fix: use checked arithmetic in bounds_check! to prevent overflow bypass#1263
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ludfjig merged 1 commit intohyperlight-dev:mainfrom Feb 26, 2026
Merged
fix: use checked arithmetic in bounds_check! to prevent overflow bypass#1263ludfjig merged 1 commit intohyperlight-dev:mainfrom
ludfjig merged 1 commit intohyperlight-dev:mainfrom
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The bounds check silently wraps on usize overflow in release builds, bypassing the check entirely. Not exploitable today since callers validate offsets before reaching the macro, but any future caller that doesn't could trigger it. Signed-off-by: Ludvig Liljenberg <4257730+ludfjig@users.noreply.github.com>
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andreiltd
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jsturtevant
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Making the use of our helper functions easier to do the right thing properly is 💯
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Pull request overview
This PR hardens Hyperlight host shared-memory access by making the bounds_check! macro overflow-safe, preventing usize addition wraparound from bypassing bounds checks in release builds.
Changes:
- Update
bounds_check!to usechecked_addsooffset + sizeoverflow is treated as out-of-bounds. - Add a regression test that exercises overflow offsets/sizes across several
ExclusiveSharedMemoryandHostSharedMemoryAPIs.
Comments suppressed due to low confidence (2)
src/hyperlight_host/src/mem/shared_mem.rs:57
bounds_check!is used by both read and write/copy/fill paths in this file, but the error message hard-codes "Cannot read value...". This can be misleading when the failing operation is a write or fill; consider making the message operation-agnostic (e.g., "Cannot access memory...") or allowing the call site to supply an operation label.
if $offset.checked_add($size).is_none_or(|end| end > $mem_size) {
return Err(new_error!(
"Cannot read value from offset {} with size {} in memory of size {}",
$offset,
$size,
$mem_size
));
src/hyperlight_host/src/mem/shared_mem.rs:56
bounds_check!references$offset,$size, and$mem_sizemultiple times (in the check and again in the formatted error). If a caller ever passes expressions with side effects, they could be evaluated more than once. Consider binding the macro inputs to localletvariables inside the macro expansion so each argument is evaluated exactly once.
($offset:expr, $size:expr, $mem_size:expr) => {
if $offset.checked_add($size).is_none_or(|end| end > $mem_size) {
return Err(new_error!(
"Cannot read value from offset {} with size {} in memory of size {}",
$offset,
$size,
$mem_size
dblnz
approved these changes
Feb 26, 2026
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The bounds check silently wraps on usize overflow in release builds, bypassing the check entirely. Not exploitable today since callers validate offsets before reaching the macro, but any future caller that doesn't could trigger it.