ntp: Split out timex validation from do_adjtimex

Split out the timex validation done in do_adjtimex into a separate
function. This will help simplify logic in following patches.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>

kernel/time/ntp.c

@@ -622,17 +622,13 @@ static inline void process_adjtimex_modes(struct timex *txc,
 		ntp_update_frequency();
 }
 
-/*
- * adjtimex mainly allows reading (and writing, if superuser) of
- * kernel time-keeping variables. used by xntpd.
+
+
+/**
+ * ntp_validate_timex - Ensures the timex is ok for use in do_adjtimex
  */
-int do_adjtimex(struct timex *txc)
+int ntp_validate_timex(struct timex *txc)
 {
-	struct timespec ts;
-	u32 time_tai, orig_tai;
-	int result;
-
-	/* Validate the data before disabling interrupts */
 	if (txc->modes & ADJ_ADJTIME) {
 		/* singleshot must not be used with any other mode bits */
 		if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
@@ -644,7 +640,6 @@ int do_adjtimex(struct timex *txc)
 		/* In order to modify anything, you gotta be super-user! */
 		 if (txc->modes && !capable(CAP_SYS_TIME))
 			return -EPERM;
-
 		/*
 		 * if the quartz is off by more than 10% then
 		 * something is VERY wrong!
@@ -655,12 +650,32 @@ int do_adjtimex(struct timex *txc)
 			return -EINVAL;
 	}
 
+	if ((txc->modes & ADJ_SETOFFSET) && (!capable(CAP_SYS_TIME)))
+		return -EPERM;
+
+	return 0;
+}
+
+
+/*
+ * adjtimex mainly allows reading (and writing, if superuser) of
+ * kernel time-keeping variables. used by xntpd.
+ */
+int do_adjtimex(struct timex *txc)
+{
+	struct timespec ts;
+	u32 time_tai, orig_tai;
+	int result;
+
+	/* Validate the data before disabling interrupts */
+	result = ntp_validate_timex(txc);
+	if (result)
+		return result;
+
 	if (txc->modes & ADJ_SETOFFSET) {
 		struct timespec delta;
 		delta.tv_sec  = txc->time.tv_sec;
 		delta.tv_nsec = txc->time.tv_usec;
-		if (!capable(CAP_SYS_TIME))
-			return -EPERM;
 		if (!(txc->modes & ADJ_NANO))
 			delta.tv_nsec *= 1000;
 		result = timekeeping_inject_offset(&delta);