[Tarantool-patches] [PATCH luajit] Limit number of string format elements to compile.
Sergey Bronnikov
sergeyb at tarantool.org
Thu Sep 5 19:24:07 MSK 2024
Hi, Sergey!
Thanks for the fixes! LGTM
see my comments below
On 04.09.2024 18:02, Sergey Kaplun wrote:
> Hi, Sergey!
> Thanks for the review!
> See my answers below.
>
> On 04.09.24, Sergey Bronnikov wrote:
>> Hi, Sergey,
>>
>> thanks for the patch!
>>
>> See my comments below.
>>
>> Sergey
>>
>> On 26.08.2024 13:25, Sergey Kaplun wrote:
>>> From: Mike Pall <mike>
>>>
>>> Reported by pwnhacker0x18.
>>>
>>> (cherry picked from commit 4fc48c50fe3f3f5a9680bada5c0c0d0d7eb345a3)
>>>
>>> When compiling `string.format()` with a huge sequence of elements, it is
>>> possible that too many KGC IRs underflow the IR buffer. This patch
>>> limits the maximum number of `string.format()` elements to be compiled
>>> to 100.
>>>
>>> Sergey Kaplun:
>>> * added the description and the test for the problem
>>>
>>> Part of tarantool/tarantool#10199
>>> ---
>>>
>>> Branch:https://github.com/tarantool/luajit/tree/skaplun/lj-1203-limit-format-elements
>>> Related issues:
>>> *https://github.com/tarantool/tarantool/issues/10199
>>> *https://github.com/LuaJIT/LuaJIT/issues/1203
>>>
>>> src/lj_ffrecord.c | 2 ++
>>> .../lj-1203-limit-format-elements.test.lua | 28 +++++++++++++++++++
>>> 2 files changed, 30 insertions(+)
>>> create mode 100644 test/tarantool-tests/lj-1203-limit-format-elements.test.lua
>>>
>>> diff --git a/src/lj_ffrecord.c b/src/lj_ffrecord.c
>>> index d5fc081e..3b82d044 100644
>>> --- a/src/lj_ffrecord.c
>>> +++ b/src/lj_ffrecord.c
>>> @@ -962,6 +962,7 @@ static void LJ_FASTCALL recff_string_format(jit_State *J, RecordFFData *rd)
>>> TRef hdr, tr;
>>> FormatState fs;
>>> SFormat sf;
>>> + int nfmt = 0;
>>> /* Specialize to the format string. */
>>> emitir(IRTG(IR_EQ, IRT_STR), trfmt, lj_ir_kstr(J, fmt));
>>> tr = hdr = recff_bufhdr(J);
>>> @@ -1031,6 +1032,7 @@ static void LJ_FASTCALL recff_string_format(jit_State *J, RecordFFData *rd)
>>> recff_nyiu(J, rd);
>>> return;
>>> }
>>> + if (++nfmt > 100) lj_trace_err(J, LJ_TRERR_TRACEOV);
>>> }
>>> J->base[0] = emitir(IRT(IR_BUFSTR, IRT_STR), tr, hdr);
>>> }
>>> diff --git a/test/tarantool-tests/lj-1203-limit-format-elements.test.lua b/test/tarantool-tests/lj-1203-limit-format-elements.test.lua
>>> new file mode 100644
>>> index 00000000..f17d4e37
>>> --- /dev/null
>>> +++ b/test/tarantool-tests/lj-1203-limit-format-elements.test.lua
>>> @@ -0,0 +1,28 @@
>>> +local tap = require('tap')
>>> +
>>> +-- Test file to demonstrate LuaJIT incorrect recording of
>>> +-- `string.format()` function with huge amount of elements.
>>> +-- See also:https://github.com/LuaJIT/LuaJIT/issues/1173.
>> Seems a correct link ishttps://github.com/LuaJIT/LuaJIT/issues/1203
> Fixed, thanks!
> Branch is force-pushed.
>
> ===================================================================
> diff --git a/test/tarantool-tests/lj-1203-limit-format-elements.test.lua b/test/tarantool-tests/lj-1203-limit-format-elements.test.lua
> index f17d4e37..bf250000 100644
> --- a/test/tarantool-tests/lj-1203-limit-format-elements.test.lua
> +++ b/test/tarantool-tests/lj-1203-limit-format-elements.test.lua
> @@ -2,7 +2,7 @@ local tap = require('tap')
>
> -- Test file to demonstrate LuaJIT incorrect recording of
> -- `string.format()` function with huge amount of elements.
> --- See also:https://github.com/LuaJIT/LuaJIT/issues/1173.
> +-- See also:https://github.com/LuaJIT/LuaJIT/issues/1203.
>
> local test = tap.test('lj-1203-limit-format-elements'):skipcond({
> ['Test requires JIT enabled'] = not jit.status(),
> ===================================================================
Thanks!
>>> +
>>> +local test = tap.test('lj-1203-limit-format-elements'):skipcond({
>>> + ['Test requires JIT enabled'] = not jit.status(),
>>> +})
>>> +
>>> +test:plan(2)
>>> +
>>> +jit.opt.start('hotloop=1')
>>> +
>>> +-- XXX: Use a huge amount of format elements to process, which
>>> +-- creates a lot of string constants.
>>> +local NELEMENTS = 25000
>> Why 25000? It is reproduced with 10000 as well.
> It is flaky-reproducible with less amount inside our test suite (at
> least on my laptop), so I prefer to keep this number of elements.
>
Okay
>>
>>> +local fmt = ('%'):rep(NELEMENTS * 2)
>>> +local expected = ('%'):rep(NELEMENTS)
>>> +local result
>>> +for _ = 1, 4 do
>>> + result = fmt:format()
>>> +end
>>> +
>>> +test:ok(true, 'no IR buffer underflow')
>> Why do you need this check? Why the following check it not enough?
> We usually check both (no assertion and correctness) where it is easily
> done.
Looks like the first one is excessive and I would remove it.
But I'll not insist.
>
>>> +test:is(result, expected, 'correct result')
>>> +
>>> +test:done(true)
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