RFR: JDK-8277029: JMM GetDiagnosticXXXInfo APIs should verify output array sizes [v2]
Thomas Stuefe
stuefe at openjdk.java.net
Tue Nov 16 06:26:08 UTC 2021
> 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)
Thomas Stuefe has updated the pull request incrementally with one additional commit since the last revision:
Remove changes to GetDiagnosticCommandInfo
-------------
Changes:
- all: https://git.openjdk.java.net/jdk/pull/6363/files
- new: https://git.openjdk.java.net/jdk/pull/6363/files/65dad518..3bdc6c89
Webrevs:
- full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6363&range=01
- incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6363&range=00-01
Stats: 9 lines in 3 files changed: 0 ins; 5 del; 4 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
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