tpm: Rollback tpm2_load_null()

Do not continue on tpm2_create_primary() failure in tpm2_load_null().

Cc: stable@vger.kernel.org # v6.10+
Fixes: eb24c9788cd9 ("tpm: disable the TPM if NULL name changes")
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index bb7b94b32c46a7dd3c461182ce977e6ed9c11af3..4821be27667062fbd5304d8416b0ee059ac197e7 100644 (file)
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -915,33 +915,37 @@ static int tpm2_parse_start_auth_session(struct tpm2_auth *auth,
 
 static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
 {
-       int rc;
        unsigned int offset = 0; /* dummy offset for null seed context */
        u8 name[SHA256_DIGEST_SIZE + 2];
+       u32 tmp_null_key;
+       int rc;
 
        rc = tpm2_load_context(chip, chip->null_key_context, &offset,
-                              null_key);
-       if (rc != -EINVAL)
-               return rc;
+                              &tmp_null_key);
+       if (rc != -EINVAL) {
+               if (!rc)
+                       *null_key = tmp_null_key;
+               goto err;
+       }
 
-       /* an integrity failure may mean the TPM has been reset */
-       dev_err(&chip->dev, "NULL key integrity failure!\n");
-       /* check the null name against what we know */
-       tpm2_create_primary(chip, TPM2_RH_NULL, NULL, name);
-       if (memcmp(name, chip->null_key_name, sizeof(name)) == 0)
-               /* name unchanged, assume transient integrity failure */
-               return rc;
-       /*
-        * Fatal TPM failure: the NULL seed has actually changed, so
-        * the TPM must have been illegally reset.  All in-kernel TPM
-        * operations will fail because the NULL primary can't be
-        * loaded to salt the sessions, but disable the TPM anyway so
-        * userspace programmes can't be compromised by it.
-        */
-       dev_err(&chip->dev, "NULL name has changed, disabling TPM due to interference\n");
+       /* Try to re-create null key, given the integrity failure: */
+       rc = tpm2_create_primary(chip, TPM2_RH_NULL, &tmp_null_key, name);
+       if (rc)
+               goto err;
+
+       /* Return null key if the name has not been changed: */
+       if (!memcmp(name, chip->null_key_name, sizeof(name))) {
+               *null_key = tmp_null_key;
+               return 0;
+       }
+
+       /* Deduce from the name change TPM interference: */
+       dev_err(&chip->dev, "null key integrity check failed\n");
+       tpm2_flush_context(chip, tmp_null_key);
        chip->flags |= TPM_CHIP_FLAG_DISABLE;
 
-       return rc;
+err:
+       return rc ? -ENODEV : 0;
 }
 
 /**