change cd to handle not readable directories: chdir+open instead of open+fchdir

CHANGELOG.rst

@@ -146,6 +146,7 @@ Other improvements
 - ``fish_indent`` will now collapse multiple successive empty lines into one (:issue:`10325`).
 - The HTML-based configuration UI (``fish_config``) now uses Alpine.js instead of AngularJS (:issue:`9554`).
 - ``fish_config`` now also works in a Windows MSYS environment (:issue:`10111`).
+- `cd` into a directory that is not readable but accessile (permissions `--x`) is now possible (:issue:`10432`).
 
 .. _rust-packaging:
 

src/builtins/cd.rs

@@ -2,15 +2,14 @@
 
 use super::prelude::*;
 use crate::{
+ common::wcs2zstring,
  env::{EnvMode, Environment},
- fds::wopen_dir,
  path::path_apply_cdpath,
  wutil::{normalize_path, wperror, wreadlink},
 };
 use errno::Errno;
-use libc::{fchdir, EACCES, ELOOP, ENOENT, ENOTDIR, EPERM};
-use nix::sys::stat::Mode;
-use std::{os::fd::AsRawFd, sync::Arc};
+use libc::{EACCES, ELOOP, ENOENT, ENOTDIR, EPERM};
+use nix::unistd::chdir;
 
 // The cd builtin. Changes the current directory to the one specified or to $HOME if none is
 // specified. The directory can be relative to any directory in the CDPATH variable.
@@ -87,18 +86,10 @@ pub fn cd(parser: &Parser, streams: &mut IoStreams, args: &mut [&wstr]) -> Optio
 
  errno::set_errno(Errno(0));
 
- let res = wopen_dir(&norm_dir, Mode::empty()).map_err(|err| err as i32);
+ let res = chdir(wcs2zstring(&norm_dir).as_c_str()).map_err(|e| e as i32);
 
- let res = res.and_then(|fd| {
- if unsafe { fchdir(fd.as_raw_fd()) } == 0 {
- Ok(fd)
- } else {
- Err(errno::errno().0)
- }
- });
-
- let fd = match res {
- Ok(fd) => fd,
+ match res {
+ Ok(_) => {}
  Err(err) => {
  // Some errors we skip and only report if nothing worked.
  // ENOENT in particular is very low priority
@@ -122,13 +113,10 @@ pub fn cd(parser: &Parser, streams: &mut IoStreams, args: &mut [&wstr]) -> Optio
  best_errno = err;
  break;
  }
- };
+ }
 
  // We need to keep around the fd for this directory, in the parser.
- let dir_fd = Arc::new(fd);
-
- // Stash the fd for the cwd in the parser.
- parser.libdata_mut().cwd_fd = Some(dir_fd);
+ parser.libdata_mut().update_cwd_fd();
 
  parser.set_var_and_fire(L!("PWD"), EnvMode::EXPORT | EnvMode::GLOBAL, vec![norm_dir]);
  return STATUS_CMD_OK;

src/parser.rs

@@ -239,6 +239,18 @@ impl LibraryData {
  ..Default::default()
  }
  }
+
+ pub fn update_cwd_fd(&mut self) {
+ match open_dir(CStr::from_bytes_with_nul(b".\0").unwrap(), Mode::empty()) {
+ Ok(fd) => {
+ self.cwd_fd = Some(Arc::new(fd));
+ }
+ Err(_) => {
+ perror("Unable to open the current working directory");
+ self.cwd_fd = None;
+ }
+ }
+ }
 }
 
 impl Default for LoopStatus {
@@ -353,14 +365,7 @@ impl Parser {
  global_event_blocks: AtomicU64::new(0),
  });
 
- match open_dir(CStr::from_bytes_with_nul(b".\0").unwrap(), Mode::empty()) {
- Ok(fd) => {
- result.libdata_mut().cwd_fd = Some(Arc::new(fd));
- }
- Err(_) => {
- perror("Unable to open the current working directory");
- }
- }
+ result.libdata_mut().update_cwd_fd();
 
  result
  }

tests/checks/cd.fish

@@ -271,3 +271,27 @@ end
 complete -C'cd .'
 # CHECK: ../
 # CHECK: ./
+
+# Check that cd works with minimal permissions (issue #10432)
+begin
+ set -l oldpwd (pwd)
+ set -l tmp (mktemp -d)
+ cd $tmp
+ mkdir -p a/b/c
+ chmod -r a
+
+ cd a
+ # CHECKERR: Unable to open the current working directory: Permission denied
+ pwd
+ # CHECK: {{.*}}/a
+
+ cd b
+ pwd
+ ls
+ # CHECK: {{.*}}/a/b
+ # CHECK: c
+
+ cd $oldpwd
+ chmod -R +rx $tmp # we must be able to list the directory to delete its children
+ rm -rf $tmp
+end