RFR: 8275846: read_base_archive_name() could read past the end of buffer [v2]

[Ioi Lam]

> Please review this small fix for an intermittent crash in `FileHeaderHelper::read_base_archive_name()`. The crash happens if a string stored inside a CDS dynamic archive is not zero-terminated.
> 
> The fix is to check for zero-termination, and that the actual string length matches with the the recorded length.
> 
> This fix was authored by @yqi in PR #5997 , but that PR may take longer to integrate than expected. So let's fix the crash first.

Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:

  Added new test case where base archive does not exist

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6285/files
  - new: https://git.openjdk.java.net/jdk/pull/6285/files/87b31fae..59b9721b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6285&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6285&range=00-01

  Stats: 19 lines in 1 file changed: 19 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6285.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6285/head:pull/6285

PR: https://git.openjdk.java.net/jdk/pull/6285