[RFC PATCH v1] audit: log AUDIT_TIME_* records only from rules

[Richard Guy Briggs]

AUDIT_TIME_* events are generated when there are syscall rules present that are
not related to time keeping.  This will produce noisy log entries that could
flood the logs and hide events we really care about.

Rather than immediately produce the AUDIT_TIME_* records, store the data and
log it at syscall exit time respecting the filter rules.

Please see https://bugzilla.redhat.com/show_bug.cgi?id=1991919

Signed-off-by: Richard Guy Briggs <rgb at redhat.com>
---
Note: This is a quick and dirty proof-of-concept.  If this approach of
storing the values in the audit_context for later filtering is
acceptable I'll clean up the patch (re-name functions) and re-submit.

 kernel/audit.h   |  6 ++++++
 kernel/auditsc.c | 29 +++++++++++++++++++++++++----
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/kernel/audit.h b/kernel/audit.h
index 3b64a97f6091..25d63731b0e0 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -196,6 +196,12 @@ struct audit_context {
 		struct {
 			char			*name;
 		} module;
+		struct {
+			struct audit_ntp_data	data;
+		} ntp;
+		struct {
+			struct timespec64	injoffset;
+		} tk;
 	};
 	int fds[2];
 	struct audit_proctitle proctitle;
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 6efb0bb909d0..8983790ad86a 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1210,11 +1210,18 @@ static void audit_log_fcaps(struct audit_buffer *ab, struct audit_names *name)
 			 from_kuid(&init_user_ns, name->fcap.rootid));
 }
 
+void __audit_ntp_log_(const struct audit_ntp_data *ad);
+
 static void show_special(struct audit_context *context, int *call_panic)
 {
 	struct audit_buffer *ab;
 	int i;
 
+	if (context->type == AUDIT_TIME_ADJNTPVAL) {
+		__audit_ntp_log_(&context->ntp.data);
+		return;
+	}
+
 	ab = audit_log_start(context, GFP_KERNEL, context->type);
 	if (!ab)
 		return;
@@ -1324,6 +1331,11 @@ static void show_special(struct audit_context *context, int *call_panic)
 			audit_log_format(ab, "(null)");
 
 		break;
+	case AUDIT_TIME_INJOFFSET:
+		audit_log_format(ab, "sec=%lli nsec=%li",
+				 (long long)context->tk.injoffset.tv_sec,
+				 context->tk.injoffset.tv_nsec);
+		break;
 	}
 	audit_log_end(ab);
 }
@@ -2571,9 +2583,18 @@ void __audit_fanotify(unsigned int response)
 
 void __audit_tk_injoffset(struct timespec64 offset)
 {
-	audit_log(audit_context(), GFP_KERNEL, AUDIT_TIME_INJOFFSET,
-		  "sec=%lli nsec=%li",
-		  (long long)offset.tv_sec, offset.tv_nsec);
+	struct audit_context *context = audit_context();
+
+	context->type = AUDIT_TIME_INJOFFSET;
+	memcpy(&context->tk.injoffset, &offset, sizeof(offset));
+}
+
+void __audit_ntp_log(const struct audit_ntp_data *ad)
+{
+	struct audit_context *context = audit_context();
+
+	context->type = AUDIT_TIME_ADJNTPVAL;
+	memcpy(&context->ntp.data, ad, sizeof(*ad));
 }
 
 static void audit_log_ntp_val(const struct audit_ntp_data *ad,
@@ -2588,7 +2609,7 @@ static void audit_log_ntp_val(const struct audit_ntp_data *ad,
 		  "op=%s old=%lli new=%lli", op, val->oldval, val->newval);
 }
 
-void __audit_ntp_log(const struct audit_ntp_data *ad)
+void __audit_ntp_log_(const struct audit_ntp_data *ad)
 {
 	audit_log_ntp_val(ad, "offset",	AUDIT_NTP_OFFSET);
 	audit_log_ntp_val(ad, "freq",	AUDIT_NTP_FREQ);
-- 
2.27.0