runtime-rs: add parameter for propagation of (u)mount events

Add an extra parameter in `bind_mount_unchecked` to specify
the propagation type: "shared" or "slave".

Fixes: #7017

Signed-off-by: Anastassios Nanos <ananos@nubificus.co.uk>

src/libs/kata-sys-util/src/mount.rs

@@ -103,6 +103,8 @@ pub enum Error {
     MountOptionTooBig,
     #[error("Path for mountpoint is null")]
     NullMountPointPath,
+    #[error("Invalid Propagation type Flag")]
+    InvalidPgMountFlag,
     #[error("Faile to open file {0} by path, {1}")]
     OpenByPath(PathBuf, io::Error),
     #[error("Can not read metadata of {0}, {1}")]
@@ -227,7 +229,13 @@ pub fn bind_remount<P: AsRef<Path>>(dst: P, readonly: bool) -> Result<()> {
     do_rebind_mount(dst, readonly, MsFlags::empty())
 }
 
-/// Bind mount `src` to `dst` in slave mode, optionally in readonly mode if `readonly` is true.
+/// Bind mount `src` to `dst` with a custom propagation type, optionally in readonly mode if
+/// `readonly` is true.
+///
+/// Propagation type: MsFlags::MS_SHARED or MsFlags::MS_SLAVE
+/// MsFlags::MS_SHARED is used to bind mount the sandbox path to enable `exec` (in case of FC
+/// jailer).
+/// MsFlags::MS_SLAVE is used on all other cases.
 ///
 /// # Safety
 /// Caller needs to ensure:
@@ -238,6 +246,7 @@ pub fn bind_mount_unchecked<S: AsRef<Path>, D: AsRef<Path>>(
     src: S,
     dst: D,
     readonly: bool,
+    pgflag: MsFlags,
 ) -> Result<()> {
     fail::fail_point!("bind_mount", |_| {
         Err(Error::FailureInject(
@@ -268,8 +277,11 @@ pub fn bind_mount_unchecked<S: AsRef<Path>, D: AsRef<Path>>(
     )
     .map_err(|e| Error::BindMount(abs_src, dst.to_path_buf(), e))?;
 
-    // Change into slave propagation mode.
-    mount(Some(""), dst, Some(""), MsFlags::MS_SLAVE, Some(""))
+    // Change into the chosen propagation mode.
+    if !(pgflag == MsFlags::MS_SHARED || pgflag == MsFlags::MS_SLAVE) {
+        return Err(Error::InvalidPgMountFlag);
+    }
+    mount(Some(""), dst, Some(""), pgflag, Some(""))
         .map_err(|e| Error::Mount(PathBuf::new(), dst.to_path_buf(), e))?;
 
     // Optionally rebind into readonly mode.
@@ -828,7 +840,7 @@ mod tests {
             Err(Error::InvalidPath(_))
         ));
 
-        bind_mount_unchecked(tmpdir2.path(), tmpdir.path(), true).unwrap();
+        bind_mount_unchecked(tmpdir2.path(), tmpdir.path(), true, MsFlags::MS_SLAVE).unwrap();
         bind_remount(tmpdir.path(), true).unwrap();
         umount_timeout(tmpdir.path().to_str().unwrap(), 0).unwrap();
     }
@@ -844,25 +856,26 @@ mod tests {
         dst.push("src");
 
         assert!(matches!(
-            bind_mount_unchecked(Path::new(""), Path::new(""), false),
+            bind_mount_unchecked(Path::new(""), Path::new(""), false, MsFlags::MS_SLAVE),
             Err(Error::NullMountPointPath)
         ));
         assert!(matches!(
-            bind_mount_unchecked(tmpdir2.path(), Path::new(""), false),
+            bind_mount_unchecked(tmpdir2.path(), Path::new(""), false, MsFlags::MS_SLAVE),
             Err(Error::NullMountPointPath)
         ));
         assert!(matches!(
             bind_mount_unchecked(
                 Path::new("/_does_not_exist_/___aahhhh"),
                 Path::new("/tmp/_does_not_exist/___bbb"),
-                false
+                false,
+                MsFlags::MS_SLAVE
             ),
             Err(Error::InvalidPath(_))
         ));
 
         let dst = create_mount_destination(tmpdir2.path(), &dst, tmpdir.path(), "bind").unwrap();
-        bind_mount_unchecked(tmpdir2.path(), dst.as_ref(), true).unwrap();
-        bind_mount_unchecked(&src, dst.as_ref(), false).unwrap();
+        bind_mount_unchecked(tmpdir2.path(), dst.as_ref(), true, MsFlags::MS_SLAVE).unwrap();
+        bind_mount_unchecked(&src, dst.as_ref(), false, MsFlags::MS_SLAVE).unwrap();
         umount_all(dst.as_ref(), false).unwrap();
 
