reject growable SharedArrayBuffer without hooks#1523
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jdcaperon
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saghul
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Jun 2, 2026
| assert(!JS_IsException(ret)); | ||
| JS_FreeValue(ctx, ret); | ||
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| ret = eval(ctx, "new SharedArrayBuffer(16, { maxByteLength: 16 })"); |
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Should this succeed, since the current size if the same as the max?
| "const u8 = new Uint8Array(sab);" | ||
| "sab.grow(16384);" | ||
| "u8[1024] === 0 && u8.byteLength === 16384"); | ||
| assert(JS_IsBool(ret)); |
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Maybe for completeness assert that it's not an exception
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saghul
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Thanks! |
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This PR is AI assisted and human reviewed to the limits of the human, feel free to close and I can re-raise as an issue.
In
quickjs.c,js_array_buffer_constructor3()allowed growableSharedArrayBufferconstruction without SAB allocator hooks.Context
Growable
SharedArrayBufferconstruction could succeed on runtimes created withJS_NewRuntime()when the embedder had not installed SharedArrayBuffer allocator hooks.In that configuration, construction allocated only the initial
byteLength, whileSharedArrayBuffer.prototype.grow()later assumed the backing store coveredmaxByteLengthand only updated the logical byte length.That mismatch could let typed array and DataView access reach beyond the native allocation after growth.
Intent
Fail closed during JS-created growable
SharedArrayBufferconstruction whensab_allocis unavailable.Fixed-length
SharedArrayBufferconstruction remains allowed without hooks. Runtimes that install SAB allocator hooks can still construct and grow SABs backed by the upfrontmaxByteLengthallocation.The C API regression coverage checks the default-runtime rejection path, preserves fixed-length SAB behavior, and verifies hooked-runtime growth exposes zero-filled bytes beyond the initial length.