ima: Add digest and digest_len params to the functions to measure a buffer

This patch performs the final modification necessary to pass the buffer
measurement to callers, so that they provide a functionality similar to
ima_file_hash(). It adds the 'digest' and 'digest_len' parameters to
ima_measure_critical_data() and process_buffer_measurement().

These functions calculate the digest even if there is no suitable rule in
the IMA policy and, in this case, they simply return 1 before generating a
new measurement entry.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
diff --git a/security/selinux/ima.c b/security/selinux/ima.c
index 34d4218..727c4e4 100644
--- a/security/selinux/ima.c
+++ b/security/selinux/ima.c
@@ -86,7 +86,8 @@ void selinux_ima_measure_state_locked(struct selinux_state *state)
 	}
 
 	ima_measure_critical_data("selinux", "selinux-state",
-				  state_str, strlen(state_str), false);
+				  state_str, strlen(state_str), false,
+				  NULL, 0);
 
 	kfree(state_str);
 
@@ -103,7 +104,8 @@ void selinux_ima_measure_state_locked(struct selinux_state *state)
 	}
 
 	ima_measure_critical_data("selinux", "selinux-policy-hash",
-				  policy, policy_len, true);
+				  policy, policy_len, true,
+				  NULL, 0);
 
 	vfree(policy);
 }