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Fix pointer provenance in const serialize with zero sized type enum variants #3532

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merged 1 commit into from
Jan 10, 2025
Merged

Fix pointer provenance in const serialize with zero sized type enum variants #3532

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23 changes: 15 additions & 8 deletions packages/const-serialize/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,11 @@ impl EnumLayout {
i += 1;
}

let variants_offset = (discriminant.size / max_align) + max_align;
let variants_offset_raw = discriminant.size;
let padding = (max_align - (variants_offset_raw % max_align)) % max_align;
let variants_offset = variants_offset_raw + padding;

assert!(variants_offset % max_align == 0);

Self {
size,
Expand Down Expand Up @@ -588,7 +592,7 @@ const fn serialize_const_struct(
while i < layout.data.len() {
// Serialize the field at the offset pointer in the struct
let StructFieldLayout { offset, layout } = &layout.data[i];
let field = unsafe { ptr.byte_add(*offset) };
let field = ptr.wrapping_byte_add(*offset as _);
to = serialize_const_ptr(field, to, layout);
i += 1;
}
Expand All @@ -610,11 +614,11 @@ const fn serialize_const_enum(
let byte = if cfg!(target_endian = "big") {
unsafe {
byte_ptr
.byte_add(layout.discriminant.size - offset - 1)
.wrapping_byte_add((layout.discriminant.size - offset - 1) as _)
.read()
}
} else {
unsafe { byte_ptr.byte_add(offset).read() }
unsafe { byte_ptr.wrapping_byte_add(offset as _).read() }
};
to = to.push(byte);
discriminant |= (byte as u32) << (offset * 8);
Expand All @@ -626,7 +630,7 @@ const fn serialize_const_enum(
// If the variant is the discriminated one, serialize it
let EnumVariant { tag, data, .. } = &layout.variants[i];
if discriminant == *tag {
let data_ptr = unsafe { ptr.byte_add(layout.variants_offset) };
let data_ptr = ptr.wrapping_byte_offset(layout.variants_offset as _);
to = serialize_const_struct(data_ptr, to, data);
break;
}
Expand All @@ -646,9 +650,12 @@ const fn serialize_const_primitive(
while offset < layout.size {
// If the bytes are reversed, walk backwards from the end of the number when pushing bytes
if cfg!(any(target_endian = "big", feature = "test-big-endian")) {
to = to.push(unsafe { ptr.byte_add(layout.size - offset - 1).read() });
to = to.push(unsafe {
ptr.wrapping_byte_offset((layout.size - offset - 1) as _)
.read()
});
} else {
to = to.push(unsafe { ptr.byte_add(offset).read() });
to = to.push(unsafe { ptr.wrapping_byte_offset(offset as _).read() });
}
offset += 1;
}
Expand All @@ -664,7 +671,7 @@ const fn serialize_const_list(
let len = layout.len;
let mut i = 0;
while i < len {
let field = unsafe { ptr.byte_add(i * layout.item_layout.size()) };
let field = ptr.wrapping_byte_offset((i * layout.item_layout.size()) as _);
to = serialize_const_ptr(field, to, layout.item_layout);
i += 1;
}
Expand Down
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