         let mut src = tmpdir.path().to_owned();
@@ -871,7 +884,7 @@ mod tests {
         let mut dst = tmpdir.path().to_owned();
         dst.push("file");
         let dst = create_mount_destination(&src, &dst, tmpdir.path(), "bind").unwrap();
-        bind_mount_unchecked(&src, dst.as_ref(), false).unwrap();
+        bind_mount_unchecked(&src, dst.as_ref(), false, MsFlags::MS_SLAVE).unwrap();
         assert!(dst.as_ref().is_file());
         umount_timeout(dst.as_ref(), 0).unwrap();
     }

src/runtime-rs/crates/hypervisor/src/dragonball/inner.rs

@@ -16,11 +16,13 @@ use dragonball::{
     api::v1::{BlockDeviceConfigInfo, BootSourceConfig, VcpuResizeInfo},
     vm::VmConfigInfo,
 };
+
 use kata_sys_util::mount;
 use kata_types::{
     capabilities::{Capabilities, CapabilityBits},
     config::hypervisor::Hypervisor as HypervisorConfig,
 };
+use nix::mount::MsFlags;
 use persist::sandbox_persist::Persist;
 use shim_interface::KATA_PATH;
 use std::{collections::HashSet, fs::create_dir_all, path::PathBuf};
@@ -232,7 +234,8 @@ impl DragonballInner {
         }
 
         let jailed_location = [self.jailer_root.as_str(), dst].join("/");
-        mount::bind_mount_unchecked(src, jailed_location.as_str(), false).context("bind_mount")?;
+        mount::bind_mount_unchecked(src, jailed_location.as_str(), false, MsFlags::MS_SLAVE)
+            .context("bind_mount")?;
 
         let mut abs_path = String::from("/");
         abs_path.push_str(dst);

src/runtime-rs/crates/resource/src/share_fs/sandbox_bind_mounts.rs

@@ -23,6 +23,7 @@ use anyhow::{anyhow, Context, Result};
 use super::utils::{do_get_host_path, mkdir_with_permissions};
 use kata_sys_util::{fs::get_base_name, mount};
 use kata_types::mount::{SANDBOX_BIND_MOUNTS_DIR, SANDBOX_BIND_MOUNTS_RO, SANDBOX_BIND_MOUNTS_RW};
+use nix::mount::MsFlags;
 
 #[derive(Clone, Default, Debug)]
 pub struct SandboxBindMounts {
@@ -101,7 +102,8 @@ impl SandboxBindMounts {
 
             // mount -o bind,ro host_shared mount_dest
             // host_shared: ${bindmount}
-            mount::bind_mount_unchecked(Path::new(bindmount), &mount_dest, true).map_err(|e| {
+            mount::bind_mount_unchecked(Path::new(bindmount), &mount_dest, true, MsFlags::MS_SLAVE)
+                .map_err(|e| {
                     for p in &mounted_list {
                         nix::mount::umount(p).unwrap_or_else(|x| {
                             format!("do umount failed: {:?}", x);

src/runtime-rs/crates/resource/src/share_fs/share_virtio_fs.rs

@@ -18,6 +18,7 @@ use hypervisor::{
     Hypervisor, ShareFsDeviceConfig,
 };
 use kata_sys_util::mount;
+use nix::mount::MsFlags;
 
 use super::{utils, PASSTHROUGH_FS_DIR};
 
@@ -45,7 +46,7 @@ pub(crate) async fn prepare_virtiofs(
     let host_rw_dest = utils::get_host_rw_shared_path(id);
     utils::ensure_dir_exist(&host_rw_dest)?;
 
-    mount::bind_mount_unchecked(&host_rw_dest, &host_ro_dest, true)
+    mount::bind_mount_unchecked(&host_rw_dest, &host_ro_dest, true, MsFlags::MS_SLAVE)
         .context("bind mount shared_fs directory")?;
 
     let share_fs_device = ShareFsDevice {

src/runtime-rs/crates/resource/src/share_fs/utils.rs

@@ -11,6 +11,7 @@ use std::{
 
 use anyhow::Result;
 use kata_sys_util::mount;
+use nix::mount::MsFlags;
 
 use super::*;
 
@@ -45,7 +46,7 @@ pub(crate) fn share_to_guest(
     is_rafs: bool,
 ) -> Result<String> {
     let host_dest = do_get_host_path(target, sid, cid, is_volume, false);
-    mount::bind_mount_unchecked(source, &host_dest, readonly)
+    mount::bind_mount_unchecked(source, &host_dest, readonly, MsFlags::MS_SLAVE)
         .with_context(|| format!("failed to bind mount {} to {}", source, &host_dest))?;
 
     // bind mount remount event is not propagated to mount subtrees, so we have