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time: Handle negative seconds correctly in timespec64_to_ns()
commit39ff83f2f6
upstream. 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:cb47755725
("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 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 changed files with 7 additions and 2 deletions
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@ -25,7 +25,9 @@ struct itimerspec64 {
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#define TIME64_MIN (-TIME64_MAX - 1)
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#define KTIME_MAX ((s64)~((u64)1 << 63))
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#define KTIME_MIN (-KTIME_MAX - 1)
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#define KTIME_SEC_MAX (KTIME_MAX / NSEC_PER_SEC)
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#define KTIME_SEC_MIN (KTIME_MIN / NSEC_PER_SEC)
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/*
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* Limits for settimeofday():
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@ -124,10 +126,13 @@ static inline bool timespec64_valid_settod(const struct timespec64 *ts)
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*/
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static inline s64 timespec64_to_ns(const struct timespec64 *ts)
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{
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/* Prevent multiplication overflow */
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if ((unsigned long long)ts->tv_sec >= KTIME_SEC_MAX)
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/* Prevent multiplication overflow / underflow */
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if (ts->tv_sec >= KTIME_SEC_MAX)
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return KTIME_MAX;
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if (ts->tv_sec <= KTIME_SEC_MIN)
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return KTIME_MIN;
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return ((s64) ts->tv_sec * NSEC_PER_SEC) + ts->tv_nsec;
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}
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