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Commit 12e09337 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

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: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarCarsten Emde <carsten.emde@osadl.org>
LKML-Reference: <new-submission>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: John Stultz <johnstul@us.ibm.com>
parent 54a6bc0b

include/linux/time.h

+1 −1
Original line number Diff line number Diff line
@@ -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);

kernel/time.c

+8 −1
Original line number Diff line number Diff line
@@ -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;

	}