RFR: 8360941: [ubsan] MemRegion::end() shows runtime error: applying non-zero offset 8388608 to null pointer [v7]

[Thomas Stuefe]

On Tue, 22 Jul 2025 07:49:41 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

>> When running HS test
>> gtest/GTestWrapper.java
>> with ubsan-enabled binaries on macOS aarch64, the following error is reported (did not see this so far on Linux but there we use gcc and it seems the gcc/ubsan checks are a bit more limited).
>> 
>> test/hotspot/gtest/gc/g1/test_freeRegionList.cpp:37: Failure
>> Death test: child_G1FreeRegionList_length_()
>>     Result: died but not with expected exit code:
>>             Terminated by signal 6 (core dumped)
>> Actual msg:
>> 
>> [  DEATH   ] /jdk/src/hotspot/share/memory/memRegion.hpp:66:43: runtime error: applying non-zero offset 8388608 to null pointer
>> [  DEATH   ]     #0 0x108afd6f4 in MemRegion::end() const+0x84 (libjvm.dylib:arm64+0x16556f4)
>> [  DEATH   ]     #1 0x1075c68a0 in G1FreeRegionList_length_other_vm_Test::TestBody()+0x380 (libjvm.dylib:arm64+0x11e8a0)
>> [  DEATH   ]     #2 0x1090f3bb0 in testing::Test::Run()+0xc0 (libjvm.dylib:arm64+0x1c4bbb0)
>> [  DEATH   ]     #3 0x1090f4d94 in testing::TestInfo::Run()+0x1e4 (libjvm.dylib:arm64+0x1c4cd94)
>> [  DEATH   ]     #4 0x1090f6754 in testing::TestSuite::Run()+0x43c (libjvm.dylib:arm64+0x1c4e754)
>> [  DEATH   ]     #5 0x109103ca0 in testing::internal::UnitTestImpl::RunAllTests()+0x48c (libjvm.dylib:arm64+0x1c5bca0)
>> [  DEATH   ]     #6 0x109103588 in testing::UnitTest::Run()+0x78 (libjvm.dylib:arm64+0x1c5b588)
>> [  DEATH   ]     #7 0x1074a9ac0 in runUnitTestsInner(int, char**)+0x724 (libjvm.dylib:arm64+0x1ac0)
>> [  DEATH   ]     #8 0x102dc3f18 in main+0x2c (gtestLauncher:arm64+0x100003f18)
>> [  DEATH   ]     #9 0x196fea0dc  (<unknown module>)
>> [  DEATH   ] 
>> [  DEATH   ] SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /jdk/src/hotspot/share/memory/memRegion.hpp:66:43 in 
>> [  DEATH   ] 
>> 
>> 
>> 
>> Seems the test_freeRegionList.cpp uses a special MemRegion starting at nullptr ; but this causes a bit of trouble when adding to start == nullptr .
>> So far I see this issue just in the gtest, seems other MemRegion objects do not start at nullptr .
>
> Matthias Baesken has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Alignment

Changes requested by stuefe (Reviewer).

test/hotspot/gtest/gc/g1/test_freeRegionList.cpp line 50:

> 48:   const size_t sz = szw * BytesPerWord;
> 49:   const size_t lpsz = os::large_page_size();
> 50:   char* addr = os::reserve_memory_aligned(sz, lpsz, mtTest);

Suggestion:

  char* addr = os::reserve_memory_aligned(sz, G1HeapRegion::GrainBytes, mtTest);


@MBaesken you want to align the start address at region size; not sure the G1 code we call in this test cares, but it might.

test/hotspot/gtest/gc/g1/test_freeRegionList.cpp line 94:

> 92:   bot_storage->uncommit_regions(0, num_regions_in_test);
> 93:   delete bot_storage;
> 94:   os::release_memory(addr, szw);

Wrong size; release_memory takes bytes, not words. Use `sz`.

This explains also the crash on Windows you told me about in your mail. Was this patch also in the testing queue?

-------------

PR Review: https://git.openjdk.org/jdk/pull/26216#pullrequestreview-3042623856
PR Review Comment: https://git.openjdk.org/jdk/pull/26216#discussion_r2222289653
PR Review Comment: https://git.openjdk.org/jdk/pull/26216#discussion_r2222273575