[Tarantool-patches] [PATCH luajit] Prevent sanitizer warning in os.time().

[Sergey Bronnikov via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

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);
     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