runtime: Fix virtiofs fd leak

The kata runtime invokes removeStaleVirtiofsShareMounts after
a container is stopped to clean up the stale virtiofs file caches.

Fixes: #6455
Signed-off-by: Feng Wang <fwang@confluent.io>

src/agent/rustjail/src/mount.rs

@@ -35,7 +35,7 @@ use crate::log_child;
 // struct is populated from the content in the /proc/<pid>/mountinfo file.
 #[derive(std::fmt::Debug, PartialEq)]
 pub struct Info {
-    mount_point: String,
+    pub mount_point: String,
     optional: String,
     fstype: String,
 }
@@ -553,7 +553,7 @@ fn rootfs_parent_mount_private(path: &str) -> Result<()> {
 
 // Parse /proc/self/mountinfo because comparing Dev and ino does not work from
 // bind mounts
-fn parse_mount_table(mountinfo_path: &str) -> Result<Vec<Info>> {
+pub fn parse_mount_table(mountinfo_path: &str) -> Result<Vec<Info>> {
     let file = File::open(mountinfo_path)?;
     let reader = BufReader::new(file);
     let mut infos = Vec::new();

src/agent/src/rpc.rs

@@ -40,6 +40,7 @@ use protocols::types::Interface;
 use protocols::{agent_ttrpc_async as agent_ttrpc, health_ttrpc_async as health_ttrpc};
 use rustjail::cgroups::notifier;
 use rustjail::container::{BaseContainer, Container, LinuxContainer, SYSTEMD_CGROUP_PATH_FORMAT};
+use rustjail::mount::parse_mount_table;
 use rustjail::process::Process;
 use rustjail::specconv::CreateOpts;
 
@@ -96,6 +97,7 @@ const USR_IP6TABLES_SAVE: &str = "/usr/sbin/ip6tables-save";
 const IP6TABLES_SAVE: &str = "/sbin/ip6tables-save";
 const USR_IP6TABLES_RESTORE: &str = "/usr/sbin/ip6tables-save";
 const IP6TABLES_RESTORE: &str = "/sbin/ip6tables-restore";
+const KATA_GUEST_SHARE_DIR: &str = "/run/kata-containers/shared/containers/";
 
 const ERR_CANNOT_GET_WRITER: &str = "Cannot get writer";
 const ERR_INVALID_BLOCK_SIZE: &str = "Invalid block size";
@@ -829,6 +831,29 @@ impl agent_ttrpc::AgentService for AgentService {
         Ok(Empty::new())
     }
 
+    async fn remove_stale_virtiofs_share_mounts(
+        &self,
+        ctx: &TtrpcContext,
+        req: protocols::agent::RemoveStaleVirtiofsShareMountsRequest,
+    ) -> ttrpc::Result<Empty> {
+        trace_rpc_call!(ctx, "remove_stale_virtiofs_share_mounts", req);
+        is_allowed!(req);
+        let mount_infos = parse_mount_table("/proc/self/mountinfo")
+            .map_err(|e| ttrpc_error!(ttrpc::Code::INTERNAL, e))?;
+        for m in &mount_infos {
+            if m.mount_point.starts_with(KATA_GUEST_SHARE_DIR) {
+                // stat the mount point, virtiofs daemon will remove the stale cache and release the fds if the mount point doesn't exist any more.
+                // More details in https://github.com/kata-containers/kata-containers/issues/6455#issuecomment-1477137277
+                match stat::stat(Path::new(&m.mount_point)) {
+                    Ok(_) => info!(sl!(), "stat {} success", m.mount_point),
+                    Err(e) => info!(sl!(), "stat {} failed: {}", m.mount_point, e),
+                }
+            }
+        }
+
+        Ok(Empty::new())
+    }
+
     async fn write_stdin(
         &self,
         _ctx: &TtrpcContext,

src/libs/protocols/protos/agent.proto

@@ -38,6 +38,7 @@ service AgentService {
 	rpc StatsContainer(StatsContainerRequest) returns (StatsContainerResponse);
 	rpc PauseContainer(PauseContainerRequest) returns (google.protobuf.Empty);
 	rpc ResumeContainer(ResumeContainerRequest) returns (google.protobuf.Empty);
+	rpc RemoveStaleVirtiofsShareMounts(RemoveStaleVirtiofsShareMountsRequest) returns (google.protobuf.Empty);
 
