RFR: 8369393: NMT: poison the canaries of malloc header under ASAN build [v20]

[Afshin Zafari]

On Mon, 10 Nov 2025 10:36:20 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

> Makes sense, since we also want to catch one-byte-overwrites. Though I would probably just disable NMT and do it that way.

One big difference here is that NMT detects overflow/underflow only at free-ing the memory. Using ASAN poisoning, we can find the writer/reader immediately. Also, NMT reports the malloc-site (where in the source the memory is allocated) and we don't get any info about where in the code the corruption happened.

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PR Comment: https://git.openjdk.org/jdk/pull/27685#issuecomment-3510937980