diff options
| author | Lukas Hannen | 2021-08-25 10:12:43 +0000 |
|---|---|---|
| committer | Thomas Gleixner | 2021-09-08 17:44:26 +0200 |
| commit | 39ff83f2f6cc5cc1458dfcea9697f96338210beb (patch) | |
| tree | 8756a234c0185493b29496080d8a682fdc8dba8d | |
| parent | 8596e589b787732c8346f0482919e83cc9362db1 (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
| -rw-r--r-- | include/linux/time64.h | 9 |
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; } |