 	// stdio
 	rpc WriteStdin(WriteStreamRequest) returns (WriteStreamResponse);
@@ -301,6 +302,8 @@ message CreateSandboxRequest {
 message DestroySandboxRequest {
 }
 
+message RemoveStaleVirtiofsShareMountsRequest {}
+
 message Interfaces {
 	repeated types.Interface Interfaces = 1;
 }

src/runtime/virtcontainers/agent.go

@@ -138,6 +138,9 @@ type agent interface {
 	// resumeContainer will resume a paused container
 	resumeContainer(ctx context.Context, sandbox *Sandbox, c Container) error
 
+	// removeStaleVirtiofsShareMounts will tell the agent to remove stale virtiofs share mounts in the guest.
+	removeStaleVirtiofsShareMounts(ctx context.Context) error
+
 	// configure will update agent settings based on provided arguments
 	configure(ctx context.Context, h Hypervisor, id, sharePath string, config KataAgentConfig) error
 

src/runtime/virtcontainers/container.go

@@ -1020,6 +1020,10 @@ func (c *Container) stop(ctx context.Context, force bool) error {
 		}
 	}
 
+	if err := c.sandbox.agent.removeStaleVirtiofsShareMounts(ctx); err != nil && !force {
+		return err
+	}
+
 	if err := c.detachDevices(ctx); err != nil && !force {
 		return err
 	}

src/runtime/virtcontainers/container_linux_test.go

@@ -125,6 +125,7 @@ func TestUnmountHostMountsRemoveBindHostPath(t *testing.T) {
 		ctx:    context.Background(),
 		id:     "foobar",
 		config: &SandboxConfig{},
+		agent:  newMockAgent(),
 	}
 
 	fsShare, err := NewFilesystemShare(sandbox)

src/runtime/virtcontainers/container_test.go

@@ -302,6 +302,7 @@ func TestMountSharedDirMounts(t *testing.T) {
 	sandbox := &Sandbox{
 		ctx:        context.Background(),
 		id:         "foobar",
+		agent:      newMockAgent(),
 		hypervisor: &mockHypervisor{},
 		config: &SandboxConfig{
 			HypervisorConfig: HypervisorConfig{

src/runtime/virtcontainers/kata_agent.go

@@ -113,41 +113,42 @@ var (
 )
 
