panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x50 pc=0x71e466]

goroutine 255 [running]:
panic({0xfa2740, 0x1c741b0})
	GOROOT/src/runtime/panic.go:941 +0x397 fp=0xc0004f94e8 sp=0xc0004f9428 pc=0x435a77
runtime.panicmem(...)
	GOROOT/src/runtime/panic.go:220
runtime.sigpanic()
	GOROOT/src/runtime/signal_unix.go:818 +0x336 fp=0xc0004f9538 sp=0xc0004f94e8 pc=0x44c536
gvisor.dev/gvisor/pkg/sentry/vfs.(*VirtualFilesystem).UmountAt(0xc0001b13e8, {0x13613f0, 0xc0006f8a80}, 0xc000879c00?, 0xc00545bb00?, 0xc0004f9794)
	pkg/sentry/vfs/mount.go:657 +0x366 fp=0xc0004f9708 sp=0xc0004f9538 pc=0x71e466
gvisor.dev/gvisor/pkg/sentry/syscalls/linux/vfs2.Umount2(0xc0006f8a80, {{0x7fa625e0a580}, {0xa}, {0x7fa625e0a58c}, {0x56430186e7a3}, {0xffffffff}, {0x7fa625e0a350}})
	pkg/sentry/syscalls/linux/vfs2/mount.go:171 +0x2be fp=0xc0004f98a0 sp=0xc0004f9708 pc=0xbea8fe
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0xc0006f8a80, 0xa6, {{0x7fa625e0a580}, {0xa}, {0x7fa625e0a58c}, {0x56430186e7a3}, {0xffffffff}, {0x7fa625e0a350}})
	pkg/sentry/kernel/task_syscall.go:142 +0x755 fp=0xc0004f9c90 sp=0xc0004f98a0 pc=0x96fff5
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0xc0006f8a80, 0xc00019e2b8?, {{0x7fa625e0a580}, {0xa}, {0x7fa625e0a58c}, {0x56430186e7a3}, {0xffffffff}, {0x7fa625e0a350}})
	pkg/sentry/kernel/task_syscall.go:322 +0x4a fp=0xc0004f9cf0 sp=0xc0004f9c90 pc=0x97122a
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0x0?, 0xc0003a0700?, {{0x7fa625e0a580}, {0xa}, {0x7fa625e0a58c}, {0x56430186e7a3}, {0xffffffff}, {0x7fa625e0a350}})
	pkg/sentry/kernel/task_syscall.go:282 +0x65 fp=0xc0004f9d50 sp=0xc0004f9cf0 pc=0x970f05
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0xc0008acc30?)
	pkg/sentry/kernel/task_syscall.go:257 +0x2f0 fp=0xc0004f9e48 sp=0xc0004f9d50 pc=0x970c70
gvisor.dev/gvisor/pkg/sentry/kernel.(*runApp).execute(0xc0006f8a80?, 0xc0006f8a80)
	pkg/sentry/kernel/task_run.go:253 +0xdea fp=0xc0004f9f60 sp=0xc0004f9e48 pc=0x96520a
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).run(0xc0006f8a80, 0x38)
	pkg/sentry/kernel/task_run.go:94 +0x1ac fp=0xc0004f9fc0 sp=0xc0004f9f60 pc=0x963e0c
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start.func1()
	pkg/sentry/kernel/task_start.go:378 +0x2a fp=0xc0004f9fe0 sp=0xc0004f9fc0 pc=0x96e84a
runtime.goexit()
	src/runtime/asm_amd64.s:1571 +0x1 fp=0xc0004f9fe8 sp=0xc0004f9fe0 pc=0x469781
created by gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start
	pkg/sentry/kernel/task_start.go:378 +0xf9