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Avoid overflow in component ABI size calculations #14058

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3fc2cab
Avoid overflow in component ABI size calculations
subotac Aug 1, 2026
3ca57dd
Narrow canonical ABI overflow handling
subotac Aug 3, 2026
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54 changes: 36 additions & 18 deletions crates/environ/src/component/types.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -645,11 +645,11 @@ pub enum InterfaceType {
/// memory32 and memory64-based types.
#[derive(Serialize, Deserialize, Clone, Hash, Eq, PartialEq, Debug)]
pub struct CanonicalAbiInfo {
/// The byte-size of this type in a 32-bit memory.
/// The byte-size of this type in a 32-bit memory, saturated at [`u32::MAX`].
pub size32: u32,
/// The byte-alignment of this type in a 32-bit memory.
pub align32: u32,
/// The byte-size of this type in a 64-bit memory.
/// The byte-size of this type in a 64-bit memory, saturated at [`u32::MAX`].
pub size64: u32,
/// The byte-alignment of this type in a 64-bit memory.
pub align64: u32,
Expand Down Expand Up @@ -679,6 +679,24 @@ const fn align_to(a: u32, b: u32) -> u32 {
(a + (b - 1)) & !(b - 1)
}

const fn saturating_size(size: u64) -> u32 {
if size > u32::MAX as u64 {
u32::MAX
} else {
size as u32
}
}

const fn align_size_to(size: u32, align: u32) -> u32 {
assert!(align.is_power_of_two());
let align = align as u64;
saturating_size((size as u64 + (align - 1)) & !(align - 1))
}

const fn add_sizes(a: u32, b: u32) -> u32 {
saturating_size(a as u64 + b as u64)
}

const fn max(a: u32, b: u32) -> u32 {
if a > b { a } else { b }
}
Expand Down Expand Up @@ -728,14 +746,14 @@ impl CanonicalAbiInfo {

let mut ret = CanonicalAbiInfo::default();
for field in fields {
ret.size32 = align_to(ret.size32, field.align32) + field.size32;
ret.size32 = add_sizes(align_size_to(ret.size32, field.align32), field.size32);
ret.align32 = ret.align32.max(field.align32);
ret.size64 = align_to(ret.size64, field.align64) + field.size64;
ret.size64 = add_sizes(align_size_to(ret.size64, field.align64), field.size64);
ret.align64 = ret.align64.max(field.align64);
ret.flat_count = add_flat(ret.flat_count, field.flat_count);
}
ret.size32 = align_to(ret.size32, ret.align32);
ret.size64 = align_to(ret.size64, ret.align64);
ret.size32 = align_size_to(ret.size32, ret.align32);
ret.size64 = align_size_to(ret.size64, ret.align64);
return ret;
}

Expand All @@ -748,15 +766,15 @@ impl CanonicalAbiInfo {
let mut i = 0;
while i < fields.len() {
let field = &fields[i];
ret.size32 = align_to(ret.size32, field.align32) + field.size32;
ret.size32 = add_sizes(align_size_to(ret.size32, field.align32), field.size32);
ret.align32 = max(ret.align32, field.align32);
ret.size64 = align_to(ret.size64, field.align64) + field.size64;
ret.size64 = add_sizes(align_size_to(ret.size64, field.align64), field.size64);
ret.align64 = max(ret.align64, field.align64);
ret.flat_count = add_flat(ret.flat_count, field.flat_count);
i += 1;
}
ret.size32 = align_to(ret.size32, ret.align32);
ret.size64 = align_to(ret.size64, ret.align64);
ret.size32 = align_size_to(ret.size32, ret.align32);
ret.size64 = align_size_to(ret.size64, ret.align64);
return ret;
}

Expand Down Expand Up @@ -874,13 +892,13 @@ impl CanonicalAbiInfo {
}
}
CanonicalAbiInfo {
size32: align_to(
align_to(discrim_size, max_align32) + max_size32,
size32: align_size_to(
add_sizes(align_size_to(discrim_size, max_align32), max_size32),
max_align32,
),
align32: max_align32,
size64: align_to(
align_to(discrim_size, max_align64) + max_size64,
size64: align_size_to(
add_sizes(align_size_to(discrim_size, max_align64), max_size64),
max_align64,
),
align64: max_align64,
Expand Down Expand Up @@ -915,13 +933,13 @@ impl CanonicalAbiInfo {
i += 1;
}
CanonicalAbiInfo {
size32: align_to(
align_to(discrim_size, max_align32) + max_size32,
size32: align_size_to(
add_sizes(align_size_to(discrim_size, max_align32), max_size32),
max_align32,
),
align32: max_align32,
size64: align_to(
align_to(discrim_size, max_align64) + max_size64,
size64: align_size_to(
add_sizes(align_size_to(discrim_size, max_align64), max_size64),
max_align64,
),
align64: max_align64,
Expand Down
11 changes: 11 additions & 0 deletions tests/misc_testsuite/component-model/fixed_length_lists.wast
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,17 @@

;; Every mismatch increases the return value by 1.

;; Large fixed-length lists saturate cached ABI sizes instead of overflowing
;; when nested in a record.
(component
(component
(type $l (list u64 1073741824))
(type $t (tuple $l $l))
(type $f (func (param "a" $t)))
(import "x" (func (type $f)))
)
)

(component
(component (;0;)
(type $ty-test:fixed-size-lists/to-test (;0;)
Expand Down
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