[PATCH ghak10 v5 1/2] audit: Add functions to log time adjustments

Ondrej Mosnacek
2018-08-24T12:00:00Z

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
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@redhat.com>
---
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