virtio-devices: seccomp: Add seccomp filters for balloon thread

This patch enables the seccomp filters for the balloon worker thread.

Partially fixes: #925

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

virtio-devices/src/balloon.rs

@@ -16,9 +16,11 @@ use super::{
     ActivateError, ActivateResult, EpollHelper, EpollHelperError, EpollHelperHandler, Queue,
     VirtioDevice, VirtioDeviceType, EPOLL_HELPER_EVENT_LAST, VIRTIO_F_VERSION_1,
 };
+use crate::seccomp_filters::{get_seccomp_filter, Thread};
 use crate::vm_memory::GuestMemory;
 use crate::{VirtioInterrupt, VirtioInterruptType};
 use libc::EFD_NONBLOCK;
+use seccomp::{SeccompAction, SeccompFilter};
 use std::io;
 use std::mem::size_of;
 use std::os::unix::io::AsRawFd;
@@ -318,11 +320,12 @@ pub struct Balloon {
     epoll_threads: Option<Vec<thread::JoinHandle<()>>>,
     paused: Arc<AtomicBool>,
     paused_sync: Arc<Barrier>,
+    seccomp_action: SeccompAction,
 }
 
 impl Balloon {
     // Create a new virtio-balloon.
-    pub fn new(id: String, size: u64) -> io::Result<Self> {
+    pub fn new(id: String, size: u64, seccomp_action: SeccompAction) -> io::Result<Self> {
         let avail_features = 1u64 << VIRTIO_F_VERSION_1;
 
         let mut config = VirtioBalloonConfig::default();
@@ -341,6 +344,7 @@ impl Balloon {
             epoll_threads: None,
             paused: Arc::new(AtomicBool::new(false)),
             paused_sync: Arc::new(Barrier::new(2)),
+            seccomp_action,
         })
     }
 
@@ -451,10 +455,15 @@ impl VirtioDevice for Balloon {
         let paused = self.paused.clone();
         let paused_sync = self.paused_sync.clone();
         let mut epoll_threads = Vec::new();
+        let virtio_balloon_seccomp_filter =
+            get_seccomp_filter(&self.seccomp_action, Thread::VirtioBalloon)
+                .map_err(ActivateError::CreateSeccompFilter)?;
         thread::Builder::new()
             .name("virtio_balloon".to_string())
             .spawn(move || {
-                if let Err(e) = handler.run(paused, paused_sync) {
+                if let Err(e) = SeccompFilter::apply(virtio_balloon_seccomp_filter) {
+                    error!("Error applying seccomp filter: {:?}", e);
+                } else if let Err(e) = handler.run(paused, paused_sync) {
                     error!("Error running worker: {:?}", e);
                 }
             })