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Mon, 12 Feb 2024 20:28:42 GMT Received: from smtpav06.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7FD7C5805D; Mon, 12 Feb 2024 20:28:38 +0000 (GMT) Received: from smtpav06.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9BE8E58055; Mon, 12 Feb 2024 20:28:34 +0000 (GMT) Received: from [9.47.158.152] (unknown [9.47.158.152]) by smtpav06.dal12v.mail.ibm.com (Postfix) with ESMTP; Mon, 12 Feb 2024 20:28:34 +0000 (GMT) Message-ID: <7940b9d0-3133-4b08-b397-ad9ee34e3b34@linux.ibm.com> Date: Mon, 12 Feb 2024 15:28:33 -0500 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 19/25] integrity: Move integrity_kernel_module_request() to IMA Content-Language: en-US To: Paul Moore Cc: Roberto Sassu , viro@zeniv.linux.org.uk, brauner@kernel.org, chuck.lever@oracle.com, jlayton@kernel.org, neilb@suse.de, kolga@netapp.com, Dai.Ngo@oracle.com, tom@talpey.com, jmorris@namei.org, serge@hallyn.com, zohar@linux.ibm.com, dmitry.kasatkin@gmail.com, eric.snowberg@oracle.com, dhowells@redhat.com, jarkko@kernel.org, stephen.smalley.work@gmail.com, eparis@parisplace.org, casey@schaufler-ca.com, shuah@kernel.org, mic@digikod.net, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org, keyrings@vger.kernel.org, selinux@vger.kernel.org, linux-kselftest@vger.kernel.org, Roberto Sassu References: <20240115181809.885385-1-roberto.sassu@huaweicloud.com> <20240115181809.885385-20-roberto.sassu@huaweicloud.com> From: Stefan Berger In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: IG8gA7VCiIuoNiLherBpxii_bnuMc-F5 X-Proofpoint-ORIG-GUID: n2O60wZIGE2TuBwcELMLALmk7ji0iQ_T X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2024-02-12_16,2024-02-12_03,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 mlxscore=0 malwarescore=0 phishscore=0 impostorscore=0 bulkscore=0 lowpriorityscore=0 adultscore=0 clxscore=1015 spamscore=0 mlxlogscore=999 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311290000 definitions=main-2402120158 On 2/12/24 12:56, Paul Moore wrote: > On Mon, Feb 12, 2024 at 12:48 PM Stefan Berger wrote: >> On 1/15/24 13:18, Roberto Sassu wrote: > > ... > >>> +/** >>> + * ima_kernel_module_request - Prevent crypto-pkcs1pad(rsa,*) requests >>> + * @kmod_name: kernel module name >>> + * >>> + * We have situation, when public_key_verify_signature() in case of RSA > + * algorithm use alg_name to store internal information in order to >>> + * construct an algorithm on the fly, but crypto_larval_lookup() will try >>> + * to use alg_name in order to load kernel module with same name. >>> + * Since we don't have any real "crypto-pkcs1pad(rsa,*)" kernel modules, >>> + * we are safe to fail such module request from crypto_larval_lookup(). >>> + * >>> + * In this way we prevent modprobe execution during digsig verification >>> + * and avoid possible deadlock if modprobe and/or it's dependencies >>> + * also signed with digsig. >> >> This text needs to some reformulation at some point.. > > There is no time like the present. If you have a suggestion I would > love to hear it and I'm sure Roberto would too. > My interpretation of the issue after possibly lossy decoding of the above sentences: Avoid a deadlock by rejecting a virtual kernel module with the name "crypto-pkcs1pad(rsa,*)". This module may be requested by crypto_larval_lookup() while trying to verify an RSA signature in public_key_verify_signature(). Since the loading of the RSA module may itself cause the request for an RSA signature verification it will otherwise lead to a deadlock.