Fix possibly endless loop in ReadDir iterator
Certain directories in `/proc` can cause the `ReadDir` iterator to loop indefinitely. We get an error code (22) when calling libc's `readdir_r` on these directories, but `entry_ptr` is `NULL` at the same time, signalling the end of the directory stream. This change introduces an internal state to the iterator such that the `Some(Err(..))` value will only be returned once when calling `next`. Subsequent calls will return `None`. fixes #50619
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@ -57,7 +57,10 @@ struct InnerReadDir {
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}
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#[derive(Clone)]
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pub struct ReadDir(Arc<InnerReadDir>);
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pub struct ReadDir {
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inner: Arc<InnerReadDir>,
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end_of_stream: bool,
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}
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struct Dir(*mut libc::DIR);
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@ -213,7 +216,7 @@ impl fmt::Debug for ReadDir {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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// This will only be called from std::fs::ReadDir, which will add a "ReadDir()" frame.
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// Thus the result will be e g 'ReadDir("/home")'
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fmt::Debug::fmt(&*self.0.root, f)
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fmt::Debug::fmt(&*self.inner.root, f)
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}
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}
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@ -229,7 +232,7 @@ impl Iterator for ReadDir {
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// is safe to use in threaded applications and it is generally preferred
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// over the readdir_r(3C) function.
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super::os::set_errno(0);
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let entry_ptr = libc::readdir(self.0.dirp.0);
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let entry_ptr = libc::readdir(self.inner.dirp.0);
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if entry_ptr.is_null() {
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// NULL can mean either the end is reached or an error occurred.
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// So we had to clear errno beforehand to check for an error now.
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@ -257,6 +260,10 @@ impl Iterator for ReadDir {
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#[cfg(not(any(target_os = "solaris", target_os = "fuchsia")))]
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fn next(&mut self) -> Option<io::Result<DirEntry>> {
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if self.end_of_stream {
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return None;
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}
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unsafe {
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let mut ret = DirEntry {
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entry: mem::zeroed(),
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@ -264,7 +271,14 @@ impl Iterator for ReadDir {
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};
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let mut entry_ptr = ptr::null_mut();
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loop {
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if readdir64_r(self.0.dirp.0, &mut ret.entry, &mut entry_ptr) != 0 {
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if readdir64_r(self.inner.dirp.0, &mut ret.entry, &mut entry_ptr) != 0 {
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if entry_ptr.is_null() {
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// We encountered an error (which will be returned in this iteration), but
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// we also reached the end of the directory stream. The `end_of_stream`
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// flag is enabled to make sure that we return `None` in the next iteration
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// (instead of looping forever)
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self.end_of_stream = true;
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}
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return Some(Err(Error::last_os_error()))
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}
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if entry_ptr.is_null() {
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@ -287,7 +301,7 @@ impl Drop for Dir {
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impl DirEntry {
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pub fn path(&self) -> PathBuf {
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self.dir.0.root.join(OsStr::from_bytes(self.name_bytes()))
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self.dir.inner.root.join(OsStr::from_bytes(self.name_bytes()))
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}
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pub fn file_name(&self) -> OsString {
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@ -296,7 +310,7 @@ impl DirEntry {
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#[cfg(any(target_os = "linux", target_os = "emscripten", target_os = "android"))]
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pub fn metadata(&self) -> io::Result<FileAttr> {
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let fd = cvt(unsafe {dirfd(self.dir.0.dirp.0)})?;
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let fd = cvt(unsafe {dirfd(self.dir.inner.dirp.0)})?;
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let mut stat: stat64 = unsafe { mem::zeroed() };
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cvt(unsafe {
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fstatat(fd,
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@ -692,7 +706,10 @@ pub fn readdir(p: &Path) -> io::Result<ReadDir> {
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Err(Error::last_os_error())
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} else {
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let inner = InnerReadDir { dirp: Dir(ptr), root };
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Ok(ReadDir(Arc::new(inner)))
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Ok(ReadDir{
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inner: Arc::new(inner),
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end_of_stream: false,
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})
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}
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}
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}
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