panic: kernfs.Dentry.DecRef() called without holding a reference

goroutine 12355 [running]:
panic(0x10cb560, 0x14321c8)
	GOROOT/src/runtime/panic.go:1065 +0x565 fp=0xc000bd9798 sp=0xc000bd96d0 pc=0x437c65
gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs.(*Dentry).DecRef(0xc0007c0b40, 0x1476d00, 0xc000a77500)
	pkg/sentry/fsimpl/kernfs/kernfs.go:283 +0xb2 fp=0xc000bd97c0 sp=0xc000bd9798 pc=0x852d52
gvisor.dev/gvisor/pkg/sentry/vfs.(*Dentry).DecRef(...)
	pkg/sentry/vfs/dentry.go:157
gvisor.dev/gvisor/pkg/sentry/vfs.VirtualDentry.DecRef(0xc00032ade0, 0xc0007c0b40, 0x1476d00, 0xc000a77500)
	pkg/sentry/vfs/vfs.go:928 +0x49 fp=0xc000bd97e8 sp=0xc000bd97c0 pc=0x75f429
gvisor.dev/gvisor/pkg/sentry/vfs.(*VirtualFilesystem).UmountAt(0xc000498178, 0x1476d00, 0xc000a77500, 0xc000760ba0, 0xc000bd9a38, 0xc000bd9a1c, 0x0, 0x0)
	pkg/sentry/vfs/mount.go:354 +0x4c0 fp=0xc000bd9980 sp=0xc000bd97e8 pc=0x752060
gvisor.dev/gvisor/pkg/sentry/syscalls/linux/vfs2.Umount2(0xc000a77500, 0x7fa30b2f7580, 0x2, 0x7fa30b2f758c, 0x55f3ed131b93, 0xffffffff, 0x7fa30b2f7350, 0x0, 0x0, 0x0, ...)
	pkg/sentry/syscalls/linux/vfs2/mount.go:149 +0x335 fp=0xc000bd9b00 sp=0xc000bd9980 pc=0xe3aaf5
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0xc000a77500, 0xa6, 0x7fa30b2f7580, 0x2, 0x7fa30b2f758c, 0x55f3ed131b93, 0xffffffff, 0x7fa30b2f7350, 0x0, 0x12d7840, ...)
	pkg/sentry/kernel/task_syscall.go:103 +0x13c fp=0xc000bd9c60 sp=0xc000bd9b00 pc=0x9d7cfc
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0xc000a77500, 0xa6, 0x7fa30b2f7580, 0x2, 0x7fa30b2f758c, 0x55f3ed131b93, 0xffffffff, 0x7fa30b2f7350, 0xffffffff, 0x7fa30b2f7350)
	pkg/sentry/kernel/task_syscall.go:238 +0x66 fp=0xc000bd9ce8 sp=0xc000bd9c60 pc=0x9d8e86
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0xc000a77500, 0xa6, 0x7fa30b2f7580, 0x2, 0x7fa30b2f758c, 0x55f3ed131b93, 0xffffffff, 0x7fa30b2f7350, 0xc0003fb2a0, 0xc0003fb200)
	pkg/sentry/kernel/task_syscall.go:198 +0x98 fp=0xc000bd9d48 sp=0xc000bd9ce8 pc=0x9d8a78
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0xc000a77500, 0x2, 0xc000a77500)
	pkg/sentry/kernel/task_syscall.go:173 +0x15c fp=0xc000bd9e18 sp=0xc000bd9d48 pc=0x9d841c
gvisor.dev/gvisor/pkg/sentry/kernel.(*runApp).execute(0x0, 0xc000a77500, 0x144a920, 0x0)
	pkg/sentry/kernel/task_run.go:282 +0xc8c fp=0xc000bd9f60 sp=0xc000bd9e18 pc=0x9cd0ac
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).run(0xc000a77500, 0x2a)
	pkg/sentry/kernel/task_run.go:97 +0x1af fp=0xc000bd9fd0 sp=0xc000bd9f60 pc=0x9cbd2f
runtime.goexit()
	src/runtime/asm_amd64.s:1371 +0x1 fp=0xc000bd9fd8 sp=0xc000bd9fd0 pc=0x472861
created by gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start
	pkg/sentry/kernel/task_start.go:327 +0xfe