Use after free in Neon externally allocated JavaScript buffers (#1256)

Author: kjvalencik

crates/neon/RUSTSEC-0000-0000.md

@@ -0,0 +1,38 @@
+```toml
+[advisory]
+id = "RUSTSEC-0000-0000"
+package = "neon"
+date = "2022-05-22"
+url = "https://github.com/neon-bindings/neon/issues/896"
+categories = ["memory-corruption", "memory-exposure"]
+keywords = ["use-after-free", "incorrect-lifetime"]
+
+[affected.functions]
+"neon::types::JsArrayBuffer::external" = ["< 0.10.1, >= 0.8.0"]
+"neon::types::JsBuffer::external" = ["< 0.10.1, >= 0.8.0"]
+
+[versions]
+patched = [">= 0.10.1"]
+unaffected = ["< 0.8.0"]
+```
+
+# Use after free in Neon external buffers
+
+Neon provides functionality for creating JavaScript `ArrayBuffer` (and the `Buffer` subtype) instances backed by bytes allocated outside of V8/Node. The [`JsArrayBuffer::external`](https://docs.rs/neon/0.10.0/neon/types/struct.JsArrayBuffer.html#method.external) and [`JsBuffer::external`](https://docs.rs/neon/0.10.0/neon/types/struct.JsBuffer.html#method.external) did not require `T: 'static` prior to Neon `0.10.1`. This allowed creating an externally backed buffer from types that may be freed while they are still referenced by a JavaScript `ArrayBuffer`.
+
+The following example demonstrates use after free. It compiles on versions `<0.10.1` and fails to compile afterward.
+
+```rust
+pub fn soundness_hole(mut cx: FunctionContext) -> JsResult<JsArrayBuffer> {
+    let mut data = vec![0u8, 1, 2, 3];
+    
+    // Creating an external from `&mut [u8]` instead of `Vec<u8>` since there is a blanket impl
+    // of `AsMut<T> for &mut T`
+    let buf = JsArrayBuffer::external(&mut cx, data.as_mut_slice());
+
+    // `buf` is still holding a reference to `data`!
+    drop(data);
+
+    Ok(buf)
+}
+```