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vhdx: add some safety comments

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Also add some assertions to some places along side the safety comments.

Signed-off-by: Wei Liu <liuwe@microsoft.com>
This commit is contained in:
Wei Liu 2022-11-16 17:28:15 +00:00 committed by Liu Wei
parent 1d9050dbe3
commit b9ad3eda27
2 changed files with 9 additions and 0 deletions
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5
vhdx/src/vhdx_header.rs
View File

@ -136,6 +136,7 @@ impl Header {
f.read_exact(&mut buffer)
.map_err(VhdxHeaderError::ReadHeader)?;
// SAFETY: buffer is of correct size and has been successfully filled.
let header = unsafe { *(buffer.as_ptr() as *mut Header) };
if header.signature != HEADER_SIGN {
return Err(VhdxHeaderError::InvalidHeaderSign);
@ -151,6 +152,7 @@ impl Header {
/// Converts the header structure into a buffer
fn get_header_as_buffer(&self, buffer: &mut [u8; HEADER_SIZE as usize]) {
// SAFETY: self is a valid header.
let reference = unsafe {
std::slice::from_raw_parts(self as *const Header as *const u8, HEADER_SIZE as usize)
};
@ -221,6 +223,7 @@ impl RegionTableHeader {
f.read_exact(&mut buffer)
.map_err(VhdxHeaderError::ReadRegionTableHeader)?;
// SAFETY: buffer is of correct size and has been successfully filled.
let region_table_header = unsafe { *(buffer.as_ptr() as *mut RegionTableHeader) };
if region_table_header.signature != REGION_SIGN {
return Err(VhdxHeaderError::InvalidRegionSign);
@ -337,6 +340,8 @@ pub struct RegionTableEntry {
impl RegionTableEntry {
/// Reads one Region Entry from a Region Table index that starts from 0
pub fn new(buffer: &[u8]) -> Result<RegionTableEntry> {
assert!(buffer.len() == std::mem::size_of::<RegionTableEntry>());
// SAFETY: the assertion above makes sure the buffer size is correct.
let mut region_table_entry = unsafe { *(buffer.as_ptr() as *mut RegionTableEntry) };
let uuid = crate::uuid_from_guid(buffer);

4
vhdx/src/vhdx_metadata.rs
View File

@ -270,6 +270,8 @@ struct MetadataTableHeader {
impl MetadataTableHeader {
pub fn new(buffer: &[u8]) -> Result<MetadataTableHeader> {
assert!(buffer.len() == std::mem::size_of::<MetadataTableHeader>());
// SAFETY: the assertion above makes sure the buffer size is correct.
let metadata_table_header = unsafe { *(buffer.as_ptr() as *mut MetadataTableHeader) };
if metadata_table_header.signature != METADATA_SIGN {
@ -301,6 +303,8 @@ pub struct MetadataTableEntry {
impl MetadataTableEntry {
/// Parse one metadata entry from the buffer
fn new(buffer: &[u8]) -> Result<MetadataTableEntry> {
assert!(buffer.len() == std::mem::size_of::<MetadataTableEntry>());
// SAFETY: the assertion above makes sure the buffer size is correct.
let mut metadata_table_entry = unsafe { *(buffer.as_ptr() as *mut MetadataTableEntry) };
let uuid = crate::uuid_from_guid(buffer);