path_open does not respect oflags::excl on directories

[yagehu]

Describe the bug

Calling path_open with oflags::creat and oflags::excl both set should fail if path points to an existing directory. Currently, Wasmer successfully open the directory and returns a valid fd.

$ wasmer -vV; rustc -vV
wasmer 4.3.1 (3930278 2024-05-31)
binary: wasmer-cli
commit-hash: 3930278b2e98528224ebf891f220aeacf2ec32db
commit-date: 2024-05-31
host: x86_64-apple-darwin
compiler: singlepass,cranelift
rustc 1.78.0 (9b00956e5 2024-04-29)
binary: rustc
commit-hash: 9b00956e56009bab2aa15d7bff10916599e3d6d6
commit-date: 2024-04-29
host: x86_64-apple-darwin
release: 1.78.0
LLVM version: 18.1.2

Steps to reproduce

Compile this Rust snippet with wasi v0.11. Create a directory dir before running. This snippet should fail, but Wasmer succeeds, returning a valid fd.

fn main() {
    unsafe {
        let fd = wasi::path_open(
            3,
            0,
            "dir",
            wasi::OFLAGS_CREAT | wasi::OFLAGS_EXCL,
            wasi::RIGHTS_FD_READ,
            0,
            0,
        )
        .unwrap();
        eprintln!("fd: {fd}");
    }
}

[yagehu]

Sorry for the noise. I think I was on a bad commit.

[yagehu]

I've reverted back to a good commit and this problem remains. I'll investigate and confirm with a wasi-fyi test case.

[yagehu]

Here's a wasi-fyi test that confirms the problem.

use std::ffi::CString;
use std::fs;

#[link(wasm_import_module = "wasi_snapshot_preview1")]
extern "C" {
    pub fn path_open(
        fd: i32,
        dirflags: i32,
        path: i32,
        path_len: i32,
        oflags: i32,
        fs_rights_base: i64,
        fs_rights_inheriting: i64,
        fdflags: i32,
        result_fd: i32,
    ) -> i32;
}

const ERRNO_SUCCESS: i32 = 0;
const ERRNO_EXIST: i32 = 20;
const OFLAGS_CREAT: i32 = 1;
const OFLAGS_EXCL: i32 = 4;
const RIGHTS_FD_READ: i64 = 2;
const RIGHTS_FD_WRITE: i64 = 64;

fn main() {
    unsafe {
        let fd = 5;
        let path0 = CString::new("fyi/fs_open_dir_excl.dir").unwrap();
        let path1 = CString::new("fyi/fs_open_dir_excl.dir/file").unwrap();
        let errno = path_open(
            fd,
            0,
            path0.as_ptr() as i32,
            path0.as_bytes().len() as i32,
            OFLAGS_CREAT | OFLAGS_EXCL,
            RIGHTS_FD_READ | RIGHTS_FD_WRITE,
            0,
            0,
            1024,
        );
        assert_eq!(
            errno, ERRNO_EXIST,
            "opening an existing directory with excl should fail"
        );

        let _ = fs::remove_file("/fyi/fs_open_dir_excl.dir/file");
        let errno = path_open(
            fd,
            0,
            path1.as_ptr() as i32,
            path1.as_bytes().len() as i32,
            OFLAGS_CREAT | OFLAGS_EXCL,
            RIGHTS_FD_READ | RIGHTS_FD_WRITE,
            0,
            0,
            1024,
        );
        assert_eq!(
            errno, ERRNO_SUCCESS,
            "opening a non-existing path with excl should succeed"
        );
    }
}