jmm_GetDiagnosticCommandArgumentsInfo and jmm_GetDiagnosticCommandInfo are used
to query the hotspot about diagnostic commands. They provide output arrays for
the information:
void jmm_GetDiagnosticCommandArgumentsInfo(JNIEnv *env,
jstring command, dcmdArgInfo* infoArray)
but array size is implicitly assumed to be known to both caller and callee.
Caller and callee negotiate those sizes in prior steps, but things can go
wrong. E.g. I recently hunted a bug where `DCmd::number_arguments()` was off -
did not reflect the real number of its jcmd parameters - which led to a hidden
memory overwriter.
Thankfully, JDK-8264565 rewrote the dcmd framework to deal with this particular
issue (The VM I analyzed was older). Still, it would be good if we had
additional safety measures here.
-------------
Testing:
- manual tests with artificially induced error in one dcmd for debug, release
- GHAs (which include tier1 serviceability jcmd tests which use JMX and
exercise these APIs)
-------------
Commit messages:
- explicitly pass output array size and check it in hotspot
Changes: https://git.openjdk.java.net/jdk/pull/6363/files
Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6363&range=00
Issue: https://bugs.openjdk.java.net/browse/JDK-8277029
Stats: 18 lines in 3 files changed: 8 ins; 0 del; 10 mod
Patch: https://git.openjdk.java.net/jdk/pull/6363.diff
Fetch: git fetch https://git.openjdk.java.net/jdk pull/6363/head:pull/6363
PR: https://git.openjdk.java.net/jdk/pull/6363
