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

goroutine 10503 [running]:
panic(0x10cb560, 0x14321a8)
	GOROOT/src/runtime/panic.go:1065 +0x565 fp=0xc001c2f798 sp=0xc001c2f6d0 pc=0x437c65
gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs.(*Dentry).DecRef(0xc0006ec990, 0x1476ce0, 0xc0004c7500)
	pkg/sentry/fsimpl/kernfs/kernfs.go:283 +0xb2 fp=0xc001c2f7c0 sp=0xc001c2f798 pc=0x852d52
gvisor.dev/gvisor/pkg/sentry/vfs.(*Dentry).DecRef(...)
	pkg/sentry/vfs/dentry.go:157
gvisor.dev/gvisor/pkg/sentry/vfs.VirtualDentry.DecRef(0xc020ee1740, 0xc0006ec990, 0x1476ce0, 0xc0004c7500)
	pkg/sentry/vfs/vfs.go:928 +0x49 fp=0xc001c2f7e8 sp=0xc001c2f7c0 pc=0x75f429
gvisor.dev/gvisor/pkg/sentry/vfs.(*VirtualFilesystem).UmountAt(0xc00034b078, 0x1476ce0, 0xc0004c7500, 0xc000ca4ae0, 0xc001c2fa38, 0xc001c2fa1c, 0x0, 0x0)
	pkg/sentry/vfs/mount.go:354 +0x4c0 fp=0xc001c2f980 sp=0xc001c2f7e8 pc=0x752060
gvisor.dev/gvisor/pkg/sentry/syscalls/linux/vfs2.Umount2(0xc0004c7500, 0x7f7afb18e580, 0x2, 0x7f7afb18e58c, 0x5646b4bdab93, 0xffffffff, 0x7f7afb18e350, 0x0, 0x0, 0x0, ...)
	pkg/sentry/syscalls/linux/vfs2/mount.go:149 +0x335 fp=0xc001c2fb00 sp=0xc001c2f980 pc=0xe3aa95
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0xc0004c7500, 0xa6, 0x7f7afb18e580, 0x2, 0x7f7afb18e58c, 0x5646b4bdab93, 0xffffffff, 0x7f7afb18e350, 0x0, 0x12d7840, ...)
	pkg/sentry/kernel/task_syscall.go:103 +0x13c fp=0xc001c2fc60 sp=0xc001c2fb00 pc=0x9d7cfc
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0xc0004c7500, 0xa6, 0x7f7afb18e580, 0x2, 0x7f7afb18e58c, 0x5646b4bdab93, 0xffffffff, 0x7f7afb18e350, 0xffffffff, 0x7f7afb18e350)
	pkg/sentry/kernel/task_syscall.go:238 +0x66 fp=0xc001c2fce8 sp=0xc001c2fc60 pc=0x9d8e86
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0xc0004c7500, 0xa6, 0x7f7afb18e580, 0x2, 0x7f7afb18e58c, 0x5646b4bdab93, 0xffffffff, 0x7f7afb18e350, 0xc00002c8e0, 0xc00002c840)
	pkg/sentry/kernel/task_syscall.go:198 +0x98 fp=0xc001c2fd48 sp=0xc001c2fce8 pc=0x9d8a78
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0xc0004c7500, 0x2, 0xc0004c7500)
	pkg/sentry/kernel/task_syscall.go:173 +0x15c fp=0xc001c2fe18 sp=0xc001c2fd48 pc=0x9d841c
gvisor.dev/gvisor/pkg/sentry/kernel.(*runApp).execute(0x0, 0xc0004c7500, 0x144a900, 0x0)
	pkg/sentry/kernel/task_run.go:282 +0xc8c fp=0xc001c2ff60 sp=0xc001c2fe18 pc=0x9cd0ac
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).run(0xc0004c7500, 0x3c)
	pkg/sentry/kernel/task_run.go:97 +0x1af fp=0xc001c2ffd0 sp=0xc001c2ff60 pc=0x9cbd2f
runtime.goexit()
	src/runtime/asm_amd64.s:1371 +0x1 fp=0xc001c2ffd8 sp=0xc001c2ffd0 pc=0x472861
created by gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start
	pkg/sentry/kernel/task_start.go:327 +0xfe