RFR: 8360664: Null pointer dereference in src/hotspot/share/prims/jvmtiTagMap.cpp in IterateOverHeapObjectClosure::do_object()

[Artem Semenov]

The defect has been detected and confirmed in the function ```IterateOverHeapObjectClosure::do_object()``` located in the file ```src/hotspot/share/prims/jvmtiTagMap.cpp``` with static code analysis. This defect can potentially lead to a null pointer dereference.

The pointer ```oop o``` is passed to the constructor of the CallbackWrapper class, where it is dereferenced without a null check.


Found by Linux Verification Center (linuxtesting.org) with SVACE. signed-off-by: Artem Semenov (savoptik at altlinux.org).

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Commit messages:
 - 8360664 Null pointer dereference in src/hotspot/share/prims/jvmtiTagMap.cpp in IterateOverHeapObjectClosure::do_object()

Changes: https://git.openjdk.org/jdk/pull/26002/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26002&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8360664
  Stats: 4 lines in 1 file changed: 2 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/26002.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26002/head:pull/26002

PR: https://git.openjdk.org/jdk/pull/26002