panic: ptrace status unexpected: got 31, wanted stopped

goroutine 1703403 [running]:
gvisor.googlesource.com/gvisor/pkg/sentry/platform/ptrace.(*thread).wait(0xc0016e9e00, 0x0, 0x1fca)
	pkg/sentry/platform/ptrace/subprocess.go:323 +0x4b9
gvisor.googlesource.com/gvisor/pkg/sentry/platform/ptrace.(*thread).syscall(0xc0016e9e00, 0xc000e1f218, 0xc000e1f3b8, 0x6, 0x6)
	pkg/sentry/platform/ptrace/subprocess.go:390 +0x10f
gvisor.googlesource.com/gvisor/pkg/sentry/platform/ptrace.(*thread).syscallIgnoreInterrupt(0xc0016e9e00, 0xc0016e9e10, 0x9, 0xc000e1f3b8, 0x6, 0x6, 0x101, 0x0, 0xb)
	pkg/sentry/platform/ptrace/subprocess.go:428 +0xd3
gvisor.googlesource.com/gvisor/pkg/sentry/platform/ptrace.(*subprocess).syscall(0xc0008f0080, 0x9, 0xc000e1f3b8, 0x6, 0x6, 0x0, 0x0, 0x0)
	pkg/sentry/platform/ptrace/subprocess.go:562 +0xf6
gvisor.googlesource.com/gvisor/pkg/sentry/platform/ptrace.(*subprocess).MapFile(0xc0008f0080, 0x2b169aa22000, 0x1308120, 0xc0002b2000, 0x1712b000, 0x1714c000, 0x2b1600000101, 0xc001236c00, 0x7)
	pkg/sentry/platform/ptrace/subprocess.go:571 +0x132
gvisor.googlesource.com/gvisor/pkg/sentry/mm.(*MemoryManager).mapASLocked(0xc000351b00, 0xc001236c00, 0x6, 0x2b169aa22000, 0x2b169aa43000, 0x2b169aa22000, 0x2b169aa43000, 0x0)
	pkg/sentry/mm/address_space.go:186 +0x41c
gvisor.googlesource.com/gvisor/pkg/sentry/mm.(*MemoryManager).populateVMAAndUnlock(0xc000351b00, 0x130ffe0, 0xc0012e0000, 0xc001a55500, 0xb, 0x2b169aa22000, 0x2b169aa43000, 0x0)
	pkg/sentry/mm/syscalls.go:241 +0x292
gvisor.googlesource.com/gvisor/pkg/sentry/mm.(*MemoryManager).MMap(0xc000351b00, 0x130ffe0, 0xc0012e0000, 0x21000, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
	pkg/sentry/mm/syscalls.go:157 +0x397
gvisor.googlesource.com/gvisor/pkg/sentry/syscalls/linux.Mmap(0xc0012e0000, 0x0, 0x21000, 0x3, 0x20022, 0xffffffffffffffff, 0x0, 0x0, 0x0, 0x0, ...)
	pkg/sentry/syscalls/linux/sys_mmap.go:104 +0x336
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0xc0012e0000, 0x9, 0x0, 0x21000, 0x3, 0x20022, 0xffffffffffffffff, 0x0, 0x465bc1, 0xc0012e07d8, ...)
	pkg/sentry/kernel/task_syscall.go:165 +0x408
DIAGNOSIS:
I0521 12:48:42.147906   27359 x:0] ***************************
I0521 12:48:42.148057   27359 x:0] Args: [/syzkaller/managers/ptrace-proxy-sandbox-race/current/image -root /syzkaller/managers/ptrace-proxy-sandbox-race/workdir/gvisor_root -watchdog-action=panic -network=none -debug -platform=ptrace -file-access=shared -network=sandbox debug -stacks ci-gvisor-ptrace-proxy-sandbox-race-0]
I0521 12:48:42.148113   27359 x:0] Version release-20190304.1-212-g80cc2c78e523
I0521 12:48:42.148131   27359 x:0] PID: 27359
I0521 12:48:42.148147   27359 x:0] UID: 0, GID: 0
I0521 12:48:42.148165   27359 x:0] Configuration:
I0521 12:48:42.148176   27359 x:0] 		RootDir: /syzkaller/managers/ptrace-proxy-sandbox-race/workdir/gvisor_root
I0521 12:48:42.148190   27359 x:0] 		Platform: ptrace
I0521 12:48:42.148237   27359 x:0] 		FileAccess: shared, overlay: false
I0521 12:48:42.148255   27359 x:0] 		Network: sandbox, logging: false
I0521 12:48:42.148286   27359 x:0] 		Strace: false, max size: 1024, syscalls: []
I0521 12:48:42.148312   27359 x:0] ***************************
D0521 12:48:42.149203   27359 x:0] Load container "/syzkaller/managers/ptrace-proxy-sandbox-race/workdir/gvisor_root" "ci-gvisor-ptrace-proxy-sandbox-race-0"
D0521 12:48:42.170762   27359 x:0] Signal container "ci-gvisor-ptrace-proxy-sandbox-race-0": signal 0
D0521 12:48:42.170866   27359 x:0] Signal sandbox "ci-gvisor-ptrace-proxy-sandbox-race-0"
D0521 12:48:42.170902   27359 x:0] Connecting to sandbox "ci-gvisor-ptrace-proxy-sandbox-race-0"
D0521 12:48:42.173892   27359 x:0] urpc: successfully marshalled 117 bytes.
I0521 12:48:43.038364   27359 x:0] Found sandbox "ci-gvisor-ptrace-proxy-sandbox-race-0", PID: 19506
I0521 12:48:43.038430   27359 x:0] Retrieving sandbox stacks
D0521 12:48:43.038838   27359 x:0] Stacks sandbox "ci-gvisor-ptrace-proxy-sandbox-race-0"
D0521 12:48:43.038877   27359 x:0] Connecting to sandbox "ci-gvisor-ptrace-proxy-sandbox-race-0"
D0521 12:48:43.038986   27359 x:0] urpc: successfully marshalled 36 bytes.
W0521 12:48:43.167814   27359 x:0] FATAL ERROR: retrieving stacks: getting sandbox "ci-gvisor-ptrace-proxy-sandbox-race-0" stacks: urpc method "debug.Stacks" failed: connection reset by peer
retrieving stacks: getting sandbox "ci-gvisor-ptrace-proxy-sandbox-race-0" stacks: urpc method "debug.Stacks" failed: connection reset by peer