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mruby-time: normalize microseconds before converting to nanoseconds

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when converting microseconds to nanoseconds, multiplying very large
usec values by 1000 can cause signed integer overflow. for example,
Time.at(0, 9999999999990768) would trigger ASAN runtime error.

fixed by normalizing microseconds >= 1000000 (or <= -1000000) to
seconds before the multiplication, preventing overflow while maintaining
correct time representation. this normalization converts excess
microseconds to seconds, leaving only the fractional part for
multiplication.

applied fix to both time_alloc() and mrb_time_at() functions.

Co-authored-by: Claude <noreply@anthropic.com>
This commit is contained in:
Yukihiro "Matz" Matsumoto
2025-11-24 08:06:40 +09:00
parent 78f9b5c52f
commit 857de45036
1 changed files with 21 additions and 2 deletions
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mrbgems/mruby-time/src/time.c
+21 -2
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@@ -485,11 +485,20 @@ static struct mrb_time*
time_alloc(mrb_state *mrb, mrb_value sec, mrb_value usec, enum mrb_timezone timezone)
{
time_t tsec, tusec; /* Variables to hold converted seconds and microseconds */
time_t nsec;
tsec = mrb_to_time_t(mrb, sec, &tusec);
tusec += mrb_to_time_t(mrb, usec, NULL);
return time_alloc_time(mrb, tsec, tusec * NSECS_PER_USEC, timezone);
/* Normalize microseconds to avoid overflow when converting to nanoseconds */
if (tusec >= USECS_PER_SEC || tusec <= -USECS_PER_SEC) {
time_t sec_adjustment = tusec / USECS_PER_SEC;
tusec -= sec_adjustment * USECS_PER_SEC;
tsec += sec_adjustment;
}
nsec = tusec * NSECS_PER_USEC;
return time_alloc_time(mrb, tsec, nsec, timezone);
}
/*
@@ -596,7 +605,17 @@ time_now(mrb_state *mrb, mrb_value self)
MRB_API mrb_value
mrb_time_at(mrb_state *mrb, time_t sec, time_t usec, enum mrb_timezone zone)
{
return time_make_time(mrb, mrb_class_get_id(mrb, MRB_SYM(Time)), sec, usec * NSECS_PER_USEC, zone);
time_t nsec;
/* Normalize microseconds to avoid overflow when converting to nanoseconds */
if (usec >= USECS_PER_SEC || usec <= -USECS_PER_SEC) {
time_t sec_adjustment = usec / USECS_PER_SEC;
usec -= sec_adjustment * USECS_PER_SEC;
sec += sec_adjustment;
}
nsec = usec * NSECS_PER_USEC;
return time_make_time(mrb, mrb_class_get_id(mrb, MRB_SYM(Time)), sec, nsec, zone);
}
/*