael Ellerman. v3: * No changes. 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;