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Fix UB in Windows DirBuffIter (provenance and alignment)

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This commit is contained in:
Thom Chiovoloni 2022-08-30 01:45:30 -07:00
parent 5c3490c901
commit c41f21b3e4
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1 changed files with 10 additions and 7 deletions
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17
library/std/src/sys/windows/fs.rs
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@ -658,18 +658,18 @@ impl File {
/// A buffer for holding directory entries.
struct DirBuff {
buffer: Vec<u8>,
buffer: Box<Align8<[u8; Self::BUFFER_SIZE]>>,
}
impl DirBuff {
const BUFFER_SIZE: usize = 1024;
fn new() -> Self {
const BUFFER_SIZE: usize = 1024;
Self { buffer: vec![0_u8; BUFFER_SIZE] }
Self { buffer: Box::new(Align8([0u8; Self::BUFFER_SIZE])) }
}
fn capacity(&self) -> usize {
self.buffer.len()
self.buffer.0.len()
}
fn as_mut_ptr(&mut self) -> *mut u8 {
self.buffer.as_mut_ptr().cast()
self.buffer.0.as_mut_ptr().cast()
}
/// Returns a `DirBuffIter`.
fn iter(&self) -> DirBuffIter<'_> {
@ -678,7 +678,7 @@ impl DirBuff {
}
impl AsRef<[u8]> for DirBuff {
fn as_ref(&self) -> &[u8] {
&self.buffer
&self.buffer.0
}
}
@ -706,9 +706,12 @@ impl<'a> Iterator for DirBuffIter<'a> {
// used to get the file name slice.
let (name, is_directory, next_entry) = unsafe {
let info = buffer.as_ptr().cast::<c::FILE_ID_BOTH_DIR_INFO>();
// Guaranteed to be aligned in documentation for
// https://docs.microsoft.com/en-us/windows/win32/api/winbase/ns-winbase-file_id_both_dir_info
assert!(info.is_aligned());
let next_entry = (*info).NextEntryOffset as usize;
let name = crate::slice::from_raw_parts(
(*info).FileName.as_ptr().cast::<u16>(),
ptr::addr_of!((*info).FileName).cast::<u16>(),
(*info).FileNameLength as usize / size_of::<u16>(),
);
let is_directory = ((*info).FileAttributes & c::FILE_ATTRIBUTE_DIRECTORY) != 0;