integrity: Add errno field in audit message

Error code is not included in the audit messages logged by
the integrity subsystem.

Define a new function integrity_audit_message() that takes error code
in the "errno" parameter. Add "errno" field in the audit messages logged
by the integrity subsystem and set the value passed in the "errno"
parameter.

[    6.303048] audit: type=1804 audit(1592506281.627:2): pid=1 uid=0 auid=4294967295 ses=4294967295 subj=kernel op=measuring_key cause=ENOMEM comm="swapper/0" name=".builtin_trusted_keys" res=0 errno=-12

[    7.987647] audit: type=1802 audit(1592506283.312:9): pid=1 uid=0 auid=4294967295 ses=4294967295 subj=system_u:system_r:init_t:s0 op=policy_update cause=completed comm="systemd" res=1 errno=0

[    8.019432] audit: type=1804 audit(1592506283.344:10): pid=1 uid=0 auid=4294967295 ses=4294967295 subj=system_u:system_r:init_t:s0 op=measuring_kexec_cmdline cause=hashing_error comm="systemd" name="kexec-cmdline" res=0 errno=-22

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Suggested-by: Steve Grubb <sgrubb@redhat.com>
Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

Author: nramas

security/integrity/integrity.h

@@ -239,6 +239,11 @@ void integrity_audit_msg(int audit_msgno, struct inode *inode,
 			 const unsigned char *fname, const char *op,
 			 const char *cause, int result, int info);
 
+void integrity_audit_message(int audit_msgno, struct inode *inode,
+			     const unsigned char *fname, const char *op,
+			     const char *cause, int result, int info,
+			     int errno);
+
 static inline struct audit_buffer *
 integrity_audit_log_start(struct audit_context *ctx, gfp_t gfp_mask, int type)
 {
@@ -253,6 +258,14 @@ static inline void integrity_audit_msg(int audit_msgno, struct inode *inode,
 {
 }
 
+static inline void integrity_audit_message(int audit_msgno,
+					   struct inode *inode,
+					   const unsigned char *fname,
+					   const char *op, const char *cause,
+					   int result, int info, int errno)
+{
+}
+
 static inline struct audit_buffer *
 integrity_audit_log_start(struct audit_context *ctx, gfp_t gfp_mask, int type)
 {

security/integrity/integrity_audit.c

@@ -28,6 +28,15 @@ __setup("integrity_audit=", integrity_audit_setup);
 void integrity_audit_msg(int audit_msgno, struct inode *inode,
 			 const unsigned char *fname, const char *op,
 			 const char *cause, int result, int audit_info)
+{
+	integrity_audit_message(audit_msgno, inode, fname, op, cause,
+				result, audit_info, 0);
+}
+
+void integrity_audit_message(int audit_msgno, struct inode *inode,
+			     const unsigned char *fname, const char *op,
+			     const char *cause, int result, int audit_info,
+			     int errno)
 {
 	struct audit_buffer *ab;
 	char name[TASK_COMM_LEN];
@@ -53,6 +62,6 @@ void integrity_audit_msg(int audit_msgno, struct inode *inode,
 		audit_log_untrustedstring(ab, inode->i_sb->s_id);
 		audit_log_format(ab, " ino=%lu", inode->i_ino);
 	}
-	audit_log_format(ab, " res=%d", !result);
+	audit_log_format(ab, " res=%d errno=%d", !result, errno);
 	audit_log_end(ab);
 }