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Fix fd_readdir to properly truncate directory entry names. #2620

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merged 2 commits into from
Feb 1, 2021
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Fix fd_readdir to properly truncate directory entry names. #2620

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4632228
Fix `fd_readdir` to properly truncate directory entry names.
peterhuene Jan 28, 2021
0502cad
Stop allowing bufused > BUF_LEN in fd_readdir program.
peterhuene Jan 28, 2021
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6 changes: 4 additions & 2 deletions crates/test-programs/wasi-tests/src/bin/fd_readdir.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
use more_asserts::assert_gt;
use std::{cmp::min, env, mem, process, slice, str};
use std::{env, mem, process, slice, str};
use wasi_tests::open_scratch_directory;

const BUF_LEN: usize = 256;
Expand Down Expand Up @@ -59,7 +59,9 @@ unsafe fn exec_fd_readdir(fd: wasi::Fd, cookie: wasi::Dircookie) -> (Vec<DirEntr
let bufused =
wasi::fd_readdir(fd, buf.as_mut_ptr(), BUF_LEN, cookie).expect("failed fd_readdir");

let sl = slice::from_raw_parts(buf.as_ptr(), min(BUF_LEN, bufused));
assert!(bufused <= BUF_LEN);

let sl = slice::from_raw_parts(buf.as_ptr(), bufused);
let dirs: Vec<_> = ReadDir::from_slice(sl).collect();
let eof = bufused < BUF_LEN;
(dirs, eof)
Expand Down
5 changes: 2 additions & 3 deletions crates/wasi-common/src/snapshots/wasi_snapshot_preview1.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -304,7 +304,6 @@ impl<'a> WasiSnapshotPreview1 for WasiCtx {
let dirent_len: types::Size = dirent_raw.len().try_into()?;
let name_raw = name.as_bytes();
let name_len = name_raw.len().try_into()?;
let offset = dirent_len.checked_add(name_len).ok_or(Error::Overflow)?;

// Copy as many bytes of the dirent as we can, up to the end of the buffer.
let dirent_copy_len = min(dirent_len, buf_len - bufused);
Expand All @@ -318,6 +317,7 @@ impl<'a> WasiSnapshotPreview1 for WasiCtx {
}

buf = buf.add(dirent_copy_len)?;
bufused += dirent_copy_len;

// Copy as many bytes of the name as we can, up to the end of the buffer.
let name_copy_len = min(name_len, buf_len - bufused);
Expand All @@ -331,8 +331,7 @@ impl<'a> WasiSnapshotPreview1 for WasiCtx {
}

buf = buf.add(name_copy_len)?;

bufused += offset;
bufused += name_copy_len;
}

Ok(bufused)
Expand Down