agent: fix the issue of missing restore process's cwd

It should restore to it's previous cwd after it
create container in which it would change it's
cwd to container's bundle path.

Fixes: #126

Signed-off-by: fupan.lfp <fupan.lfp@antfin.com>

src/agent/Cargo.toml

@@ -20,6 +20,7 @@ prctl = "1.0.0"
 serde_json = "1.0.39"
 signal-hook = "0.1.9"
 scan_fmt = "0.2.3"
+scopeguard = "1.0.0"
 regex = "1"
 # slog:
 # - Dynamic keys required to allow HashMap keys to be slog::Serialized.

src/agent/src/grpc.rs

@@ -113,7 +113,9 @@ impl agentService {
 
         // write spec to bundle path, hooks might
         // read ocispec
-        setup_bundle(oci)?;
+        let olddir = setup_bundle(oci)?;
+        // restore the cwd for kata-agent process.
+        defer!(unistd::chdir(&olddir).unwrap());
 
         let opts = CreateOpts {
             cgroup_name: "".to_string(),
@@ -1738,7 +1740,7 @@ fn do_copy_file(req: &CopyFileRequest) -> Result<()> {
     Ok(())
 }
 
-fn setup_bundle(gspec: &Spec) -> Result<()> {
+fn setup_bundle(gspec: &Spec) -> Result<PathBuf> {
     if gspec.Root.is_none() {
         return Err(nix::Error::Sys(Errno::EINVAL).into());
     }
@@ -1757,7 +1759,8 @@ fn setup_bundle(gspec: &Spec) -> Result<()> {
     );
     let _ = oci.save(config.as_str());
 
+    let olddir = unistd::getcwd().chain_err(|| "cannot getcwd")?;
     unistd::chdir(bundle_path)?;
 
-    Ok(())
+    Ok(olddir)
 }

src/agent/src/main.rs

@@ -20,6 +20,9 @@ extern crate signal_hook;
 extern crate scan_fmt;
 extern crate oci;
 
+#[macro_use]
+extern crate scopeguard;
+
 #[macro_use]
 extern crate slog;
 extern crate slog_async;