[LU-18069] Incorrect timespec64_to_ns() in sles15sp5 kernel

• Type: Bug
• Resolution: Unresolved
• Priority: Minor
• Severity: 3
• Assignee: WC Triage
• Reporter: Feng Lei

Description

This bug causes sanity/39m fails in LU-1158, which tries to support nanosecond timestamps.

Wrong version of timespec64_to_ns() function in sles15sp5 (in time64.h):

#define KTIME_MAX                       ((s64)~((u64)1 << 63))
#define KTIME_SEC_MAX                   (KTIME_MAX / NSEC_PER_SEC)

static inline s64 timespec64_to_ns(const struct timespec64 *ts)
{
        /* Prevent multiplication overflow */
        if ((unsigned long long)ts->tv_sec >= KTIME_SEC_MAX)
                return KTIME_MAX;
        return ((s64) ts->tv_sec * NSEC_PER_SEC) + ts->tv_nsec;
}

If tv_sec is a negative value, it always returns KTIME_MAX. Then sanity/test_39m fails.

Correct version of timespec64_to_ns() in rocky 8.9:

#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)

static inline s64 timespec64_to_ns(const struct timespec64 *ts)
{
        /* 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;
}

This version can handle negative tv_sec correctly.

Issue Links

• is related to: LU-1158 nanosecond timestamp support for Lustre