time: Prevent 32 bit overflow with set_normalized_timespec()

set_normalized_timespec() nsec argument is of type long. The recent
timekeeping changes of ktime_get_ts() feed 

	ts->tv_nsec + tomono.tv_nsec + nsecs

to set_normalized_timespec(). On 32 bit machines that sum can be
larger than (1 << 31) and therefor result in a negative value which
screws up the result completely.

Make the nsec argument of set_normalized_timespec() s64 to fix the
problem at hand. This also prevents similar problems for future users
of set_normalized_timespec().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Carsten Emde <carsten.emde@osadl.org>
LKML-Reference: <new-submission>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: John Stultz <johnstul@us.ibm.com>

2 files changed, 9 insertions, 2 deletions

diff --git a/include/linux/time.h b/include/linux/time.h
index 256232f7e5e6..56787c093345 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -75,7 +75,7 @@ extern unsigned long mktime(const unsigned int year, const unsigned int mon,
                             const unsigned int day, const unsigned int hour,
                             const unsigned int min, const unsigned int sec);
 
-extern void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec);
+extern void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec);
 extern struct timespec timespec_add_safe(const struct timespec lhs,
                                          const struct timespec rhs);
 
diff --git a/kernel/time.c b/kernel/time.c
index 29511943871a..2e2e469a7fec 100644
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -370,13 +370,20 @@ EXPORT_SYMBOL(mktime);
  *      0 <= tv_nsec < NSEC_PER_SEC
  * For negative values only the tv_sec field is negative !
  */
-void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec)
+void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec)
 {
         while (nsec >= NSEC_PER_SEC) {
+                /*
+                 * The following asm() prevents the compiler from
+                 * optimising this loop into a modulo operation. See
+                 * also __iter_div_u64_rem() in include/linux/time.h
+                 */
+                asm("" : "+rm"(nsec));
                 nsec -= NSEC_PER_SEC;
                 ++sec;
         }
         while (nsec < 0) {
+                asm("" : "+rm"(nsec));
                 nsec += NSEC_PER_SEC;
                 --sec;
         }