apparmor: fix module parameters can be changed after policy is locked

the policy_lock parameter is a one way switch that prevents policy
from being further modified. Unfortunately some of the module parameters
can effectively modify policy by turning off enforcement.

split policy_admin_capable into a view check and a full admin check,
and update the admin check to test the policy_lock parameter.

Signed-off-by: John Johansen <john.johansen@canonical.com>

1 files changed, 17 insertions, 1 deletions

diff --git a/security/apparmor/policy.c b/security/apparmor/policy.c
index 7807125..179e68d 100644
--- a/security/apparmor/policy.c
+++ b/security/apparmor/policy.c
@@ -918,6 +918,22 @@ static int audit_policy(int op, gfp_t gfp, const char *name, const char *info,
 			&sa, NULL);
 }
 
+bool policy_view_capable(void)
+{
+	struct user_namespace *user_ns = current_user_ns();
+	bool response = false;
+
+	if (ns_capable(user_ns, CAP_MAC_ADMIN))
+		response = true;
+
+	return response;
+}
+
+bool policy_admin_capable(void)
+{
+	return policy_view_capable() && !aa_g_lock_policy;
+}
+
 /**
  * aa_may_manage_policy - can the current task manage policy
  * @op: the policy manipulation operation being done
@@ -932,7 +948,7 @@ bool aa_may_manage_policy(int op)
 		return 0;
 	}
 
-	if (!capable(CAP_MAC_ADMIN)) {
+	if (!policy_admin_capable()) {
 		audit_policy(op, GFP_KERNEL, NULL, "not policy admin", -EACCES);
 		return 0;
 	}