panic: munmap(600000, 200000)) failed: function not implemented

goroutine 534228 [running]:
gvisor.dev/gvisor/pkg/sentry/platform/ptrace.(*subprocess).Unmap(0xc00011a080, 0x600000, 0x200000)
DIAGNOSIS:
I1210 20:11:20.182086    6352 x:0] ***************************
I1210 20:11:20.182099    6352 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-3]
I1210 20:11:20.182130    6352 x:0] Version release-20191129.0-30-g98aafb1334b8
I1210 20:11:20.182136    6352 x:0] PID: 6352
I1210 20:11:20.182144    6352 x:0] UID: 0, GID: 0
I1210 20:11:20.182148    6352 x:0] Configuration:
I1210 20:11:20.182157    6352 x:0] 		RootDir: /syzkaller/managers/ptrace-direct-overlay-host/workdir/gvisor_root
I1210 20:11:20.182162    6352 x:0] 		Platform: ptrace
I1210 20:11:20.182166    6352 x:0] 		FileAccess: shared, overlay: false
I1210 20:11:20.182183    6352 x:0] 		Network: host, logging: false
I1210 20:11:20.182191    6352 x:0] 		Strace: false, max size: 1024, syscalls: []
I1210 20:11:20.182195    6352 x:0] ***************************
D1210 20:11:20.183952    6352 x:0] Load container "/syzkaller/managers/ptrace-direct-overlay-host/workdir/gvisor_root" "ci-gvisor-ptrace-direct-overlay-host-3"
D1210 20:11:20.200923    6352 x:0] Signal container "ci-gvisor-ptrace-direct-overlay-host-3": signal 0
D1210 20:11:20.200969    6352 x:0] Signal sandbox "ci-gvisor-ptrace-direct-overlay-host-3"
D1210 20:11:20.200979    6352 x:0] Connecting to sandbox "ci-gvisor-ptrace-direct-overlay-host-3"
D1210 20:11:20.201273    6352 x:0] urpc: successfully marshalled 118 bytes.
I1210 20:11:20.651115    6352 x:0] Found sandbox "ci-gvisor-ptrace-direct-overlay-host-3", PID: 59549
I1210 20:11:20.651148    6352 x:0] Retrieving sandbox stacks
D1210 20:11:20.651153    6352 x:0] Stacks sandbox "ci-gvisor-ptrace-direct-overlay-host-3"
D1210 20:11:20.651160    6352 x:0] Connecting to sandbox "ci-gvisor-ptrace-direct-overlay-host-3"
D1210 20:11:20.651225    6352 x:0] urpc: successfully marshalled 36 bytes.
W1210 20:11:20.795341    6352 x:0] FATAL ERROR: retrieving stacks: getting sandbox "ci-gvisor-ptrace-direct-overlay-host-3" stacks: urpc method "debug.Stacks" failed: connection reset by peer
retrieving stacks: getting sandbox "ci-gvisor-ptrace-direct-overlay-host-3" stacks: urpc method "debug.Stacks" failed: connection reset by peer
W1210 20:11:20.795440    6352 x:0] Failure to execute command, err: 1