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Auto merge of #50630 - sharkdp:fix-50619, r=sfackler

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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
This commit is contained in:
bors 2018-06-26 03:49:37 +00:00
commit 7d2fa4a4d2
1 changed files with 24 additions and 7 deletions
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31
src/libstd/sys/unix/fs.rs
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@ -59,7 +59,10 @@ struct InnerReadDir {
}
#[derive(Clone)]
pub struct ReadDir(Arc<InnerReadDir>);
pub struct ReadDir {
inner: Arc<InnerReadDir>,
end_of_stream: bool,
}
struct Dir(*mut libc::DIR);
@ -215,7 +218,7 @@ impl fmt::Debug for ReadDir {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
// This will only be called from std::fs::ReadDir, which will add a "ReadDir()" frame.
// Thus the result will be e g 'ReadDir("/home")'
fmt::Debug::fmt(&*self.0.root, f)
fmt::Debug::fmt(&*self.inner.root, f)
}
}
@ -231,7 +234,7 @@ impl Iterator for ReadDir {
// is safe to use in threaded applications and it is generally preferred
// over the readdir_r(3C) function.
super::os::set_errno(0);
let entry_ptr = libc::readdir(self.0.dirp.0);
let entry_ptr = libc::readdir(self.inner.dirp.0);
if entry_ptr.is_null() {
// NULL can mean either the end is reached or an error occurred.
// So we had to clear errno beforehand to check for an error now.
@ -259,6 +262,10 @@ impl Iterator for ReadDir {
#[cfg(not(any(target_os = "solaris", target_os = "fuchsia")))]
fn next(&mut self) -> Option<io::Result<DirEntry>> {
if self.end_of_stream {
return None;
}
unsafe {
let mut ret = DirEntry {
entry: mem::zeroed(),
@ -266,7 +273,14 @@ impl Iterator for ReadDir {
};
let mut entry_ptr = ptr::null_mut();
loop {
if readdir64_r(self.0.dirp.0, &mut ret.entry, &mut entry_ptr) != 0 {
if readdir64_r(self.inner.dirp.0, &mut ret.entry, &mut entry_ptr) != 0 {
if entry_ptr.is_null() {
// We encountered an error (which will be returned in this iteration), but
// we also reached the end of the directory stream. The `end_of_stream`
// flag is enabled to make sure that we return `None` in the next iteration
// (instead of looping forever)
self.end_of_stream = true;
}
return Some(Err(Error::last_os_error()))
}
if entry_ptr.is_null() {
@ -289,7 +303,7 @@ impl Drop for Dir {
impl DirEntry {
pub fn path(&self) -> PathBuf {
self.dir.0.root.join(OsStr::from_bytes(self.name_bytes()))
self.dir.inner.root.join(OsStr::from_bytes(self.name_bytes()))
}
pub fn file_name(&self) -> OsString {
@ -298,7 +312,7 @@ impl DirEntry {
#[cfg(any(target_os = "linux", target_os = "emscripten", target_os = "android"))]
pub fn metadata(&self) -> io::Result<FileAttr> {
let fd = cvt(unsafe {dirfd(self.dir.0.dirp.0)})?;
let fd = cvt(unsafe {dirfd(self.dir.inner.dirp.0)})?;
let mut stat: stat64 = unsafe { mem::zeroed() };
cvt(unsafe {
fstatat64(fd, self.entry.d_name.as_ptr(), &mut stat, libc::AT_SYMLINK_NOFOLLOW)
@ -691,7 +705,10 @@ pub fn readdir(p: &Path) -> io::Result<ReadDir> {
Err(Error::last_os_error())
} else {
let inner = InnerReadDir { dirp: Dir(ptr), root };
Ok(ReadDir(Arc::new(inner)))
Ok(ReadDir{
inner: Arc::new(inner),
end_of_stream: false,
})
}
}
}