panic: Incrementing non-positive ref count

goroutine 78 [running]:
gvisor.googlesource.com/gvisor/pkg/refs.(*AtomicRefCount).IncRef(0xc42092ca80)
	pkg/refs/refcounter.go:211 +0x5a
gvisor.googlesource.com/gvisor/pkg/sentry/mm.(*MemoryManager).createVMALocked(0xc420131900, 0xc75800, 0xc420669200, 0x1000, 0xc758c0, 0xc42092ca80, 0xc72780, 0xc42092ca80, 0x0, 0x20ffc000, ...)
	pkg/sentry/mm/vma.go:76 +0x436
gvisor.googlesource.com/gvisor/pkg/sentry/mm.(*MemoryManager).MMap(0xc420131900, 0xc75800, 0xc420669200, 0x1000, 0xc758c0, 0xc42092ca80, 0xc72780, 0xc42092ca80, 0x0, 0x20ffc000, ...)
	pkg/sentry/mm/syscalls.go:130 +0x1c6
gvisor.googlesource.com/gvisor/pkg/sentry/syscalls/linux.Shmat(0xc420669200, 0xba8, 0x20ffc000, 0x3000, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
	pkg/sentry/syscalls/linux/sys_shm.go:76 +0x252
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0xc420669200, 0x1e, 0xba8, 0x20ffc000, 0x3000, 0x0, 0x0, 0x0, 0xc420751ca8, 0xbb5a60, ...)
	pkg/sentry/kernel/task_syscall.go:162 +0x307
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0xc420669200, 0x1e, 0xba8, 0x20ffc000, 0x3000, 0x0, 0x0, 0x0, 0x0, 0x0)
	pkg/sentry/kernel/task_syscall.go:278 +0x62
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0xc420669200, 0x1e, 0xba8, 0x20ffc000, 0x3000, 0x0, 0x0, 0x0, 0xc4205aac00, 0xc420751e00)
	pkg/sentry/kernel/task_syscall.go:241 +0x91
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0xc420669200, 0x2, 0xc420400480)
	pkg/sentry/kernel/task_syscall.go:216 +0x10c
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*runApp).execute(0x0, 0xc420669200, 0xc689e0, 0x0)
	pkg/sentry/kernel/task_run.go:217 +0xed8
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).run(0xc420669200, 0x9)
	pkg/sentry/kernel/task_run.go:95 +0x174
created by gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).Start
	pkg/sentry/kernel/task_start.go:251 +0x100