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authorThomas Gleixner <tglx@linutronix.de>2009-09-14 23:37:40 +0200
committerThomas Gleixner <tglx@linutronix.de>2009-09-15 10:17:30 +0200
commit12e09337fe238981cb0c87543306e23775d1a143 (patch)
tree4c5052a801e6868ce2c701af10bf55f5ec5a4929
parent54a6bc0b071c50150bc6d1da16c2cd9a963e288c (diff)
downloadlinux-12e09337fe238981cb0c87543306e23775d1a143.tar.bz2
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>
-rw-r--r--include/linux/time.h2
-rw-r--r--kernel/time.c9
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;
}