On Fri, 12 Nov 2021 08:25:04 GMT, Thomas Stuefe <stu...@openjdk.org> wrote:
> 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) This pull request has now been integrated. Changeset: b8d33a2a Author: Thomas Stuefe <stu...@openjdk.org> URL: https://git.openjdk.java.net/jdk/commit/b8d33a2a4e4ac1be322644102e8f09ce1435b4fb Stats: 9 lines in 3 files changed: 3 ins; 0 del; 6 mod 8277029: JMM GetDiagnosticXXXInfo APIs should verify output array sizes Reviewed-by: dholmes, sspitsyn ------------- PR: https://git.openjdk.java.net/jdk/pull/6363
