8332955: ubsan: runningCounters.cpp:48:61: runtime error: member call on null pointer of type 'struct VirtualSpaceList'

[MBaesken]

When running jtreg HS :tier1 tests (with ubsan enabled binaries) this error can be seen on Linux ppc64.
Probably we should add a NULL check because calling into a nullptr is probably not a good idea (although no crash is observed).

runtime/os/TestHugePageDecisionsAtVMStartup_THP_enabled.jtr

/jdk/src/hotspot/share/memory/metaspace/runningCounters.cpp:48:61: runtime error: member call on null pointer of type 'struct VirtualSpaceList'
#0 0x7fffabe667c8 in metaspace::RunningCounters::reserved_words_nonclass() (/images/jdk/lib/server/libjvm.so+0x78667c8)
#1 0x7fffab6a25c0 in MetaspaceUtils::get_statistics(Metaspace::MetadataType) (/images/jdk/lib/server/libjvm.so+0x70a25c0)
#2 0x7fffab6a2708 in MetaspaceUtils::get_combined_statistics() (/images/jdk/lib/server/libjvm.so+0x70a2708)
#3 0x7fffab5ce630 in MemBaseline::baseline(bool) (/images/jdk/lib/server/libjvm.so+0x6fce630)
#4 0x7fffab61bf10 in MemTracker::report(bool, outputStream*, unsigned long) (/images/jdk/lib/server/libjvm.so+0x701bf10)
#5 0x7fffab61cb84 in MemTracker::error_report(outputStream*) (/images/jdk/lib/server/libjvm.so+0x701cb84)
#6 0x7fffac93f1e8 in VMError::report(outputStream*, bool) (/images/jdk/lib/server/libjvm.so+0x833f1e8)
#7 0x7fffac944630 in VMError::report_and_die(int, char const*, char const*, char*, Thread*, unsigned char*, void*, void*, char const*, int, unsigned long) (/images/jdk/lib/server/libjvm.so+0x8344630)
#8 0x7fffa9d69ffc in report_fatal(VMErrorType, char const*, int, char const*, ...) (/images/jdk/lib/server/libjvm.so+0x5769ffc)
#9 0x7fffaadff93c in TypedFlagAccessImpl<unsigned int, EventUnsignedIntFlagChanged>::check_constraint_and_set(JVMFlag*, void*, JVMFlagOrigin, bool) const [clone .part.0] (/images/jdk/lib/server/libjvm.so+0x67ff93c)
#10 0x7fffaae12bb8 in RangedFlagAccessImpl<unsigned long, EventUnsignedLongFlagChanged>::set_impl(JVMFlag*, void*, JVMFlagOrigin) const (/images/jdk/lib/server/libjvm.so+0x6812bb8)
#11 0x7fffaae04b8c in JVMFlagAccess::set_or_assert(JVMFlagsEnum, int, void*, JVMFlagOrigin) (/images/jdk/lib/server/libjvm.so+0x6804b8c)
#12 0x7fffa9a79fa8 in CodeCache::initialize_heaps() (/images/jdk/lib/server/libjvm.so+0x5479fa8)
#13 0x7fffa9a7ac10 in CodeCache::initialize() (/images/jdk/lib/server/libjvm.so+0x547ac10)
#14 0x7fffaa81af08 in init_globals() (/images/jdk/lib/server/libjvm.so+0x621af08)
#15 0x7fffac68baa8 in Threads::create_vm(JavaVMInitArgs*, bool*) (/images/jdk/lib/server/libjvm.so+0x808baa8)
#16 0x7fffaaca20b4 in JNI_CreateJavaVM (/images/jdk/lib/server/libjvm.so+0x66a20b4)
#17 0x7fffb17b3068 in InitializeJVM /jdk/src/java.base/share/native/libjli/java.c:1550
#18 0x7fffb17b3068 in JavaMain /jdk/src/java.base/share/native/libjli/java.c:491
#19 0x7fffb17bef1c in ThreadJavaMain /jdk/src/java.base/unix/native/libjli/java_md.c:642
#20 0x7fffb16d9714 in start_thread (/lib64/libpthread.so.0+0x9714)
#21 0x7fffb0a8b774 in __GI___clone (/lib64/libc.so.6+0x13b774)

---

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Issue

• JDK-8332955: ubsan: runningCounters.cpp:48:61: runtime error: member call on null pointer of type 'struct VirtualSpaceList' (Bug - P4) ⚠️ Issue is not open.

Reviewers

• Martin Doerr (@TheRealMDoerr - Reviewer)

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• 00: Full (a1c0e13b)

[TheRealMDoerr]

I'm not very familiar with this code, but if reserved_words_nonclass() happens to be called before the VirtualSpaceList is initialized, I think this fix is good. Should be reviewed by a metaspace expert.
/reviewers 2

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@TheRealMDoerr
The total number of required reviews for this PR (including the jcheck configuration and the last /reviewers command) is now set to 2 (with at least 1 Reviewer, 1 Author).

[MBaesken]

I'm not very familiar with this code, but if reserved_words_nonclass() happens to be called before the VirtualSpaceList is initialized, I think this fix is good.

Thanks for the review !
I don't think that ubsan is 'lying' to us here, so far at least the findings were all correct. From the backtrace above you can see that this happens rather early in the JVM lifetime, this might be the reason why we run into a nullptr.

[dholmes-ora]

Given this problem was discovered when following a crash path during VM init, it makes me wonder what other code in this class we may try to use during error reporting that may not yet be initialized?

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