RFR: 8365604: Null pointer dereference in src/hotspot/share/adlc/output_h.cpp ArchDesc::declareClasses() [v2]

[Andrew Dinn]

On Thu, 21 Aug 2025 09:01:12 GMT, Artem Semenov <asemenov at openjdk.org> wrote:

>> The defect has been detected and confirmed in the function ArchDesc::declareClasses() located in the file src/hotspot/share/adlc/output_h.cpp with static code analysis. This defect can potentially lead to a null pointer dereference.
>> 
>> The pointer instr->_matrule is dereferenced in line 1952 without checking for nullptr, although earlier in line 1858 the same pointer is checked for nullptr, which indicates that it can be null.
>> 
>> According to [this](https://github.com/openjdk/jdk/pull/26002#issuecomment-3023050372) comment, this PR contains fixes for similar cases in other places.
>
> Artem Semenov has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Update src/hotspot/share/c1/c1_LinearScan.cpp
>    
>    Co-authored-by: David Holmes <62092539+dholmes-ora at users.noreply.github.com>
>  - Update src/hotspot/share/adlc/output_h.cpp
>    
>    Co-authored-by: David Holmes <62092539+dholmes-ora at users.noreply.github.com>

n.b. Before accepting any of the changes in this PR I'd really like to know whether they have arisen from reports of an actual null pointer dereference or they are simply derived from some theoretical analysis. In the latter case then I think we would need a better explanation of why an error can happen than we have seen so far. Given that requirement I also think each of the changes should be submitted in its own PR with its own justification. We should not modify control flow logic on the nod.

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

PR Comment: https://git.openjdk.org/jdk/pull/26798#issuecomment-3209906082