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fix(vm): use checked_mul and checked_add to avoid pre-check overflow #545

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fix(vm): use checked_mul and checked_add to avoid pre-check overflow #545

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16 changes: 8 additions & 8 deletions vm/src/memory/paged_memory.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -104,18 +104,18 @@ impl PagedMemory {
}

pub fn set_words(&mut self, address: u32, values: &[u32]) -> Result<(), MemoryError> {
if address
.checked_add(values.len() as u32 * WORD_SIZE as u32)
.is_none()
{
return Err(MemoryError::AddressCalculationOverflow);
}

if values.is_empty() {
return Ok(());
}

let end_address = address + values.len() as u32 * WORD_SIZE as u32;
let words_len_u32 =
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@sjudson sjudson Nov 26, 2025

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We freely swap between u32 and usize throughout the codebase, due to the fact that it is a RISC-V32 processor this is essentially always safe. So that's much cleaner and I'd recommend just doing the cast here.

u32::try_from(values.len()).map_err(|_| MemoryError::AddressCalculationOverflow)?;
let bytes_len = words_len_u32
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@sjudson sjudson Nov 26, 2025

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You should be able to chain these cleanly using map_or_else.

.checked_mul(WORD_SIZE as u32)
.ok_or(MemoryError::AddressCalculationOverflow)?;
let end_address = address
.checked_add(bytes_len)
.ok_or(MemoryError::AddressCalculationOverflow)?;

let mut current_address = address;
let mut current_index = 0;
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