sys: fs: set CLOEXEC when creating temp files

In general we want all open files to have set CLOEXEC since our
reloading mechanism can basically fork at any moment and we don't want
newer daemons to carry around old file descriptors, especially lock
files.

Since `make_tmp_file` is called by many things (e.g. open_file_locked,
logrotate, rrd), set O_CLOEXEC with mkostemp.

This fixes issues with leftover file descriptors e.g. tape backups not
working because of lingering locks after a reload, or having deleted
rrd files open.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
Reviewed-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>

proxmox-sys/src/fs/file.rs

@@ -116,6 +116,29 @@ pub fn file_read_firstline<P: AsRef<Path>>(path: P) -> Result<String, Error> {
     read_firstline(path).map_err(|err| format_err!("unable to read {path:?} - {err}"))
 }
 
+#[inline]
+/// Creates a tmpfile like [`nix::unistd::mkstemp`], but with [`nix::fctnl::Oflag`] set.
+///
+/// Note that some flags are masked out since they can produce an error, see mkostemp(2) for details.
+// code is mostly copied from nix mkstemp
+fn mkostemp<P: ?Sized + NixPath>(
+    template: &P,
+    oflag: OFlag,
+) -> nix::Result<(std::os::fd::RawFd, PathBuf)> {
+    use std::os::unix::ffi::OsStringExt;
+    let mut path = template.with_nix_path(|path| path.to_bytes_with_nul().to_owned())?;
+    let p = path.as_mut_ptr().cast();
+
+    let flags = OFlag::intersection(OFlag::O_APPEND | OFlag::O_CLOEXEC | OFlag::O_SYNC, oflag);
+
+    let fd = unsafe { libc::mkostemp(p, flags.bits()) };
+    let last = path.pop(); // drop the trailing nul
+    debug_assert!(last == Some(b'\0'));
+    let pathname = std::ffi::OsString::from_vec(path);
+    Errno::result(fd)?;
+    Ok((fd, PathBuf::from(pathname)))
+}
+
 /// Takes a Path and CreateOptions, creates a tmpfile from it and returns
 /// a RawFd and PathBuf for it
 pub fn make_tmp_file<P: AsRef<Path>>(
@@ -127,7 +150,7 @@ pub fn make_tmp_file<P: AsRef<Path>>(
     // use mkstemp here, because it works with different processes, threads, even tokio tasks
     let mut template = path.to_owned();
     template.set_extension("tmp_XXXXXX");
-    let (mut file, tmp_path) = match unistd::mkstemp(&template) {
+    let (mut file, tmp_path) = match mkostemp(&template, OFlag::O_CLOEXEC) {
         Ok((fd, path)) => (unsafe { File::from_raw_fd(fd) }, path),
         Err(err) => bail!("mkstemp {:?} failed: {}", template, err),
     };