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Fix buffer overrun in (test-only) symlink_junction

This commit is contained in:
Thom Chiovoloni 2023-04-05 00:37:30 -07:00
parent 540a50df0f
commit 6861750e66
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1 changed files with 25 additions and 9 deletions
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34
library/std/src/sys/windows/fs.rs
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@ -1403,24 +1403,40 @@ fn symlink_junction_inner(original: &Path, junction: &Path) -> io::Result<()> {
opts.custom_flags(c::FILE_FLAG_OPEN_REPARSE_POINT | c::FILE_FLAG_BACKUP_SEMANTICS);
let f = File::open(junction, &opts)?;
let h = f.as_inner().as_raw_handle();
unsafe {
let mut data = Align8([MaybeUninit::<u8>::uninit(); c::MAXIMUM_REPARSE_DATA_BUFFER_SIZE]);
let data_ptr = data.0.as_mut_ptr();
let data_end = data_ptr.add(c::MAXIMUM_REPARSE_DATA_BUFFER_SIZE);
let db = data_ptr.cast::<c::REPARSE_MOUNTPOINT_DATA_BUFFER>();
// Zero the header to ensure it's fully initialized, including reserved parameters.
*db = mem::zeroed();
let buf = ptr::addr_of_mut!((*db).ReparseTarget).cast::<c::WCHAR>();
let mut i = 0;
let reparse_target_slice = {
let buf_start = ptr::addr_of_mut!((*db).ReparseTarget).cast::<c::WCHAR>();
// Compute offset in bytes and then divide so that we round down
// rather than hit any UB (admittedly this arithmetic should work
// out so that this isn't necessary)
let buf_len_bytes = usize::try_from(data_end.byte_offset_from(buf_start)).unwrap();
let buf_len_wchars = buf_len_bytes / core::mem::size_of::<c::WCHAR>();
core::slice::from_raw_parts_mut(buf_start, buf_len_wchars)
};
// FIXME: this conversion is very hacky
let v = br"\??\";
let v = v.iter().map(|x| *x as u16);
for c in v.chain(original.as_os_str().encode_wide()) {
*buf.add(i) = c;
let iter = br"\??\"
.iter()
.map(|x| *x as u16)
.chain(original.as_os_str().encode_wide())
.chain(core::iter::once(0));
let mut i = 0;
for c in iter {
if i >= reparse_target_slice.len() {
return Err(crate::io::const_io_error!(
crate::io::ErrorKind::InvalidFilename,
"Input filename is too long"
));
}
reparse_target_slice[i] = c;
i += 1;
}
*buf.add(i) = 0;
i += 1;
(*db).ReparseTag = c::IO_REPARSE_TAG_MOUNT_POINT;
(*db).ReparseTargetMaximumLength = (i * 2) as c::WORD;
(*db).ReparseTargetLength = ((i - 1) * 2) as c::WORD;