Fix socket record leak in VFS2

VFS2 socket record is not removed from the system-wide
socket table when the socket is released, which will lead
to a memory leak. This patch fixes this issue.

Fixes: #3874

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>

pkg/sentry/socket/netstack/netstack_vfs2.go

@@ -79,6 +79,13 @@ func NewVFS2(t *kernel.Task, family int, skType linux.SockType, protocol int, qu
 	return vfsfd, nil
 }
 
+// Release implements vfs.FileDescriptionImpl.Release.
+func (s *SocketVFS2) Release(ctx context.Context) {
+	t := kernel.TaskFromContext(ctx)
+	t.Kernel().DeleteSocketVFS2(&s.vfsfd)
+	s.socketOpsCommon.Release(ctx)
+}
+
 // Readiness implements waiter.Waitable.Readiness.
 func (s *SocketVFS2) Readiness(mask waiter.EventMask) waiter.EventMask {
 	return s.socketOpsCommon.Readiness(mask)