[PATCH 3/4] tpm: address tpm2_create_primary() failure

[Jarkko Sakkinen]

tpm2_load_null() ignores the return value of tpm2_create_primary(). Return
instead on failure. On success when the null key name has not been changed
heal appropriately, and return the created key handle instead of flushing
it.

Fixes: eb24c9788cd9 ("tpm: disable the TPM if NULL name changes")
Signed-off-by: Jarkko Sakkinen <jar...@kernel.org>
---
 drivers/char/tpm/tpm2-sessions.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index d63510ad44ab..34ce0d9d4577 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -850,9 +850,10 @@ 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);
@@ -861,11 +862,17 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 
*null_key)
 
        /* 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 */
+
+       rc = tpm2_create_primary(chip, TPM2_RH_NULL, &tmp_null_key, name);
+       if (rc)
                return rc;
+
+       /* Return the null key if the name has not been changed: */
+       if (memcmp(name, chip->null_key_name, sizeof(name)) == 0) {
+               *null_key = tmp_null_key;
+               return 0;
+       }
+
        /*
         * Fatal TPM failure: the NULL seed has actually changed, so
         * the TPM must have been illegally reset.  All in-kernel TPM
@@ -874,6 +881,7 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 
*null_key)
         * userspace programmes can't be compromised by it.
         */
        dev_err(&chip->dev, "NULL name has changed, disabling TPM due to 
interference\n");
+       tpm2_flush_context(chip, tmp_null_key);
        chip->flags |= TPM_CHIP_FLAG_DISABLE;
 
        return rc;
@@ -991,10 +999,6 @@ static int tpm2_parse_create_primary(struct tpm_chip 
*chip, struct tpm_buf *buf,
        u32 val, param_len, keyhandle;
 
        keyhandle = tpm_buf_read_u32(buf, &offset_r);
-       if (handle)
-               *handle = keyhandle;
-       else
-               tpm2_flush_context(chip, keyhandle);
 
        param_len = tpm_buf_read_u32(buf, &offset_r);
        /*
@@ -1135,6 +1139,7 @@ static int tpm2_parse_create_primary(struct tpm_chip 
*chip, struct tpm_buf *buf,
                return -EINVAL;
        }
 
+       *handle = keyhandle;
        return 0;
 }
 
-- 
2.46.0