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Fix debug runtime overflow and unaligned unwind metadata access #1184

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Fix debug runtime overflow and unaligned unwind metadata access #1184

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0bb02d3
Fix debug runtime overflow and unaligned unwind metadata access
May 10, 2026
43bb8c0
Merge remote-tracking branch 'origin/main' into fix-debug-misaligned-…
May 10, 2026
d5a85eb
Format lind-multi-process changes
May 10, 2026
f358000
Fix jmp_buf hash access in asyncify setjmp handling
May 11, 2026
154ffb0
Use aligned asyncify metadata access where possible
May 25, 2026
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24 changes: 13 additions & 11 deletions src/wasmtime/crates/lind-multi-process/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -356,7 +356,7 @@ impl<
// word), making start > end and firing the bounds-check ud2 every time.
*(unwind_data_start_sys as *mut u32) =
(unwind_data_start_usr + UNWIND_METADATA_SIZE) as u32;
*((unwind_data_start_sys + 4) as *mut u32) = stack_pointer as u32;
*((unwind_data_start_sys + 4) as *mut u32) = stack_pointer;
}

let get_cx = self.get_cx.clone();
Expand Down Expand Up @@ -887,7 +887,7 @@ impl<
unsafe {
*(parent_unwind_data_start_sys as *mut u32) =
(parent_unwind_data_start_usr + UNWIND_METADATA_SIZE) as u32;
*((parent_unwind_data_start_sys + 4) as *mut u32) = stack_pointer as u32;
*((parent_unwind_data_start_sys + 4) as *mut u32) = stack_pointer;
}

// set up child_tid
Expand Down Expand Up @@ -968,7 +968,7 @@ impl<
store.set_on_called(Box::new(move |mut store| {
// once unwind is finished, buf[0] (u32) holds the final write position
let parent_unwind_data_end_usr =
unsafe { *(parent_unwind_data_start_sys as *mut u32) } as u64;
unsafe { *(parent_unwind_data_start_sys as *const u32) } as u64;

// unwind finished and we need to stop the unwind
let _res = asyncify_stop_unwind_func.call(&mut store, ());
Expand Down Expand Up @@ -1459,7 +1459,7 @@ impl<
unsafe {
*(parent_unwind_data_start_sys as *mut u32) =
(parent_unwind_data_start_usr + UNWIND_METADATA_SIZE) as u32;
*((parent_unwind_data_start_sys + 4) as *mut u32) = stack_pointer as u32;
*((parent_unwind_data_start_sys + 4) as *mut u32) = stack_pointer;
}

// mark the start of unwind
Expand Down Expand Up @@ -1580,7 +1580,7 @@ impl<
unsafe {
*(parent_unwind_data_start_sys as *mut u32) =
(parent_unwind_data_start_usr + UNWIND_METADATA_SIZE) as u32;
*((parent_unwind_data_start_sys + 4) as *mut u32) = stack_pointer as u32;
*((parent_unwind_data_start_sys + 4) as *mut u32) = stack_pointer;
}

// mark the start of unwind
Expand Down Expand Up @@ -1655,7 +1655,7 @@ impl<
unsafe {
*(unwind_data_start_sys as *mut u32) =
(unwind_data_start_usr + UNWIND_METADATA_SIZE) as u32;
*((unwind_data_start_sys + 4) as *mut u32) = stack_pointer as u32;
*((unwind_data_start_sys + 4) as *mut u32) = stack_pointer;
}

// mark the start of unwind
Expand All @@ -1673,7 +1673,7 @@ impl<
let store = caller.as_context_mut().0;
store.set_on_called(Box::new(move |mut store| {
// once unwind is finished, buf[0] (u32) holds the final write position
let unwind_data_end_usr = unsafe { *(unwind_data_start_sys as *mut u32) } as u64;
let unwind_data_end_usr = unsafe { *(unwind_data_start_sys as *const u32) } as u64;

// unwind finished and we need to stop the unwind
let _res = asyncify_stop_unwind_func.call(&mut store, ());
Expand All @@ -1683,8 +1683,10 @@ impl<
// store the unwind data
let hash =
store.store_unwind_data(unwind_data_start_sys as *const u8, rewind_total_size);

let jmp_buf_sys = cloned_address + jmp_buf as u64;
unsafe {
std::ptr::write_unaligned((cloned_address + jmp_buf as u64) as *mut u64, hash);
std::ptr::write_unaligned(jmp_buf_sys as *mut u64, hash);
}

// mark the parent to rewind state
Expand Down Expand Up @@ -1733,7 +1735,7 @@ impl<
unsafe {
*(unwind_data_start_sys as *mut u32) =
(unwind_data_start_usr + UNWIND_METADATA_SIZE) as u32;
*((unwind_data_start_sys + 4) as *mut u32) = stack_pointer as u32;
*((unwind_data_start_sys + 4) as *mut u32) = stack_pointer;
}

// mark the start of unwind
Expand All @@ -1753,8 +1755,8 @@ impl<
// unwind finished and we need to stop the unwind
let _res = asyncify_stop_unwind_func.call(&mut store, ());

let hash =
unsafe { std::ptr::read_unaligned((cloned_address + jmp_buf as u64) as *mut u64) };
let jmp_buf_sys = cloned_address + jmp_buf as u64;
let hash = unsafe { std::ptr::read_unaligned(jmp_buf_sys as *const u64) };
// retrieve the unwind data
let data = store.retrieve_unwind_data(hash);

Expand Down