time: Move ktime_t overflow checking into timespec_valid_strict

Andreas Bombe reported that the added ktime_t overflow checking added to
timespec_valid in commit 4e8b1452 ("time: Improve sanity checking of
timekeeping inputs") was causing problems with X.org because it caused
timeouts larger then KTIME_T to be invalid.

Previously, these large timeouts would be clamped to KTIME_MAX and would
never expire, which is valid.

This patch splits the ktime_t overflow checking into a new
timespec_valid_strict function, and converts the timekeeping codes
internal checking to use this more strict function.
Reported-and-tested-by: NAndreas Bombe <aeb@debian.org>
Cc: Zhouping Liu <zliu@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/linux/time.h

@@ -125,6 +125,13 @@ static inline bool timespec_valid(const struct timespec *ts)
 	/* Can't have more nanoseconds then a second */
 	if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC)
 		return false;
+	return true;
+}
+
+static inline bool timespec_valid_strict(const struct timespec *ts)
+{
+	if (!timespec_valid(ts))
+		return false;
 	/* Disallow values that could overflow ktime_t */
 	if ((unsigned long long)ts->tv_sec >= KTIME_SEC_MAX)
 		return false;

kernel/time/timekeeping.c

@@ -428,7 +428,7 @@ int do_settimeofday(const struct timespec *tv)
 	struct timespec ts_delta, xt;
 	unsigned long flags;
 
-	if (!timespec_valid(tv))
+	if (!timespec_valid_strict(tv))
 		return -EINVAL;
 
 	write_seqlock_irqsave(&tk->lock, flags);
@@ -476,7 +476,7 @@ int timekeeping_inject_offset(struct timespec *ts)
 
 	/* Make sure the proposed value is valid */
 	tmp = timespec_add(tk_xtime(tk),  *ts);
-	if (!timespec_valid(&tmp)) {
+	if (!timespec_valid_strict(&tmp)) {
 		ret = -EINVAL;
 		goto error;
 	}
@@ -659,7 +659,7 @@ void __init timekeeping_init(void)
 	struct timespec now, boot, tmp;
 
 	read_persistent_clock(&now);
-	if (!timespec_valid(&now)) {
+	if (!timespec_valid_strict(&now)) {
 		pr_warn("WARNING: Persistent clock returned invalid value!\n"
 			"         Check your CMOS/BIOS settings.\n");
 		now.tv_sec = 0;
@@ -667,7 +667,7 @@ void __init timekeeping_init(void)
 	}
 
 	read_boot_clock(&boot);
-	if (!timespec_valid(&boot)) {
+	if (!timespec_valid_strict(&boot)) {
 		pr_warn("WARNING: Boot clock returned invalid value!\n"
 			"         Check your CMOS/BIOS settings.\n");
 		boot.tv_sec = 0;
@@ -713,7 +713,7 @@ static struct timespec timekeeping_suspend_time;
 static void __timekeeping_inject_sleeptime(struct timekeeper *tk,
 							struct timespec *delta)
 {
-	if (!timespec_valid(delta)) {
+	if (!timespec_valid_strict(delta)) {
 		printk(KERN_WARNING "__timekeeping_inject_sleeptime: Invalid "
 					"sleep delta value!\n");
 		return;