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

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

[Sergey Bronnikov via Tarantool-patches]

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

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

[Sergey Kaplun via Tarantool-patches]

Hi, Sergey!
Thanks for the patch!
LGTM, with minor ignorable comments below.

On 05.06.26, Sergey Bronnikov wrote:
> 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

Typo: s/to returned/to be returned/

> `get_field()`.

I am suggesting rephrasing this paragraph a bit to make it more clear:

| The function `lj_cf_os_time()` calculates the `tm_mon` and `tm_year`
| values using `get_field()`. If this helper function returns a negative
| result, subtraction may lead to undefined behavior due to signed integer
| overflow. The patch fixes the issue by adding a cast to the value
| returned by `get_field()`.

Feel free to ignore.

> 
> 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

<snipped>

> 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

I prefer the <lj-1454-ub-os-time.test.lua> name (as you named the
branch). Feel free to ignore.

> @@ -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.

s/a huge indices value/huge negative index values/

> +-- See also: https://github.com/LuaJIT/LuaJIT/issues/1454.
> +local test = tap.test('lj-1454-os-time')

I prefer the lj-1454-ub-os-time name (as you named the branch). Feel
free to ignore.

> +
> +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
> 

-- 
Best regards,
Sergey Kaplun

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

[Sergey Bronnikov via Tarantool-patches]

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Hi, Sergey,

thanks for the review! See my comments below.

Sergey

On 6/6/26 10:14, Sergey Kaplun via Tarantool-patches wrote:
> Hi, Sergey!
> Thanks for the patch!
> LGTM, with minor ignorable comments below.
>
> On 05.06.26, Sergey Bronnikov wrote:
>> 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
> Typo: s/to returned/to be returned/
Fixed.
>
>> `get_field()`.
> I am suggesting rephrasing this paragraph a bit to make it more clear:
>
> | The function `lj_cf_os_time()` calculates the `tm_mon` and `tm_year`
> | values using `get_field()`. If this helper function returns a negative
> | result, subtraction may lead to undefined behavior due to signed integer
> | overflow. The patch fixes the issue by adding a cast to the value
> | returned by `get_field()`.
>
> Feel free to ignore.
Updated.
>
>> 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
> <snipped>
>
>> 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
> I prefer the <lj-1454-ub-os-time.test.lua> name (as you named the
> branch). Feel free to ignore.

Updated:

$ git show --name-only

<snipped>
src/lib_os.c
test/tarantool-tests/lj-1454-ub-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.
> s/a huge indices value/huge negative index values/

Updated:

--- a/test/tarantool-tests/lj-1454-ub-os-time.test.lua
+++ b/test/tarantool-tests/lj-1454-ub-os-time.test.lua
@@ -1,7 +1,7 @@
  local tap = require('tap')

  -- The test file to demonstrate UBSan warning for `os.time()` with
--- a huge indices value for month and/or year.
+-- huge negative index values for month and/or year.
  -- See also: https://github.com/LuaJIT/LuaJIT/issues/1454.
  local test = tap.test('lj-1454-os-time')


>
>> +-- See also:https://github.com/LuaJIT/LuaJIT/issues/1454.
>> +local test = tap.test('lj-1454-os-time')
> I prefer the lj-1454-ub-os-time name (as you named the branch). Feel
> free to ignore.

Updated:

  -- See also: https://github.com/LuaJIT/LuaJIT/issues/1454.
-local test = tap.test('lj-1454-os-time')
+local test = tap.test('lj-1454-ub-os-time')

test:plan(1)

>
>> +
>> +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
>>

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

[Sergey Kaplun via Tarantool-patches]

Sergey,
Thanks for the fixes!
LGTM!

-- 
Best regards,
Sergey Kaplun

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

[Evgeniy Temirgaleev via Tarantool-patches]

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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
>

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

[Evgeniy Temirgaleev via Tarantool-patches]

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Hi, Sergey!

It’s an addition for my previous letter. I am sorry, but the some part of the quote was missed in it.

My single comment is about these lines:

> - 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);

<please, see the comment text in the first letter>

--
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);
> 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
>

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