[PATCH v2 7/9] ima: based on policy require signed firmware (sysfs fallback)

[Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>]

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

Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>
Cc: Luis R. Rodriguez <mcgrof@xxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Matthew Garrett <mjg59@xxxxxxxxxx>
---
 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 7e1a127f18fe..29d1a929af5c 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -451,7 +451,17 @@ int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
 		}
 		return 0;
 	}
+
+	if (read_id == READING_FIRMWARE_FALLBACK_SYSFS) {
+		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