RFR: 8368097: [asan] heap-buffer-overflow reported in ClassFileParser::skip_over_field_signature [v2]

[Johan Sjölen]

> Hi,
> 
> `skip_over_field_name` may produce a pointer which is exactly one `char` of bounds, which is the dereferenced by `skip_over_field_signature` when it looks for a semi-colon. This causes an out-of-bounds read, which ASAN caught. The fix is to check whether it's OK to dereference `p` or not.
> 
> We keep the semantics the same other than that, so `skip_over_field_signature` and `skip_over_field_name` can both return a pointer which is one past the valid memory range. Creating such a pointer is explicitly not UB, but dereferencing it is.

Johan Sjölen has updated the pull request incrementally with one additional commit since the last revision:

  Update src/hotspot/share/classfile/classFileParser.cpp
  
  Co-authored-by: David Holmes <62092539+dholmes-ora at users.noreply.github.com>

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27528/files
  - new: https://git.openjdk.org/jdk/pull/27528/files/75709361..f6b89402

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27528&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27528&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/27528.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27528/head:pull/27528

PR: https://git.openjdk.org/jdk/pull/27528