panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x50 pc=0x75073e]

goroutine 1248568 [running]:
panic({0x10a9780, 0x1f40f50})
	GOROOT/src/runtime/panic.go:941 +0x397 fp=0xc00691b598 sp=0xc00691b4d8 pc=0x4358b7
runtime.panicmem(...)
	GOROOT/src/runtime/panic.go:220
runtime.sigpanic()
	GOROOT/src/runtime/signal_unix.go:818 +0x336 fp=0xc00691b5e8 sp=0xc00691b598 pc=0x44c376
gvisor.dev/gvisor/pkg/sentry/vfs.(*VirtualFilesystem).UmountAt(0xc00003c4e8, {0x149c1f0, 0xc006812000}, 0xc000181400?, 0xc0078c2200?, 0xc00691b84c)
	pkg/sentry/vfs/mount.go:657 +0x43e fp=0xc00691b7c0 sp=0xc00691b5e8 pc=0x75073e
gvisor.dev/gvisor/pkg/sentry/syscalls/linux/vfs2.Umount2(0xc006812000, {{0x20000080}, {0x2}, {0x0}, {0x0}, {0x0}, {0x0}})
	pkg/sentry/syscalls/linux/vfs2/mount.go:171 +0x326 fp=0xc00691b958 sp=0xc00691b7c0 pc=0xcc3c26
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0xc006812000, 0xa6, {{0x20000080}, {0x2}, {0x0}, {0x0}, {0x0}, {0x0}})
	pkg/sentry/kernel/task_syscall.go:142 +0x80b fp=0xc00691bc98 sp=0xc00691b958 pc=0x9fd60b
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0xc006812000, 0x85?, {{0x20000080}, {0x2}, {0x0}, {0x0}, {0x0}, {0x0}})
	pkg/sentry/kernel/task_syscall.go:322 +0x54 fp=0xc00691bcf8 sp=0xc00691bc98 pc=0x9febf4
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0x891aef?, 0x0?, {{0x20000080}, {0x2}, {0x0}, {0x0}, {0x0}, {0x0}})
	pkg/sentry/kernel/task_syscall.go:282 +0x85 fp=0xc00691bd58 sp=0xc00691bcf8 pc=0x9fe7e5
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0xc0065a9380?)
	pkg/sentry/kernel/task_syscall.go:257 +0x3ac fp=0xc00691be50 sp=0xc00691bd58 pc=0x9fe4ac
gvisor.dev/gvisor/pkg/sentry/kernel.(*runApp).execute(0xc008807500?, 0xc006812000)
	pkg/sentry/kernel/task_run.go:253 +0x1125 fp=0xc00691bf60 sp=0xc00691be50 pc=0x9f03c5
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).run(0xc006812000, 0xa353)
	pkg/sentry/kernel/task_run.go:94 +0x1ec fp=0xc00691bfc0 sp=0xc00691bf60 pc=0x9eec0c
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start.func1()
	pkg/sentry/kernel/task_start.go:378 +0x2a fp=0xc00691bfe0 sp=0xc00691bfc0 pc=0x9fbaaa
runtime.goexit()
	src/runtime/asm_amd64.s:1571 +0x1 fp=0xc00691bfe8 sp=0xc00691bfe0 pc=0x4695c1
created by gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start
	pkg/sentry/kernel/task_start.go:378 +0x105