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);
We just suppress signed integer-overflow warning implicitly by casting (and get an unsigned integer-overflow warning instead — try `luajit -e "os.time({ day = 0, month = 0, year = 0 })"` with clang and -fsanitize=integer).
 
The ignored warning is meaningful in a case, when we get a valid input for mktime() and it returns a valid output for it args, but that result is invalid for args of os.time() due to integer overflow.
 
I think, the range checks for Lua os.time() args are needed to provide predictable error response. At least, a check for year arg to prevent the invalid result of os.time().
 
Where are some example calls below (Ubuntu 24, amd64) with some debug printing.
 
Not patched version — warning + invalid result
/src/src/luajit -e "print(os.time({ day = 1, month = 1, year = -2^31 }),'\n')"
lib_os.c:244:42: runtime error: signed integer overflow: -2147483648 - 1900 cannot be represented in type 'int'
lj_cf_os_time: (1) <- ts.tm_mday=1 ts.tm_mon=0 ts.tm_year=2147481748
lj_cf_os_time: (2) -> ts.tm_mday=1 ts.tm_mon=0 ts.tm_year=2147481748 t=67767976233576000 errno=0
6.7767976233576e+16
 
Patched version — invalid result only
/src/src/luajit -e "print(os.time({ day = 1, month = 1, year = -2^31 }),'\n')"
lj_cf_os_time: (1) <- getfield(month)=1 getfield(year)=-2147483648 (u)getfield(month)=0 (u)getfield(year)=2147481748 ts.tm_mday=1 ts.tm_mon=0 ts.tm_year=2147481748
lj_cf_os_time: (2) -> ts.tm_mday=1 ts.tm_mon=0 ts.tm_year=2147481748 t=67767976233576000 errno=0
6.7767976233576e+16
 
Some more calls for example: the mktime() may ignore invalid tm_mday, tm_mon values of struct tm and update them in a «no error» case.
 
Not patched version
 
/src/src/luajit -e "print(os.time({ day = -2^31, month = -2^31, year = -2^31+1900 }),'\n')"
lib_os.c:243:42: runtime error: signed integer overflow: -2147483648 - 1 cannot be represented in type 'int'
lj_cf_os_time: (1) ts.tm_mday=-2147483648 ts.tm_mon=2147483647 ts.tm_year=-2147483648
lj_cf_os_time: (2) ts.tm_mday=20 ts.tm_mon=0 ts.tm_year=-1974406288 t=-62306246666232000 errno=0
-6.2306246666232e+16
 
/src/src/luajit -e "print(os.time({ day = -2^31, month = -2^31, year = -2^31+1899 }),'\n')"
lib_os.c:243:42: runtime error: signed integer overflow: -2147483648 - 1 cannot be represented in type 'int'
lib_os.c:244:42: runtime error: signed integer overflow: -2147481749 - 1900 cannot be represented in type 'int'
lj_cf_os_time: (1) ts.tm_mday=-2147483648 ts.tm_mon=2147483647 ts.tm_year=2147483647
lj_cf_os_time: (2) ts.tm_mday=-2147483648 ts.tm_mon=2147483647 ts.tm_year=2147483647 t=-1 errno=75
nil
 
Patched version
 
/src/src/luajit -e "print(os.time({ day = -2^31, month = -2^31, year = -2^31+1900 }),'\n')"
lj_cf_os_time: (1) <- getfield(month)=-2147483648 getfield(year)=-2147481748 (u)getfield(month)=2147483647 (u)getfield(year)=2147483648 ts.tm_mday=-2147483648 ts.tm_mon=2147483647 ts.tm_year=-2147483648
lj_cf_os_time: (2) -> ts.tm_mday=20 ts.tm_mon=0 ts.tm_year=-1974406288 t=-62306246666232000 errno=0
-6.2306246666232e+16
 
/src/src/luajit -e "print(os.time({ day = -2^31, month = -2^31, year = -2^31+1899 }),'\n')"
lj_cf_os_time: (1) <- getfield(month)=-2147483648 getfield(year)=-2147481749 (u)getfield(month)=2147483647 (u)getfield(year)=2147483647 ts.tm_mday=-2147483648 ts.tm_mon=2147483647 ts.tm_year=2147483647
lj_cf_os_time: (2) -> ts.tm_mday=-2147483648 ts.tm_mon=2147483647 ts.tm_year=2147483647 t=-1 errno=75
nil
 
ts.tm_isdst = getboolfield(L, "isdst");
t = mktime(&ts);
}
diff --git a/test/tarantool-tests/lj-1454-os-time.test.lua b/test/tarantool-tests/lj-1454-os-time.test.lua
new file mode 100644
index 00000000..2a48750c
--- /dev/null
+++ b/test/tarantool-tests/lj-1454-os-time.test.lua
@@ -0,0 +1,19 @@
+local tap = require('tap')
+
+-- The test file to demonstrate UBSan warning for `os.time()` with
+-- a huge indices value for month and/or year.
+-- See also: https://github.com/LuaJIT/LuaJIT/issues/1454.
+local test = tap.test('lj-1454-os-time')
+
+test:plan(1)
+
+local INT_MIN = -2 ^ 31
+
+local cur_time = os.time({
+ day = 1,
+ month = INT_MIN,
+ year = INT_MIN,
+})
+test:is(cur_time, nil, 'os.time() with INT_MIN')
+
+test:done(true)
--
2.43.0