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Wed, 23 Oct 2024 17:38:29 GMT Received: from smtpav01.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1ECBA5805D; Wed, 23 Oct 2024 17:38:29 +0000 (GMT) Received: from smtpav01.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2B76158057; Wed, 23 Oct 2024 17:38:28 +0000 (GMT) Received: from [9.47.158.152] (unknown [9.47.158.152]) by smtpav01.dal12v.mail.ibm.com (Postfix) with ESMTP; Wed, 23 Oct 2024 17:38:28 +0000 (GMT) Message-ID: <5ba23b66-d5e7-49f4-a0ba-705b52184f96@linux.ibm.com> Date: Wed, 23 Oct 2024 13:38:27 -0400 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 2/5] tpm: Implement tpm2_load_null() rollback To: Jarkko Sakkinen , linux-integrity@vger.kernel.org, Peter Huewe , Jason Gunthorpe , James Bottomley Cc: David Howells , Mimi Zohar , Roberto Sassu , linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20241021053921.33274-1-jarkko@kernel.org> <20241021053921.33274-3-jarkko@kernel.org> Content-Language: en-US From: Stefan Berger In-Reply-To: <20241021053921.33274-3-jarkko@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: ieOeGiglLsYRpaQgOXo4ZXtXmBuLOg8E X-Proofpoint-GUID: 4d34dB0iMEKO8NPEy9TOa_mqMMDUte8i Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 suspectscore=0 phishscore=0 mlxlogscore=999 adultscore=0 spamscore=0 malwarescore=0 clxscore=1011 lowpriorityscore=0 bulkscore=0 mlxscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2409260000 definitions=main-2410230111 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 > -- > 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