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Limit async stream read/write lengths #1588

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Merged
alexcrichton merged 1 commit into from
Apr 14, 2026
+9 −2
Merged

Limit async stream read/write lengths #1588

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11 changes: 9 additions & 2 deletions crates/guest-rust/src/rt/async_support/stream_support.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,9 @@ use {
},
};

/// Maximum size of a read/write operation as specified by the canonical ABI.
const MAX_LENGTH: usize = (1 << 28) - 1;

/// Operations that a stream requires throughout the implementation.
///
/// This is generated by `wit_bindgen::generate!` primarily.
Expand Down Expand Up @@ -376,7 +379,11 @@ where
let (ptr, len) = buf.abi_ptr_and_len();
// SAFETY: sure hope this is safe, everything in this module and
// `AbiBuffer` is trying to make this safe.
let code = unsafe { self.writer.ops.start_write(self.writer.handle, ptr, len) };
let code = unsafe {
self.writer
.ops
.start_write(self.writer.handle, ptr, len.min(MAX_LENGTH))
};
rtdebug!(
"stream.write({}, {ptr:?}, {len}) = {code:#x}",
self.writer.handle
Expand Down Expand Up @@ -618,7 +625,7 @@ unsafe impl<'a, O: StreamOps> WaitableOp for StreamReadOp<'a, O> {
let code = unsafe {
self.reader
.ops
.start_read(self.reader.handle(), ptr, cap.len())
.start_read(self.reader.handle(), ptr, cap.len().min(MAX_LENGTH))
};
rtdebug!(
"stream.read({}, {ptr:?}, {}) = {code:#x}",
Expand Down
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