 const (
-	grpcCheckRequest                 = "grpc.CheckRequest"
-	grpcExecProcessRequest           = "grpc.ExecProcessRequest"
-	grpcCreateSandboxRequest         = "grpc.CreateSandboxRequest"
-	grpcDestroySandboxRequest        = "grpc.DestroySandboxRequest"
-	grpcCreateContainerRequest       = "grpc.CreateContainerRequest"
-	grpcStartContainerRequest        = "grpc.StartContainerRequest"
-	grpcRemoveContainerRequest       = "grpc.RemoveContainerRequest"
-	grpcSignalProcessRequest         = "grpc.SignalProcessRequest"
-	grpcUpdateRoutesRequest          = "grpc.UpdateRoutesRequest"
-	grpcUpdateInterfaceRequest       = "grpc.UpdateInterfaceRequest"
-	grpcUpdateEphemeralMountsRequest = "grpc.UpdateEphemeralMountsRequest"
-	grpcListInterfacesRequest        = "grpc.ListInterfacesRequest"
-	grpcListRoutesRequest            = "grpc.ListRoutesRequest"
-	grpcAddARPNeighborsRequest       = "grpc.AddARPNeighborsRequest"
-	grpcOnlineCPUMemRequest          = "grpc.OnlineCPUMemRequest"
-	grpcUpdateContainerRequest       = "grpc.UpdateContainerRequest"
-	grpcWaitProcessRequest           = "grpc.WaitProcessRequest"
-	grpcTtyWinResizeRequest          = "grpc.TtyWinResizeRequest"
-	grpcWriteStreamRequest           = "grpc.WriteStreamRequest"
-	grpcCloseStdinRequest            = "grpc.CloseStdinRequest"
-	grpcStatsContainerRequest        = "grpc.StatsContainerRequest"
-	grpcPauseContainerRequest        = "grpc.PauseContainerRequest"
-	grpcResumeContainerRequest       = "grpc.ResumeContainerRequest"
-	grpcReseedRandomDevRequest       = "grpc.ReseedRandomDevRequest"
-	grpcGuestDetailsRequest          = "grpc.GuestDetailsRequest"
-	grpcMemHotplugByProbeRequest     = "grpc.MemHotplugByProbeRequest"
-	grpcCopyFileRequest              = "grpc.CopyFileRequest"
-	grpcSetGuestDateTimeRequest      = "grpc.SetGuestDateTimeRequest"
-	grpcGetOOMEventRequest           = "grpc.GetOOMEventRequest"
-	grpcGetMetricsRequest            = "grpc.GetMetricsRequest"
-	grpcAddSwapRequest               = "grpc.AddSwapRequest"
-	grpcVolumeStatsRequest           = "grpc.VolumeStatsRequest"
-	grpcResizeVolumeRequest          = "grpc.ResizeVolumeRequest"
-	grpcGetIPTablesRequest           = "grpc.GetIPTablesRequest"
-	grpcSetIPTablesRequest           = "grpc.SetIPTablesRequest"
+	grpcCheckRequest                          = "grpc.CheckRequest"
+	grpcExecProcessRequest                    = "grpc.ExecProcessRequest"
+	grpcCreateSandboxRequest                  = "grpc.CreateSandboxRequest"
+	grpcDestroySandboxRequest                 = "grpc.DestroySandboxRequest"
+	grpcCreateContainerRequest                = "grpc.CreateContainerRequest"
+	grpcStartContainerRequest                 = "grpc.StartContainerRequest"
+	grpcRemoveContainerRequest                = "grpc.RemoveContainerRequest"
+	grpcSignalProcessRequest                  = "grpc.SignalProcessRequest"
+	grpcUpdateRoutesRequest                   = "grpc.UpdateRoutesRequest"
+	grpcUpdateInterfaceRequest                = "grpc.UpdateInterfaceRequest"
+	grpcUpdateEphemeralMountsRequest          = "grpc.UpdateEphemeralMountsRequest"
+	grpcRemoveStaleVirtiofsShareMountsRequest = "grpc.RemoveStaleVirtiofsShareMountsRequest"
+	grpcListInterfacesRequest                 = "grpc.ListInterfacesRequest"
+	grpcListRoutesRequest                     = "grpc.ListRoutesRequest"
+	grpcAddARPNeighborsRequest                = "grpc.AddARPNeighborsRequest"
+	grpcOnlineCPUMemRequest                   = "grpc.OnlineCPUMemRequest"
+	grpcUpdateContainerRequest                = "grpc.UpdateContainerRequest"
+	grpcWaitProcessRequest                    = "grpc.WaitProcessRequest"
+	grpcTtyWinResizeRequest                   = "grpc.TtyWinResizeRequest"
+	grpcWriteStreamRequest                    = "grpc.WriteStreamRequest"
+	grpcCloseStdinRequest                     = "grpc.CloseStdinRequest"
+	grpcStatsContainerRequest                 = "grpc.StatsContainerRequest"
+	grpcPauseContainerRequest                 = "grpc.PauseContainerRequest"
+	grpcResumeContainerRequest                = "grpc.ResumeContainerRequest"
+	grpcReseedRandomDevRequest                = "grpc.ReseedRandomDevRequest"
+	grpcGuestDetailsRequest                   = "grpc.GuestDetailsRequest"
+	grpcMemHotplugByProbeRequest              = "grpc.MemHotplugByProbeRequest"
+	grpcCopyFileRequest                       = "grpc.CopyFileRequest"
+	grpcSetGuestDateTimeRequest               = "grpc.SetGuestDateTimeRequest"
+	grpcGetOOMEventRequest                    = "grpc.GetOOMEventRequest"
+	grpcGetMetricsRequest                     = "grpc.GetMetricsRequest"
+	grpcAddSwapRequest                        = "grpc.AddSwapRequest"
+	grpcVolumeStatsRequest                    = "grpc.VolumeStatsRequest"
+	grpcResizeVolumeRequest                   = "grpc.ResizeVolumeRequest"
+	grpcGetIPTablesRequest                    = "grpc.GetIPTablesRequest"
+	grpcSetIPTablesRequest                    = "grpc.SetIPTablesRequest"
 )
 
