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Allow WASI to open directories without O_DIRECTORY (#6163)

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* Allow WASI to open directories without O_DIRECTORY

The `O_DIRECTORY` flag is a request that open should fail if the named
path is not a directory. Opening a path which turns out to be a
directory is not supposed to fail if this flag is not specified.
However, wasi-common required callers to use it when opening
directories.

With this PR, we always open the path the same way whether or not the
`O_DIRECTORY` flag is specified. However, after opening it, we `stat` it
to check whether it turned out to be a directory, and determine which
operations the file descriptor should support accordingly. In addition,
we explicitly check whether the precondition defined by `O_DIRECTORY` is
satisfied.

Closes #4947 and closes #4967, which were earlier attempts at fixing the
same issue, but which had race conditions.

prtest:full

* Add tests from #4967/#4947

This test was authored by Roman Volosatovs <rvolosatovs@riseup.net> as
part of #4947.

* Tests: Close FDs before trying to unlink files

On Windows, when opening a path which might be a directory using
`CreateFile`, cap-primitives also removes the `FILE_SHARE_DELETE` mode.

That means that if we implement WASI's `path_open` such that it always
uses `CreateFile` on Windows, for both files and directories, then
holding an open file handle prevents deletion of that file.

So I'm changing these test programs to make sure they've closed the
handle before trying to delete the file.
This commit is contained in:
Jamey Sharp
2023-04-21 09:55:35 -07:00
committed by GitHub
parent 91d1d246cd
commit efdfc361f8
8 changed files with 170 additions and 93 deletions
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69
crates/wasi-common/cap-std-sync/src/dir.rs
View File

@@ -1,18 +1,24 @@
use crate::file::{filetype_from, File};
use cap_fs_ext::{DirEntryExt, DirExt, MetadataExt, SystemTimeSpec};
use cap_fs_ext::{DirEntryExt, DirExt, MetadataExt, OpenOptionsMaybeDirExt, SystemTimeSpec};
use cap_std::fs;
use std::any::Any;
use std::path::{Path, PathBuf};
use system_interface::fs::GetSetFdFlags;
use wasi_common::{
dir::{ReaddirCursor, ReaddirEntity, WasiDir},
file::{FdFlags, FileType, Filestat, OFlags, WasiFile},
file::{FdFlags, FileType, Filestat, OFlags},
Error, ErrorExt,
};
pub struct Dir(cap_std::fs::Dir);
pub struct Dir(fs::Dir);
pub enum OpenResult {
File(File),
Dir(Dir),
}
impl Dir {
pub fn from_cap_std(dir: cap_std::fs::Dir) -> Self {
pub fn from_cap_std(dir: fs::Dir) -> Self {
Dir(dir)
}
@@ -24,10 +30,11 @@ impl Dir {
read: bool,
write: bool,
fdflags: FdFlags,
) -> Result<File, Error> {
) -> Result<OpenResult, Error> {
use cap_fs_ext::{FollowSymlinks, OpenOptionsFollowExt};
let mut opts = cap_std::fs::OpenOptions::new();
let mut opts = fs::OpenOptions::new();
opts.maybe_dir(true);
if oflags.contains(OFlags::CREATE | OFlags::EXCLUSIVE) {
opts.create_new(true);
@@ -71,22 +78,31 @@ impl Dir {
return Err(Error::not_supported().context("SYNC family of FdFlags"));
}
if oflags.contains(OFlags::DIRECTORY) {
if oflags.contains(OFlags::CREATE)
|| oflags.contains(OFlags::EXCLUSIVE)
|| oflags.contains(OFlags::TRUNCATE)
{
return Err(Error::invalid_argument().context("directory oflags"));
}
}
let mut f = self.0.open_with(Path::new(path), &opts)?;
// NONBLOCK does not have an OpenOption either, but we can patch that on with set_fd_flags:
if fdflags.contains(wasi_common::file::FdFlags::NONBLOCK) {
let set_fd_flags = f.new_set_fd_flags(system_interface::fs::FdFlags::NONBLOCK)?;
f.set_fd_flags(set_fd_flags)?;
}
Ok(File::from_cap_std(f))
}
pub fn open_dir_(&self, symlink_follow: bool, path: &str) -> Result<Self, Error> {
let d = if symlink_follow {
self.0.open_dir(Path::new(path))?
if f.metadata()?.is_dir() {
Ok(OpenResult::Dir(Dir::from_cap_std(fs::Dir::from_std_file(
f.into_std(),
))))
} else if oflags.contains(OFlags::DIRECTORY) {
Err(Error::not_dir().context("expected directory but got file"))
} else {
self.0.open_dir_nofollow(Path::new(path))?
};
Ok(Dir::from_cap_std(d))
Ok(OpenResult::File(File::from_cap_std(f)))
}
}
pub fn rename_(&self, src_path: &str, dest_dir: &Self, dest_path: &str) -> Result<(), Error> {
@@ -120,14 +136,12 @@ impl WasiDir for Dir {
read: bool,
write: bool,
fdflags: FdFlags,
) -> Result<Box<dyn WasiFile>, Error> {
) -> Result<wasi_common::dir::OpenResult, Error> {
let f = self.open_file_(symlink_follow, path, oflags, read, write, fdflags)?;
Ok(Box::new(f))
}
async fn open_dir(&self, symlink_follow: bool, path: &str) -> Result<Box<dyn WasiDir>, Error> {
let d = self.open_dir_(symlink_follow, path)?;
Ok(Box::new(d))
match f {
OpenResult::File(f) => Ok(wasi_common::dir::OpenResult::File(Box::new(f))),
OpenResult::Dir(d) => Ok(wasi_common::dir::OpenResult::Dir(Box::new(d))),
}
}
async fn create_dir(&self, path: &str) -> Result<(), Error> {
@@ -327,6 +341,7 @@ fn convert_systimespec(t: Option<wasi_common::SystemTimeSpec>) -> Option<SystemT
mod test {
use super::Dir;
use cap_std::ambient_authority;
use wasi_common::file::{FdFlags, OFlags};
#[test]
fn scratch_dir() {
let tempdir = tempfile::Builder::new()
@@ -336,8 +351,16 @@ mod test {
let preopen_dir = cap_std::fs::Dir::open_ambient_dir(tempdir.path(), ambient_authority())
.expect("open ambient temporary dir");
let preopen_dir = Dir::from_cap_std(preopen_dir);
run(wasi_common::WasiDir::open_dir(&preopen_dir, false, "."))
.expect("open the same directory via WasiDir abstraction");
run(wasi_common::WasiDir::open_file(
&preopen_dir,
false,
".",
OFlags::empty(),
false,
false,
FdFlags::empty(),
))
.expect("open the same directory via WasiDir abstraction");
}
// Readdir does not work on windows, so we won't test it there.