linux-kernel - [PATCH 2/6] ima: prevent sysfs fallback firmware loading

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Date:   Tue,  1 May 2018 09:48:19 -0400
From:   Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:     linux-integrity@...r.kernel.org
Cc:     Hans de Goede <hdegoede@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Peter Jones <pjones@...hat.com>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, David Howells <dhowells@...hat.com>,
        "Luis R . Rodriguez" <mcgrof@...nel.org>,
        "Luis R . Rodriguez" <mcgrof@...e.com>,
        Matthew Garrett <mjg59@...gle.com>
Subject: [PATCH 2/6] ima: prevent sysfs fallback firmware loading

With an IMA policy requiring signed firmware, this patch prevents
the sysfs fallback method of loading firmware.

Signed-off-by: Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc: Luis R. Rodriguez <mcgrof@...e.com>
Cc: David Howells <dhowells@...hat.com>
Cc: Matthew Garrett <mjg59@...gle.com>
---
 security/integrity/ima/ima_main.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 754ece08e1c6..8759280dccf6 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -453,7 +453,17 @@ int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
 		}
 		return 0;
 	}
+
+	if (read_id == READING_FIRMWARE_FALLBACK) {
+		if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
+		    (ima_appraise & IMA_APPRAISE_ENFORCE)) {
+			pr_err("Prevent firmware sysfs fallback loading.\n");
+			return -EACCES;
+		}
+		return 0;
+	}
 	return 0;
+
 }
 
 static int read_idmap[READING_MAX_ID] = {
-- 
2.7.5