[PATCH v4 4/4] fanotify,audit: deliver fan_info as a hex-encoded string

[Richard Guy Briggs <rgb@xxxxxxxxxx>]

Currently the only type of fanotify info that is defined is an audit
rule number, but convert it to hex encoding to future-proof the field.

Sample record:
  type=FANOTIFY msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=3F

Suggested-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
---
 kernel/auditsc.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index f000fec52360..0f747015c577 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -2908,22 +2908,36 @@ void __audit_fanotify(u32 response, size_t len, char *buf)
 
 	if (!(len && buf)) {
 		audit_log(audit_context(), GFP_KERNEL, AUDIT_FANOTIFY,
-			  "resp=%u fan_type=0 fan_info=?", response);
+			  "resp=%u fan_type=0 fan_info=3F", response); /* "?" */
 		return;
 	}
 	while (c >= sizeof(struct fanotify_response_info_header)) {
+		struct audit_context *ctx = audit_context();
+		struct audit_buffer *ab;
+
 		friar = (struct fanotify_response_info_audit_rule *)buf;
 		switch (friar->hdr.type) {
 		case FAN_RESPONSE_INFO_AUDIT_RULE:
 			if (friar->hdr.len < sizeof(*friar)) {
-				audit_log(audit_context(), GFP_KERNEL, AUDIT_FANOTIFY,
-					  "resp=%u fan_type=%u fan_info=(incomplete)",
-					  response, friar->hdr.type);
+				ab = audit_log_start(ctx, GFP_KERNEL, AUDIT_FANOTIFY);
+				if (ab) {
+					audit_log_format(ab, "resp=%u fan_type=%u fan_info=",
+							 response, friar->hdr.type);
+#define INCOMPLETE "(incomplete)"
+					audit_log_n_hex(ab, INCOMPLETE, sizeof(INCOMPLETE));
+					audit_log_end(ab);
+				}
 				return;
 			}
-			audit_log(audit_context(), GFP_KERNEL, AUDIT_FANOTIFY,
-				  "resp=%u fan_type=%u fan_info=%u",
-				  response, friar->hdr.type, friar->audit_rule);
+			ab = audit_log_start(ctx, GFP_KERNEL, AUDIT_FANOTIFY);
+			if (ab) {
+				audit_log_format(ab, "resp=%u fan_type=%u fan_info=",
+						 response, friar->hdr.type);
+				audit_log_n_hex(ab, (char *)&friar->audit_rule,
+						sizeof(friar->audit_rule));
+				audit_log_end(ab);
+
+			}
 		}
 		c -= friar->hdr.len;
 		ib += friar->hdr.len;
-- 
2.27.0