[PATCH v8 04/17] integrity: Do not allow machine keyring updates following init

[Eric Snowberg]

The machine keyring is setup during init.  No additional keys should be
allowed to be added afterwards.  Leave the permission as read only.

Signed-off-by: Eric Snowberg <eric.snowberg@xxxxxxxxxx>
Reviewed-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
---
v2: Initial version
v4: Unmodified from v2
v5: Rename to machine keyring
v6: Add additional comment (suggested by Jarkko)
v7: Unmodified from v6
v8: Code unmodified from v7 added Mimi's Reviewed-by
---
 security/integrity/digsig.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
index 8c315be8ad99..910fe29a5037 100644
--- a/security/integrity/digsig.c
+++ b/security/integrity/digsig.c
@@ -140,7 +140,13 @@ int __init integrity_init_keyring(const unsigned int id)
 		return -ENOMEM;
 
 	restriction->check = restrict_link_to_ima;
-	perm |= KEY_USR_WRITE;
+
+	/*
+	 * No additional keys shall be allowed to load into the machine
+	 * keyring following init
+	 */
+	if (id != INTEGRITY_KEYRING_MACHINE)
+		perm |= KEY_USR_WRITE;
 
 out:
 	return __integrity_init_keyring(id, perm, restriction);
-- 
2.18.4