fix(ext/ffi): retain backing store references in nonblocking calls#32775
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bartlomieju merged 2 commits intomainfrom Mar 16, 2026
Merged
fix(ext/ffi): retain backing store references in nonblocking calls#32775bartlomieju merged 2 commits intomainfrom
bartlomieju merged 2 commits intomainfrom
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Nonblocking FFI calls extract raw pointers from ArrayBuffer backing stores and send them to a background thread via spawn_blocking, but without retaining a reference to the backing store. If V8's garbage collector runs before the background thread completes, the backing store can be freed, leaving the native code with a dangling pointer. Fix by collecting SharedRef<BackingStore> references alongside the raw pointers for buffer, struct, and out_buffer arguments in nonblocking calls, and moving them into the spawn_blocking closure so they are kept alive for the duration of the native call. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
kajukitli
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Mar 16, 2026
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lgtm — solid fix for the UAF in nonblocking FFI
the BackingStoreHolder pattern is clean: grab SharedRef<BackingStore> before extracting raw pointers, move holder into the spawn_blocking closure, explicit drop() after the call to make intent clear
test coverage is good: fills buffer with known pattern, forces GC while native sleeps, validates checksum on return
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Nonblocking FFI calls extract raw pointers from ArrayBuffer backing stores and send them to a background thread via spawn_blocking, but without retaining a reference to the backing store. If V8's garbage collector runs before the background thread completes, the backing store can be freed, leaving the native code with a dangling pointer.
Fix by collecting SharedRef references alongside the raw pointers for buffer, struct, and out_buffer arguments in nonblocking calls, and moving them into the spawn_blocking closure so they are kept alive for the duration of the native call.