panic: munmap(7fee22c00000, 200000)) failed: function not implemented

goroutine 255 [running]:
gvisor.dev/gvisor/pkg/sentry/platform/ptrace.(*subprocess).Unmap(0xc00095c040, 0x7fee22c00000, 0x200000)
DIAGNOSIS:
I0731 08:57:41.530879   17579 x:0] ***************************
I0731 08:57:41.530958   17579 x:0] Args: [/syzkaller/managers/ptrace-direct-overlay-host/current/image -root /syzkaller/managers/ptrace-direct-overlay-host/workdir/gvisor_root -watchdog-action=panic -network=none -debug -alsologtostderr -platform=ptrace -file-access=shared -network=host debug -stacks ci-gvisor-ptrace-direct-overlay-host-1]
I0731 08:57:41.530978   17579 x:0] Version release-20190529.1-286-ge511c0e05f82
I0731 08:57:41.530997   17579 x:0] PID: 17579
I0731 08:57:41.531003   17579 x:0] UID: 0, GID: 0
I0731 08:57:41.531017   17579 x:0] Configuration:
I0731 08:57:41.531033   17579 x:0] 		RootDir: /syzkaller/managers/ptrace-direct-overlay-host/workdir/gvisor_root
I0731 08:57:41.531038   17579 x:0] 		Platform: ptrace
I0731 08:57:41.531043   17579 x:0] 		FileAccess: shared, overlay: false
I0731 08:57:41.531053   17579 x:0] 		Network: host, logging: false
I0731 08:57:41.531061   17579 x:0] 		Strace: false, max size: 1024, syscalls: []
I0731 08:57:41.531068   17579 x:0] ***************************
D0731 08:57:41.531414   17579 x:0] Load container "/syzkaller/managers/ptrace-direct-overlay-host/workdir/gvisor_root" "ci-gvisor-ptrace-direct-overlay-host-1"
D0731 08:57:41.532989   17579 x:0] Signal container "ci-gvisor-ptrace-direct-overlay-host-1": signal 0
D0731 08:57:41.533021   17579 x:0] Signal sandbox "ci-gvisor-ptrace-direct-overlay-host-1"
D0731 08:57:41.533040   17579 x:0] Connecting to sandbox "ci-gvisor-ptrace-direct-overlay-host-1"
D0731 08:57:41.533583   17579 x:0] urpc: successfully marshalled 118 bytes.
I0731 08:57:41.885478   17579 x:0] Found sandbox "ci-gvisor-ptrace-direct-overlay-host-1", PID: 62206
I0731 08:57:41.885509   17579 x:0] Retrieving sandbox stacks
D0731 08:57:41.885515   17579 x:0] Stacks sandbox "ci-gvisor-ptrace-direct-overlay-host-1"
D0731 08:57:41.885524   17579 x:0] Connecting to sandbox "ci-gvisor-ptrace-direct-overlay-host-1"
D0731 08:57:41.885621   17579 x:0] urpc: successfully marshalled 36 bytes.
W0731 08:57:41.981301   17579 x:0] FATAL ERROR: retrieving stacks: getting sandbox "ci-gvisor-ptrace-direct-overlay-host-1" stacks: urpc method "debug.Stacks" failed: connection reset by peer
retrieving stacks: getting sandbox "ci-gvisor-ptrace-direct-overlay-host-1" stacks: urpc method "debug.Stacks" failed: connection reset by peer
W0731 08:57:41.981394   17579 x:0] Failure to execute command, err: 1