From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1fNixK-00007J-Ux for kexec@lists.infradead.org; Tue, 29 May 2018 18:02:57 +0000 Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w4THscfh091918 for ; Tue, 29 May 2018 14:02:36 -0400 Received: from e06smtp10.uk.ibm.com (e06smtp10.uk.ibm.com [195.75.94.106]) by mx0a-001b2d01.pphosted.com with ESMTP id 2j98k79ggt-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 29 May 2018 14:02:35 -0400 Received: from localhost by e06smtp10.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 29 May 2018 19:02:30 +0100 From: Mimi Zohar Subject: [RFC PATCH v4 7/8] ima: based on policy prevent loading firmware (pre-allocated buffer) Date: Tue, 29 May 2018 14:01:59 -0400 In-Reply-To: <1527616920-5415-1-git-send-email-zohar@linux.vnet.ibm.com> References: <1527616920-5415-1-git-send-email-zohar@linux.vnet.ibm.com> Message-Id: <1527616920-5415-8-git-send-email-zohar@linux.vnet.ibm.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: linux-integrity@vger.kernel.org Cc: Andres Rodriguez , Kees Cook , Ard Biesheuvel , Stephen Boyd , Greg Kroah-Hartman , "Luis R . Rodriguez" , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, David Howells , linux-security-module@vger.kernel.org, Eric Biederman , "Serge E . Hallyn" , Mimi Zohar , "Luis R . Rodriguez" Some systems are memory constrained but they need to load very large firmwares. The firmware subsystem allows drivers to request this firmware be loaded from the filesystem, but this requires that the entire firmware be loaded into kernel memory first before it's provided to the driver. This can lead to a situation where we map the firmware twice, once to load the firmware into kernel memory and once to copy the firmware into the final resting place. To resolve this problem, commit a098ecd2fa7d ("firmware: support loading into a pre-allocated buffer") introduced request_firmware_into_buf() API that allows drivers to request firmware be loaded directly into a pre-allocated buffer. The QCOM_MDT_LOADER calls dma_alloc_coherent() to allocate this buffer. According to Documentation/DMA-API.txt, Consistent memory is memory for which a write by either the device or the processor can immediately be read by the processor or device without having to worry about caching effects. (You may however need to make sure to flush the processor's write buffers before telling devices to read that memory.) Devices using pre-allocated DMA memory run the risk of the firmware being accessible by the device prior to the kernel's firmware signature verification has completed. Loading firmware already calls the security_kernel_read_file LSM hook. With an IMA policy requiring signed firmware, this patch prevents loading firmware into a pre-allocated buffer. Signed-off-by: Mimi Zohar Cc: Luis R. Rodriguez Cc: David Howells Cc: Kees Cook Cc: Serge E. Hallyn Cc: Stephen Boyd --- security/integrity/ima/ima_main.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-) diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index 4a87f78098c8..3dae605a1604 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -419,6 +419,15 @@ void ima_post_path_mknod(struct dentry *dentry) iint->flags |= IMA_NEW_FILE; } +static int read_idmap[READING_MAX_ID] = { + [READING_FIRMWARE] = FIRMWARE_CHECK, + [READING_FIRMWARE_PREALLOC_BUFFER] = FIRMWARE_CHECK, + [READING_MODULE] = MODULE_CHECK, + [READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK, + [READING_KEXEC_INITRAMFS] = KEXEC_INITRAMFS_CHECK, + [READING_POLICY] = POLICY_CHECK +}; + /** * ima_read_file - pre-measure/appraise hook decision based on policy * @file: pointer to the file to be measured/appraised/audit @@ -442,18 +451,17 @@ int ima_read_file(struct file *file, enum kernel_read_file_id read_id) } return 0; /* We rely on module signature checking */ } + + if (read_id == READING_FIRMWARE_PREALLOC_BUFFER) { + if ((ima_appraise & IMA_APPRAISE_FIRMWARE) && + (ima_appraise & IMA_APPRAISE_ENFORCE)) { + pr_err("Prevent device from accessing firmware prior to verifying the firmware signature.\n"); + return -EACCES; + } + } return 0; } -static int read_idmap[READING_MAX_ID] = { - [READING_FIRMWARE] = FIRMWARE_CHECK, - [READING_FIRMWARE_PREALLOC_BUFFER] = FIRMWARE_CHECK, - [READING_MODULE] = MODULE_CHECK, - [READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK, - [READING_KEXEC_INITRAMFS] = KEXEC_INITRAMFS_CHECK, - [READING_POLICY] = POLICY_CHECK -}; - /** * ima_post_read_file - in memory collect/appraise/audit measurement * @file: pointer to the file to be measured/appraised/audit -- 2.7.5 _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec