RFR: 8369393: NMT: poison the canaries of malloc header under ASAN build [v21]

[Paul Hübner]

On Mon, 10 Nov 2025 20:03:35 GMT, Afshin Zafari <azafari at openjdk.org> wrote:

>> NMT can detect malloc'd memory corruption using canary tests at header and footer of every memory region. This can only be done at free time of the memory where NNT checks the canaries and report error if they are not as expected.
>> In this PR, the canary parts also are poisoned using ASAN API to get notified whenever a read/write op is done. on the canary parts. `_size` member of the malloc header is also poisoned, since it is used for finding the footer address.
>
> Afshin Zafari has updated the pull request incrementally with one additional commit since the last revision:
> 
>   improvements.

Thanks again for doing this.

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Marked as reviewed by phubner (Author).

PR Review: https://git.openjdk.org/jdk/pull/27685#pullrequestreview-3458594894