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From: Mimi Zohar <zohar@linux.vnet.ibm.com>
To: linux-integrity@vger.kernel.org
Cc: Hans de Goede <hdegoede@redhat.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Peter Jones <pjones@redhat.com>,
	Mimi Zohar <zohar@linux.vnet.ibm.com>,
	linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org, David Howells <dhowells@redhat.com>,
	"Luis R . Rodriguez" <mcgrof@kernel.org>,
	"Luis R . Rodriguez" <mcgrof@suse.com>,
	Kees Cook <keescook@chromium.org>,
	"Serge E . Hallyn" <serge@hallyn.com>,
	Stephen Boyd <stephen.boyd@linaro.org>
Subject: [RFC PATCH 6/6] ima: prevent loading firmware into a pre-allocated buffer
Date: Tue,  1 May 2018 09:48:23 -0400	[thread overview]
Message-ID: <1525182503-13849-7-git-send-email-zohar@linux.vnet.ibm.com> (raw)
In-Reply-To: <1525182503-13849-1-git-send-email-zohar@linux.vnet.ibm.com>

Question: can the device access the pre-allocated buffer at any time?

By allowing devices to request firmware be loaded directly into a
pre-allocated buffer, will this allow the device access to the firmware
before the kernel has verified the firmware signature?

Is it dependent on the type of buffer allocated (eg. DMA)?  For example,
qcom_mdt_load() -> qcom_scm_pas_init_image() -> dma_alloc_coherent().

With an IMA policy requiring signed firmware, this patch would prevent
loading firmware into a pre-allocated buffer.

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Serge E. Hallyn <serge@hallyn.com>
Cc: Stephen Boyd <stephen.boyd@linaro.org>
---
 security/integrity/ima/ima_main.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index eb9c273ab81d..3098131f77c4 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -454,6 +454,15 @@ int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
 		return 0;
 	}
 
+	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;
+	}
+
 	if (read_id == READING_FIRMWARE_FALLBACK) {
 		if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
 		    (ima_appraise & IMA_APPRAISE_ENFORCE)) {
-- 
2.7.5

  parent reply	other threads:[~2018-05-01 13:49 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-01 13:48 [PATCH 0/6] firmware: kernel signature verification Mimi Zohar
2018-05-01 13:48 ` [PATCH 1/6] firmware: permit LSMs and IMA to fail firmware sysfs fallback loading Mimi Zohar
2018-05-04  0:02   ` Luis R. Rodriguez
2018-05-04  0:36     ` Mimi Zohar
2018-05-01 13:48 ` [PATCH 2/6] ima: prevent sysfs fallback firmware loading Mimi Zohar
2018-05-04  0:06   ` Luis R. Rodriguez
2018-05-01 13:48 ` [PATCH 3/6] firmware: differentiate between signed regulatory.db and other firmware Mimi Zohar
2018-05-04  0:07   ` Luis R. Rodriguez
2018-05-04  0:24     ` Mimi Zohar
2018-05-08 17:34       ` Luis R. Rodriguez
2018-05-09 11:30         ` Mimi Zohar
2018-05-09 19:15           ` Luis R. Rodriguez
2018-05-09 19:57             ` Mimi Zohar
2018-05-09 21:22               ` Luis R. Rodriguez
2018-05-09 22:06                 ` Mimi Zohar
2018-05-09 23:48                   ` Luis R. Rodriguez
2018-05-10  2:00                     ` Mimi Zohar
2018-05-10 23:26                       ` Luis R. Rodriguez
2018-05-11  5:00                         ` Mimi Zohar
2018-05-11 21:52                           ` Luis R. Rodriguez
2018-05-14 12:58                             ` Mimi Zohar
2018-05-14 19:28                               ` Luis R. Rodriguez
2018-05-15  2:02                                 ` Mimi Zohar
2018-05-15  3:26                                   ` Luis R. Rodriguez
2018-05-15 12:32                                     ` Josh Boyer
2018-05-15 12:43                                       ` Mimi Zohar
2018-05-01 13:48 ` [PATCH 4/6] ima: coordinate with signed regulatory.db Mimi Zohar
2018-05-01 13:48 ` [PATCH 5/6] ima: verify kernel firmware signatures when using a preallocated buffer Mimi Zohar
2018-05-01 13:48 ` Mimi Zohar [this message]
2018-05-04  0:10   ` [RFC PATCH 6/6] ima: prevent loading firmware into a pre-allocated buffer Luis R. Rodriguez

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