vhost_user_backend, vmm: Close leaked file descriptors

Explicit call to 'close()' is required on file descriptors allocated
from 'epoll::create()', which is missing for the 'EpollContext' and
'VringWorker'. This patch enforces to close the file descriptors by
reusing the Drop trait of the 'File' struct.

Signed-off-by: Bo Chen <chen.bo@intel.com>

vhost_user_backend/src/lib.rs

@@ -333,7 +333,7 @@ enum VringWorkerError {
 type VringWorkerResult<T> = std::result::Result<T, VringWorkerError>;
 
 pub struct VringWorker {
-    epoll_fd: RawFd,
+    epoll_file: File,
 }
 
 impl VringWorker {
@@ -342,7 +342,7 @@ impl VringWorker {
         let mut events = vec![epoll::Event::new(epoll::Events::empty(), 0); EPOLL_EVENTS_LEN];
 
         'epoll: loop {
-            let num_events = match epoll::wait(self.epoll_fd, -1, &mut events[..]) {
+            let num_events = match epoll::wait(self.epoll_file.as_raw_fd(), -1, &mut events[..]) {
                 Ok(res) => res,
                 Err(e) => {
                     if e.kind() == io::ErrorKind::Interrupted {
@@ -396,7 +396,7 @@ impl VringWorker {
         data: u64,
     ) -> result::Result<(), io::Error> {
         epoll::ctl(
-            self.epoll_fd,
+            self.epoll_file.as_raw_fd(),
             epoll::ControlOptions::EPOLL_CTL_ADD,
             fd,
             epoll::Event::new(ev_type, data),
@@ -413,7 +413,7 @@ impl VringWorker {
         data: u64,
     ) -> result::Result<(), io::Error> {
         epoll::ctl(
-            self.epoll_fd,
+            self.epoll_file.as_raw_fd(),
             epoll::ControlOptions::EPOLL_CTL_DEL,
             fd,
             epoll::Event::new(ev_type, data),
@@ -486,8 +486,10 @@ impl<S: VhostUserBackend> VhostUserHandler<S> {
         for (thread_id, queues_mask) in queues_per_thread.iter().enumerate() {
             // Create the epoll file descriptor
             let epoll_fd = epoll::create(true).map_err(VhostUserHandlerError::EpollCreateFd)?;
+            // Use 'File' to enforce closing on 'epoll_fd'
+            let epoll_file = unsafe { File::from_raw_fd(epoll_fd) };
 
-            let vring_worker = Arc::new(VringWorker { epoll_fd });
+            let vring_worker = Arc::new(VringWorker { epoll_file });
             let worker = vring_worker.clone();
 
             let exit_event_id = if let Some((exit_event_fd, exit_event_id)) =

vmm/src/lib.rs

@@ -29,8 +29,9 @@ use crate::seccomp_filters::{get_seccomp_filter, Thread};
 use crate::vm::{Error as VmError, Vm, VmState};
 use libc::EFD_NONBLOCK;
 use seccomp::{SeccompFilter, SeccompLevel};
+use std::fs::File;
 use std::io;
-use std::os::unix::io::{AsRawFd, RawFd};
+use std::os::unix::io::{AsRawFd, FromRawFd, RawFd};
 use std::path::PathBuf;
 use std::sync::mpsc::{Receiver, RecvError, SendError, Sender};
 use std::sync::{Arc, Mutex};
@@ -115,13 +116,15 @@ pub enum EpollDispatch {
 }
 
 pub struct EpollContext {
-    raw_fd: RawFd,
+    epoll_file: File,
     dispatch_table: Vec<Option<EpollDispatch>>,
 }
 
 impl EpollContext {
     pub fn new() -> result::Result<EpollContext, io::Error> {
-        let raw_fd = epoll::create(true)?;
+        let epoll_fd = epoll::create(true)?;
+        // Use 'File' to enforce closing on 'epoll_fd'
+        let epoll_file = unsafe { File::from_raw_fd(epoll_fd) };
 
         // Initial capacity needs to be large enough to hold:
         // * 1 exit event
@@ -132,7 +135,7 @@ impl EpollContext {
         dispatch_table.push(None);
 
         Ok(EpollContext {
-            raw_fd,
+            epoll_file,
             dispatch_table,
         })
     }
@@ -140,7 +143,7 @@ impl EpollContext {
     pub fn add_stdin(&mut self) -> result::Result<(), io::Error> {
         let dispatch_index = self.dispatch_table.len() as u64;
         epoll::ctl(
-            self.raw_fd,
+            self.epoll_file.as_raw_fd(),
             epoll::ControlOptions::EPOLL_CTL_ADD,
             libc::STDIN_FILENO,
             epoll::Event::new(epoll::Events::EPOLLIN, dispatch_index),
@@ -157,7 +160,7 @@ impl EpollContext {
     {
         let dispatch_index = self.dispatch_table.len() as u64;
         epoll::ctl(
-            self.raw_fd,
+            self.epoll_file.as_raw_fd(),
             epoll::ControlOptions::EPOLL_CTL_ADD,
             fd.as_raw_fd(),
             epoll::Event::new(epoll::Events::EPOLLIN, dispatch_index),
@@ -170,7 +173,7 @@ impl EpollContext {
 
 impl AsRawFd for EpollContext {
     fn as_raw_fd(&self) -> RawFd {
-        self.raw_fd
+        self.epoll_file.as_raw_fd()
     }
 }