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authorLukas Hannen <lukas.hannen@opensource.tttech-industrial.com>2021-08-25 10:12:43 +0000
committerThomas Gleixner <tglx@linutronix.de>2021-09-08 17:44:26 +0200
commit39ff83f2f6cc5cc1458dfcea9697f96338210beb (patch)
tree8756a234c0185493b29496080d8a682fdc8dba8d /include/linux/time64.h
parent8596e589b787732c8346f0482919e83cc9362db1 (diff)
time: Handle negative seconds correctly in timespec64_to_ns()
timespec64_ns() prevents multiplication overflows by comparing the seconds value of the timespec to KTIME_SEC_MAX. If the value is greater or equal it returns KTIME_MAX. But that check casts the signed seconds value to unsigned which makes the comparision true for all negative values and therefore return wrongly KTIME_MAX. Negative second values are perfectly valid and required in some places, e.g. ptp_clock_adjtime(). Remove the cast and add a check for the negative boundary which is required to prevent undefined behaviour due to multiplication underflow. Fixes: cb47755725da ("time: Prevent undefined behaviour in timespec64_to_ns()")' Signed-off-by: Lukas Hannen <lukas.hannen@opensource.tttech-industrial.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/AM6PR01MB541637BD6F336B8FFB72AF80EEC69@AM6PR01MB5416.eurprd01.prod.exchangelabs.com
Diffstat (limited to 'include/linux/time64.h')
-rw-r--r--include/linux/time64.h9
1 files changed, 7 insertions, 2 deletions
diff --git a/include/linux/time64.h b/include/linux/time64.h
index 5117cb5b5656..81b9686a2079 100644
--- a/include/linux/time64.h
+++ b/include/linux/time64.h
@@ -25,7 +25,9 @@ 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():
@@ -124,10 +126,13 @@ static inline bool timespec64_valid_settod(const struct timespec64 *ts)
*/
static inline s64 timespec64_to_ns(const struct timespec64 *ts)
{
- /* Prevent multiplication overflow */
- if ((unsigned long long)ts->tv_sec >= KTIME_SEC_MAX)
+ /* Prevent multiplication overflow / underflow */
+ if (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;
}