Hi, Sergey! Thanks for the patch!

Please, see my comment.

--
Best regards,

Evgeniy Temirgaleev

From: Sergey Bronnikov <estetus@gmail.com>
To: tarantool-patches@dev.tarantool.org, Sergey Kaplun <skaplun@tarantool.org>,e.temirgaleev@tarantool.org
Date: Friday, June 5, 2026 6:19 PM +03:00

From: Mike Pall <mike>

Reported by Sergey Bronnikov.

(cherry picked from commit 86d414f5cae062b06998ec66b0696a47d4f6a0f0)

The function `lj_cf_os_time()` calculates `tm_mon` and `tm_year`
values using `get_field()` and when the helper function returns
a negative value the resulted values may be negative as well. This
is an undefined behaviour (signed integer overflow). The patch fixes
that by adding a cast for the resulted value to returned by
`get_field()`.

Sergey Bronnikov:
* added the description and the test for the problem

Part of tarantool/tarantool#12480
---

Branch: https://github.com/tarantool/luajit/tree/ligurio/lj-1454-ub-os-time

Related issues:

* https://github.com/tarantool/tarantool/issues/12480
* https://github.com/LuaJIT/LuaJIT/issues/1454

src/lib_os.c | 4 ++--
test/tarantool-tests/lj-1454-os-time.test.lua | 19 +++++++++++++++++++
2 files changed, 21 insertions(+), 2 deletions(-)
create mode 100644 test/tarantool-tests/lj-1454-os-time.test.lua

diff --git a/src/lib_os.c b/src/lib_os.c
index ffbc3fdc..0feb0d47 100644
--- a/src/lib_os.c
+++ b/src/lib_os.c
@@ -239,8 +239,8 @@ LJLIB_CF(os_time)
ts.tm_min = getfield(L, "min", 0);
ts.tm_hour = getfield(L, "hour", 12);
ts.tm_mday = getfield(L, "day", -1);
- ts.tm_mon = getfield(L, "month", -1) - 1;
- ts.tm_year = getfield(L, "year", -1) - 1900;
+ ts.tm_mon = (int)((unsigned int)getfield(L, "month", -1) - 1u);
+ ts.tm_year = (int)((unsigned int)getfield(L, "year", -1) - 1900u);