[RFC PATCH ghak10 v4 1/2] audit: Add functions to log time adjustments

[Ondrej Mosnacek]

This patch adds two auxiliary record types that will be used to annotate
the adjtimex SYSCALL records with the NTP/timekeeping values that have
been changed.

Next, it adds two functions to the audit interface:
 - audit_tk_injoffset(), which will be called whenever a timekeeping
   offset is injected by a syscall from userspace,
 - audit_ntp_adjust(), which will be called whenever an NTP internal
   variable is changed by a syscall from userspace.

Quick reference for the fields of the new records:
    AUDIT_TIME_INJOFFSET
        sec - the 'seconds' part of the offset
        nsec - the 'nanoseconds' part of the offset
    AUDIT_TIME_ADJNTPVAL
        op - which value was adjusted:
            offset - corresponding to the time_offset variable
            freq   - corresponding to the time_freq variable
            status - corresponding to the time_status variable
            maxerr - corresponding to the time_maxerror variable
            esterr - corresponding to the time_esterror variable
            const  - corresponding to the time_constant variable
            adjust - corresponding to the time_adjust variable
            tick   - corresponding to the tick_usec variable
            tai    - corresponding to the timekeeping's TAI offset
        old - the old value
        new - the new value

Signed-off-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
---
 include/linux/audit.h      | 21 +++++++++++++++++++++
 include/uapi/linux/audit.h |  2 ++
 kernel/auditsc.c           | 15 +++++++++++++++
 3 files changed, 38 insertions(+)

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 9334fbef7bae..0d084d4b4042 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -26,6 +26,7 @@
 #include <linux/sched.h>
 #include <linux/ptrace.h>
 #include <uapi/linux/audit.h>
+#include <uapi/linux/timex.h>
 
 #define AUDIT_INO_UNSET ((unsigned long)-1)
 #define AUDIT_DEV_UNSET ((dev_t)-1)
@@ -356,6 +357,8 @@ extern void __audit_log_capset(const struct cred *new, const struct cred *old);
 extern void __audit_mmap_fd(int fd, int flags);
 extern void __audit_log_kern_module(char *name);
 extern void __audit_fanotify(unsigned int response);
+extern void __audit_tk_injoffset(struct timespec64 offset);
+extern void __audit_ntp_adjust(const char *type, s64 oldval, s64 newval);
 
 static inline void audit_ipc_obj(struct kern_ipc_perm *ipcp)
 {
@@ -458,6 +461,18 @@ static inline void audit_fanotify(unsigned int response)
 		__audit_fanotify(response);
 }
 
+static inline void audit_tk_injoffset(struct timespec64 offset)
+{
+	if (!audit_dummy_context())
+		__audit_tk_injoffset(offset);
+}
+
+static inline void audit_ntp_adjust(const char *type, s64 oldval, s64 newval)
+{
+	if (!audit_dummy_context())
+		__audit_ntp_adjust(type, oldval, newval);
+}
+
 extern int audit_n_rules;
 extern int audit_signals;
 #else /* CONFIG_AUDITSYSCALL */
@@ -584,6 +599,12 @@ static inline void audit_log_kern_module(char *name)
 static inline void audit_fanotify(unsigned int response)
 { }
 
+static inline void audit_tk_injoffset(struct timespec64 offset)
+{ }
+
+static inline void audit_ntp_adjust(const char *type, s64 oldval, s64 newval)
+{ }
+
 static inline void audit_ptrace(struct task_struct *t)
 { }
 #define audit_n_rules 0
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index 4e3eaba84175..242ce562b41a 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -114,6 +114,8 @@
 #define AUDIT_REPLACE		1329	/* Replace auditd if this packet unanswerd */
 #define AUDIT_KERN_MODULE	1330	/* Kernel Module events */
 #define AUDIT_FANOTIFY		1331	/* Fanotify access decision */
+#define AUDIT_TIME_INJOFFSET	1332	/* Timekeeping offset injected */
+#define AUDIT_TIME_ADJNTPVAL	1333	/* NTP value adjustment */
 
 #define AUDIT_AVC		1400	/* SE Linux avc denial or grant */
 #define AUDIT_SELINUX_ERR	1401	/* Internal SE Linux Errors */
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index fb207466e99b..d355d32d9765 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -2422,6 +2422,21 @@ void __audit_fanotify(unsigned int response)
 		AUDIT_FANOTIFY,	"resp=%u", response);
 }
 
+/* We need to allocate with GFP_ATOMIC here, since these two functions will be
+ * called while holding the timekeeping lock: */
+void __audit_tk_injoffset(struct timespec64 offset)
+{
+	audit_log(audit_context(), GFP_ATOMIC, AUDIT_TIME_INJOFFSET,
+		  "sec=%lli nsec=%li", (long long)offset.tv_sec, offset.tv_nsec);
+}
+
+void __audit_ntp_adjust(const char *type, s64 oldval, s64 newval)
+{
+	audit_log(audit_context(), GFP_ATOMIC, AUDIT_TIME_ADJNTPVAL,
+		  "op=%s old=%lli new=%lli", type,
+		  (long long)oldval, (long long)newval);
+}
+
 static void audit_log_task(struct audit_buffer *ab)
 {
 	kuid_t auid, uid;
-- 
2.17.1