Revert "time: Handle negative seconds correctly in timespec64_to_ns()"

This reverts commit 528521f which is
commit 39ff83f upstream.

Arnd reports that this needs more review before being merged into all of
the trees.

Link: https://lore.kernel.org/r/CAK8P3a0z5jE=Z3Ps5bFTCFT7CHZR1JQ8VhdntDJAfsUxSPCcEw@mail.gmail.com
Reported-by: Arnd Bergmann <arnd@kernel.org>
Cc: Lukas Hannen <lukas.hannen@opensource.tttech-industrial.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/time64.h

@@ -25,9 +25,7 @@ struct itimerspec64 {
 #define TIME64_MIN			(-TIME64_MAX - 1)
 
 #define KTIME_MAX			((s64)~((u64)1 << 63))
-#define KTIME_MIN			(-KTIME_MAX - 1)
 #define KTIME_SEC_MAX			(KTIME_MAX / NSEC_PER_SEC)
-#define KTIME_SEC_MIN			(KTIME_MIN / NSEC_PER_SEC)
 
 /*
  * Limits for settimeofday():
@@ -126,13 +124,10 @@ static inline bool timespec64_valid_settod(const struct timespec64 *ts)
  */
 static inline s64 timespec64_to_ns(const struct timespec64 *ts)
 {
-	/* Prevent multiplication overflow / underflow */
-	if (ts->tv_sec >= KTIME_SEC_MAX)
+	/* Prevent multiplication overflow */
+	if ((unsigned long long)ts->tv_sec >= KTIME_SEC_MAX)
 		return KTIME_MAX;
 
-	if (ts->tv_sec <= KTIME_SEC_MIN)
-		return KTIME_MIN;
-
 	return ((s64) ts->tv_sec * NSEC_PER_SEC) + ts->tv_nsec;
 }