 // newKataAgent returns an agent from an agent type.
@@ -1947,6 +1948,11 @@ func (k *kataAgent) reseedRNG(ctx context.Context, data []byte) error {
 	return err
 }
 
+func (k *kataAgent) removeStaleVirtiofsShareMounts(ctx context.Context) error {
+	_, err := k.sendReq(ctx, &grpc.RemoveStaleVirtiofsShareMountsRequest{})
+	return err
+}
+
 type reqFunc func(context.Context, interface{}) (interface{}, error)
 
 func (k *kataAgent) installReqFunc(c *kataclient.AgentClient) {
@@ -2056,6 +2062,9 @@ func (k *kataAgent) installReqFunc(c *kataclient.AgentClient) {
 	k.reqHandlers[grpcSetIPTablesRequest] = func(ctx context.Context, req interface{}) (interface{}, error) {
 		return k.client.AgentServiceClient.SetIPTables(ctx, req.(*grpc.SetIPTablesRequest))
 	}
+	k.reqHandlers[grpcRemoveStaleVirtiofsShareMountsRequest] = func(ctx context.Context, req interface{}) (interface{}, error) {
+		return k.client.AgentServiceClient.RemoveStaleVirtiofsShareMounts(ctx, req.(*grpc.RemoveStaleVirtiofsShareMountsRequest))
+	}
 }
 
 func (k *kataAgent) getReqContext(ctx context.Context, reqName string) (newCtx context.Context, cancel context.CancelFunc) {

src/runtime/virtcontainers/kata_agent_test.go

@@ -846,6 +846,7 @@ func TestAgentCreateContainer(t *testing.T) {
 			},
 		},
 		hypervisor: &mockHypervisor{},
+		agent:      newMockAgent(),
 	}
 
 	fsShare, err := NewFilesystemShare(sandbox)

src/runtime/virtcontainers/mock_agent.go

@@ -141,6 +141,11 @@ func (n *mockAgent) waitProcess(ctx context.Context, c *Container, processID str
 	return 0, nil
 }
 
+// removeStaleVirtiofsShareMounts is the Noop agent removeStaleVirtiofsShareMounts implementation. It does nothing.
+func (n *mockAgent) removeStaleVirtiofsShareMounts(ctx context.Context) error {
+	return nil
+}
+
 // winsizeProcess is the Noop agent process tty resizer. It does nothing.
 func (n *mockAgent) winsizeProcess(ctx context.Context, c *Container, processID string, height, width uint32) error {
 	return nil

src/runtime/virtcontainers/pkg/mock/mock.go

@@ -245,6 +245,10 @@ func (p *HybridVSockTTRPCMockImp) ResizeVolume(ctx context.Context, req *pb.Resi
 	return &gpb.Empty{}, nil
 }
 
+func (p *HybridVSockTTRPCMockImp) RemoveStaleVirtiofsShareMounts(ctx context.Context, req *pb.RemoveStaleVirtiofsShareMountsRequest) (*gpb.Empty, error) {
+	return &gpb.Empty{}, nil
+}
+
 func (p *HybridVSockTTRPCMockImp) GetIPTables(ctx context.Context, req *pb.GetIPTablesRequest) (*pb.GetIPTablesResponse, error) {
 	return &pb.GetIPTablesResponse{}, nil
 }