| Message ID | 20241021053921.33274-3-jarkko@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Lazy flush for the auth session | expand |
On 10/21/24 1:39 AM, Jarkko Sakkinen wrote: > tpm2_load_null() has weak and broken error handling: > > - The return value of tpm2_create_primary() is ignored. > - Leaks TPM return codes from tpm2_load_context() to the caller. > - If the key name comparison succeeds returns previous error > instead of zero to the caller. > > Implement a proper error rollback. > > Cc: stable@vger.kernel.org # v6.10+ > Fixes: eb24c9788cd9 ("tpm: disable the TPM if NULL name changes") > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> > -- > v6: > - Address Stefan's remark: > https://lore.kernel.org/linux-integrity/def4ec2d-584b-405f-9d5e-99267013c3c0@linux.ibm.com/ > v5: > - Fix the TPM error code leak from tpm2_load_context(). > v4: > - No changes. > v3: > - Update log messages. Previously the log message incorrectly stated > on load failure that integrity check had been failed, even tho the > check is done *after* the load operation. > v2: > - Refined the commit message. > - Reverted tpm2_create_primary() changes. They are not required if > tmp_null_key is used as the parameter. > --- > drivers/char/tpm/tpm2-sessions.c | 43 +++++++++++++++++--------------- > 1 file changed, 23 insertions(+), 20 deletions(-) > > diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c > index 1e12e0b2492e..bdac11964b55 100644 > --- a/drivers/char/tpm/tpm2-sessions.c > +++ b/drivers/char/tpm/tpm2-sessions.c > @@ -915,33 +915,36 @@ 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"); > + rc = tpm2_create_primary(chip, TPM2_RH_NULL, &tmp_null_key, name); > + if (rc) > + goto err; > + > + /* 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; > + } > + > + /* Deduce from the name change TPM interference: */ > + dev_err(&chip->dev, "the null key integrity check failedh\n"); stray 'h': s/failedh/failed > + tpm2_flush_context(chip, tmp_null_key); > chip->flags |= TPM_CHIP_FLAG_DISABLE; > > - return rc; > +err: > + return rc ? -ENODEV : 0; > } > > /** Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c index 1e12e0b2492e..bdac11964b55 100644 --- a/drivers/char/tpm/tpm2-sessions.c +++ b/drivers/char/tpm/tpm2-sessions.c @@ -915,33 +915,36 @@ 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"); + rc = tpm2_create_primary(chip, TPM2_RH_NULL, &tmp_null_key, name); + if (rc) + goto err; + + /* 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; + } + + /* Deduce from the name change TPM interference: */ + dev_err(&chip->dev, "the null key integrity check failedh\n"); + tpm2_flush_context(chip, tmp_null_key); chip->flags |= TPM_CHIP_FLAG_DISABLE; - return rc; +err: + return rc ? -ENODEV : 0; } /**
tpm2_load_null() has weak and broken error handling: - The return value of tpm2_create_primary() is ignored. - Leaks TPM return codes from tpm2_load_context() to the caller. - If the key name comparison succeeds returns previous error instead of zero to the caller. Implement a proper error rollback. Cc: stable@vger.kernel.org # v6.10+ Fixes: eb24c9788cd9 ("tpm: disable the TPM if NULL name changes") Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> -- v6: - Address Stefan's remark: https://lore.kernel.org/linux-integrity/def4ec2d-584b-405f-9d5e-99267013c3c0@linux.ibm.com/ v5: - Fix the TPM error code leak from tpm2_load_context(). v4: - No changes. v3: - Update log messages. Previously the log message incorrectly stated on load failure that integrity check had been failed, even tho the check is done *after* the load operation. v2: - Refined the commit message. - Reverted tpm2_create_primary() changes. They are not required if tmp_null_key is used as the parameter. --- drivers/char/tpm/tpm2-sessions.c | 43 +++++++++++++++++--------------- 1 file changed, 23 insertions(+), 20 deletions(-)