fix(napi): Read reference ownership before calling finalizer to avoid crash #24203
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devsnek
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Jun 13, 2024
bartlomieju
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Jun 18, 2024
… crash (#24203) Fixes #23493. What was happening here was that napi-rs was freeing the napi reference ([here](https://github.com/napi-rs/napi-rs/blob/19e3488efcbc601afa1f11a979372eb6c5ea6130/crates/napi/src/bindgen_runtime/mod.rs#L62)) during its finalize callback (which we call [here](https://github.com/denoland/deno/blob/fb31eaa9ca59f6daaee0210d5cd206185c7041b9/cli/napi/js_native_api.rs#L132)). We then were [reading the `ownership` field](https://github.com/denoland/deno/blob/fb31eaa9ca59f6daaee0210d5cd206185c7041b9/cli/napi/js_native_api.rs#L136) of that freed reference. For some reason on arm macs the freed memory gets zeroed, so the value of `ownership` was `0` when we read it (i.e. it was `ReferenceOwnership::Runtime`). We then freed it again (since we thought we owned it), causing the segfault.
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Fixes #23493.
What was happening here was that napi-rs was freeing the napi reference (here) during its finalize callback (which we call here). We then were reading the
ownershipfield of that freed reference.For some reason on arm macs the freed memory gets zeroed, so the value of
ownershipwas0when we read it (i.e. it wasReferenceOwnership::Runtime). We then freed it again (since we thought we owned it), causing the segfault.