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

goroutine 6816 [running]:
panic({0xf82ce0, 0x1368f68})
	GOROOT/src/runtime/panic.go:941 +0x397 fp=0xc0089e1198 sp=0xc0089e10d8 pc=0x4358b7
gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs.(*Dentry).decRefLocked(0x967765?, {0x13831b0?, 0xc00251ca80?})
	pkg/sentry/fsimpl/kernfs/kernfs.go:302 +0xac fp=0xc0089e11c0 sp=0xc0089e1198 pc=0x7dc26c
gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs.(*Dentry).releaseKeptDentriesLocked(0xc004865290, {0x13831b0, 0xc00251ca80})
	pkg/sentry/fsimpl/kernfs/filesystem.go:282 +0x98 fp=0xc0089e12a0 sp=0xc0089e11c0 pc=0x7cdb38
gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs.(*Dentry).releaseKeptDentriesLocked(0xc004865200, {0x13831b0, 0xc00251ca80})
	pkg/sentry/fsimpl/kernfs/filesystem.go:293 +0x245 fp=0xc0089e1380 sp=0xc0089e12a0 pc=0x7cdce5
gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs.(*Filesystem).Release(0xc00412d680, {0x13831b0, 0xc00251ca80})
	pkg/sentry/fsimpl/kernfs/filesystem.go:267 +0x7b fp=0xc0089e13b8 sp=0xc0089e1380 pc=0x7cd9db
gvisor.dev/gvisor/pkg/sentry/fsimpl/cgroupfs.(*filesystem).Release(0xc00412d680, {0x13831b0, 0xc00251ca80})
	pkg/sentry/fsimpl/cgroupfs/cgroupfs.go:474 +0x110 fp=0xc0089e13e8 sp=0xc0089e13b8 pc=0xc8f150
gvisor.dev/gvisor/pkg/sentry/vfs.(*Filesystem).DecRef.func1()
	pkg/sentry/vfs/filesystem.go:81 +0xbd fp=0xc0089e1428 sp=0xc0089e13e8 pc=0x74eedd
gvisor.dev/gvisor/pkg/sentry/vfs.(*FilesystemRefs).DecRef(0xc00054c101?, 0xc0089e14a0)
	bazel-out/k8-fastbuild-ST-246649c541f7/bin/pkg/sentry/vfs/filesystem_refs.go:131 +0x7e fp=0xc0089e1490 sp=0xc0089e1428 pc=0x74f79e
gvisor.dev/gvisor/pkg/sentry/vfs.(*Filesystem).DecRef(0x0?, {0x13831b0?, 0xc00251ca80?})
	pkg/sentry/vfs/filesystem.go:77 +0x5b fp=0xc0089e14d0 sp=0xc0089e1490 pc=0x74eddb
gvisor.dev/gvisor/pkg/sentry/vfs.(*Mount).destroy(0xc008332580, {0x13831b0, 0xc00251ca80})
	pkg/sentry/vfs/mount.go:926 +0x16d fp=0xc0089e1520 sp=0xc0089e14d0 pc=0x75936d
gvisor.dev/gvisor/pkg/sentry/vfs.(*Mount).DecRef(0xc008332580, {0x13831b0, 0xc00251ca80})
	pkg/sentry/vfs/mount.go:910 +0xa5 fp=0xc0089e1548 sp=0xc0089e1520 pc=0x7591c5
gvisor.dev/gvisor/pkg/sentry/vfs.VirtualDentry.DecRef({0xc008332580?, 0xc004865200?}, {0x13831b0, 0xc00251ca80})
	pkg/sentry/vfs/vfs.go:927 +0x6d fp=0xc0089e1578 sp=0xc0089e1548 pc=0x7686ad
gvisor.dev/gvisor/pkg/sentry/vfs.(*VirtualFilesystem).UmountAt.func1()
	pkg/sentry/vfs/mount.go:653 +0x36 fp=0xc0089e15a8 sp=0xc0089e1578 pc=0x7586f6
runtime.deferreturn()
	GOROOT/src/runtime/panic.go:436 +0x33 fp=0xc0089e15e8 sp=0xc0089e15a8 pc=0x4349d3
gvisor.dev/gvisor/pkg/sentry/vfs.(*VirtualFilesystem).UmountAt(0xc0005161d0, {0x13831b0, 0xc00251ca80}, 0xc0031d0800?, 0xc00a0cbf00?, 0xc0089e184c)
	pkg/sentry/vfs/mount.go:739 +0x945 fp=0xc0089e17c0 sp=0xc0089e15e8 pc=0x758305
gvisor.dev/gvisor/pkg/sentry/syscalls/linux.Umount2(0xc00251ca80, {{0x7f51a47d1580}, {0xa}, {0x7f51a47d158c}, {0x55a77573c7a3}, {0xffffffff}, {0x7f51a47d1350}})
	pkg/sentry/syscalls/linux/sys_mount.go:171 +0x326 fp=0xc0089e1958 sp=0xc0089e17c0 pc=0xac72a6
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0xc00251ca80, 0xa6, {{0x7f51a47d1580}, {0xa}, {0x7f51a47d158c}, {0x55a77573c7a3}, {0xffffffff}, {0x7f51a47d1350}})
	pkg/sentry/kernel/task_syscall.go:142 +0x80b fp=0xc0089e1c98 sp=0xc0089e1958 pc=0x9766ab
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0xc00251ca80, 0x85?, {{0x7f51a47d1580}, {0xa}, {0x7f51a47d158c}, {0x55a77573c7a3}, {0xffffffff}, {0x7f51a47d1350}})
	pkg/sentry/kernel/task_syscall.go:322 +0x54 fp=0xc0089e1cf8 sp=0xc0089e1c98 pc=0x977c94
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0x81018f?, 0x0?, {{0x7f51a47d1580}, {0xa}, {0x7f51a47d158c}, {0x55a77573c7a3}, {0xffffffff}, {0x7f51a47d1350}})
	pkg/sentry/kernel/task_syscall.go:282 +0x85 fp=0xc0089e1d58 sp=0xc0089e1cf8 pc=0x977885
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0xc0016b7d40?)
	pkg/sentry/kernel/task_syscall.go:257 +0x3ac fp=0xc0089e1e50 sp=0xc0089e1d58 pc=0x97754c
gvisor.dev/gvisor/pkg/sentry/kernel.(*runApp).execute(0x0?, 0xc00251ca80)
	pkg/sentry/kernel/task_run.go:253 +0x1125 fp=0xc0089e1f60 sp=0xc0089e1e50 pc=0x969465
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).run(0xc00251ca80, 0xb5e)
	pkg/sentry/kernel/task_run.go:94 +0x1ec fp=0xc0089e1fc0 sp=0xc0089e1f60 pc=0x967cac
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start.func1()
	pkg/sentry/kernel/task_start.go:378 +0x2a fp=0xc0089e1fe0 sp=0xc0089e1fc0 pc=0x974b4a
runtime.goexit()
	src/runtime/asm_amd64.s:1571 +0x1 fp=0xc0089e1fe8 sp=0xc0089e1fe0 pc=0x4695c1
created by gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start
	pkg/sentry/kernel/task_start.go:378 +0x105