RFR: 8332818: ubsan: archiveHeapLoader.cpp:70:27: runtime error: applying non-zero offset 18446744073707454464 to null pointer

[Matthias Baesken]

On Wed, 12 Jun 2024 03:09:55 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> When running :tier1 hs tests, the following issue has been reported when running with ubsan enabled binaries (configure flag --enable-ubsan)  
>> 
>>  stderr: [/jdk/src/hotspot/share/cds/archiveHeapLoader.cpp:70:27: runtime error: applying non-zero offset 18446744073707454464 to null pointer
>>     #0 0x7f33db52823f in ArchiveHeapLoader::init_mapped_heap_info(unsigned char*, long, int) /jdk/src/hotspot/share/cds/archiveHeapLoader.cpp:70
>>     #1 0x7f33dc6d3ad4 in FileMapInfo::map_heap_region_impl() /jdk/src/hotspot/share/cds/filemap.cpp:2211
>>     #2 0x7f33dc6d4ba4 in FileMapInfo::map_heap_region() /jdk/src/hotspot/share/cds/filemap.cpp:2129
>>     #3 0x7f33dc6d52a7 in FileMapInfo::map_or_load_heap_region() /jdk/src/hotspot/share/cds/filemap.cpp:2019
>>     #4 0x7f33ddaf7fdb in MetaspaceShared::map_archives(FileMapInfo*, FileMapInfo*, bool) /jdk/src/hotspot/share/cds/metaspaceShared.cpp:1183
>>     #5 0x7f33ddaf8f54 in MetaspaceShared::initialize_runtime_shared_and_meta_spaces() /jdk/src/hotspot/share/cds/metaspaceShared.cpp:943
>>     #6 0x7f33ddadd60f in Metaspace::global_initialize() /jdk/src/hotspot/share/memory/metaspace.cpp:714
>>     #7 0x7f33de9bc7f9 in universe_init() /jdk/src/hotspot/share/memory/universe.cpp:866
>>     #8 0x7f33dcc93691 in init_globals() /jdk/src/hotspot/share/runtime/init.cpp:128
>>     #9 0x7f33de92a720 in Threads::create_vm(JavaVMInitArgs*, bool*) /jdk/src/hotspot/share/runtime/threads.cpp:553
>>     #10 0x7f33dd02d477 in JNI_CreateJavaVM_inner /jdk/src/hotspot/share/prims/jni.cpp:3581
>>     #11 0x7f33dd02d477 in JNI_CreateJavaVM /jdk/src/hotspot/share/prims/jni.cpp:3672
>>     #12 0x7f33e42a90e5 in InitializeJVM /jdk/src/java.base/share/native/libjli/java.c:1550
>>     #13 0x7f33e42a90e5 in JavaMain /jdk/src/java.base/share/native/libjli/java.c:491
>>     #14 0x7f33e42b2748 in ThreadJavaMain /jdk/src/java.base/unix/native/libjli/java_md.c:642
>>     #15 0x7f33e42616e9 in start_thread (/lib64/libpthread.so.0+0xa6e9) (BuildId: 2f8d3c2d0f4d7888c2598d2ff6356537f5708a73)
>>     #16 0x7f33e391550e in clone (/lib64/libc.so.6+0x11850e) (BuildId: f732026552f6adff988b338e92d466bc81a01c37)
>> 
>> 
>> Seems that  `CompressedOops::base() ` can be nullptr , so adding to it some non-zero value triggers ubsan because of undefined behavior.  In the JBS-bug there was already a little discussion and it seems disabling this warning might be an option.
>> 
>> otherwise some workaround like
>> 
>> template<typename T>
>> T* add_to_ptr_maybe_null(T* ptr, uintptr_t val)...
>
> src/hotspot/share/cds/archiveHeapLoader.cpp line 64:
> 
>> 62: // Every mapped region is offset by _mapped_heap_delta from its requested address.
>> 63: // See FileMapInfo::heap_region_requested_address().
>> 64: // avoid adding to CompressedOops::base() == nullptr
> 
> I don't understand what the comment is trying to say.
> 
> This is surely a bug in ubsan as I should be able to take any address, including zero, and  add an offset to get another address!

Hi David, it is no ubsan-bug, see also here for more details about this warning  https://reviews.llvm.org/D67122 .

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

PR Review Comment: https://git.openjdk.org/jdk/pull/19597#discussion_r1635899579