panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0xc9e3df]

goroutine 339 [running]:
panic({0x184c6e0, 0x2795c50})
	GOROOT/src/runtime/panic.go:1147 +0x3a8 fp=0xc0007b2f48 sp=0xc0007b2e88 pc=0x437d08
runtime.panicmem(...)
	GOROOT/src/runtime/panic.go:221
runtime.sigpanic()
	GOROOT/src/runtime/signal_unix.go:735 +0x327 fp=0xc0007b2f98 sp=0xc0007b2f48 pc=0x450187
gvisor.dev/gvisor/pkg/sentry/kernel.(*ThreadGroup).MigrateCgroup(0x0, {0xc000402ea0, {0x1ccdba0, 0xc0007c9c00}})
	pkg/sentry/kernel/task_cgroup.go:140 +0x7f fp=0xc0007b30c0 sp=0xc0007b2f98 pc=0xc9e3df
gvisor.dev/gvisor/pkg/sentry/fsimpl/cgroupfs.(*cgroupProcsData).Write(0xc0005fc008, {0x1ce44f0, 0xc00047f500}, 0xc0002904c0, {{0x1cd74c8, 0xc0009ac000}, {0x0, 0x1, 0x20000080, 0xb}, ...}, ...)
	pkg/sentry/fsimpl/cgroupfs/base.go:305 +0x1c5 fp=0xc0007b3170 sp=0xc0007b30c0 pc=0x1040405
gvisor.dev/gvisor/pkg/sentry/vfs.(*DynamicBytesFileDescriptionImpl).pwriteLocked(0xc000290460, {0x1ce44f0, 0xc00047f500}, {{0x1cd74c8, 0xc0009ac000}, {0x0, 0x1, 0x20000080, 0xb}, {0x0, ...}}, ...)
	pkg/sentry/vfs/file_description_impl_util.go:381 +0x2c4 fp=0xc0007b32d0 sp=0xc0007b3170 pc=0x8dd244
gvisor.dev/gvisor/pkg/sentry/vfs.(*DynamicBytesFileDescriptionImpl).Write(0xc000290460, {0x1ce44f0, 0xc00047f500}, {{0x1cd74c8, 0xc0009ac000}, {0x0, 0x1, 0x20000080, 0xb}, {0x0, ...}}, ...)
	pkg/sentry/vfs/file_description_impl_util.go:402 +0x11d fp=0xc0007b33b0 sp=0xc0007b32d0 pc=0x8dd67d
gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs.(*DynamicBytesFD).Write(0xc000290460, {0x1ce44f0, 0xc00047f500}, {{0x1cd74c8, 0xc0009ac000}, {0x0, 0x1, 0x20000080, 0xb}, {0x0, ...}}, ...)
	pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go:125 +0x9b fp=0xc0007b3438 sp=0xc0007b33b0 pc=0xa5745b
gvisor.dev/gvisor/pkg/sentry/vfs.(*FileDescription).Write(0xc0002904c0, {0x1ce44f0, 0xc00047f500}, {{0x1cd74c8, 0xc0009ac000}, {0x0, 0x1, 0x20000080, 0xb}, {0x0, ...}}, ...)
	pkg/sentry/vfs/file_description.go:665 +0x125 fp=0xc0007b3508 sp=0xc0007b3438 pc=0x8d8625
gvisor.dev/gvisor/pkg/sentry/syscalls/linux/vfs2.write(0xc0002904c0, 0xc0002904c0, {{0x1cd74c8, 0xc0009ac000}, {0x0, 0x1, 0x20000080, 0xb}, {0x0, 0x1}}, ...)
	pkg/sentry/syscalls/linux/vfs2/read_write.go:348 +0x9d fp=0xc0007b3690 sp=0xc0007b3508 pc=0x1376c9d
gvisor.dev/gvisor/pkg/sentry/syscalls/linux/vfs2.Write(0xc00047f500, {{0x4}, {0x20000080}, {0xb}, {0x0}, {0x17}, {0x0}})
	pkg/sentry/syscalls/linux/vfs2/read_write.go:317 +0x2c5 fp=0xc0007b3830 sp=0xc0007b3690 pc=0x1376325
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0xc00047f500, 0x1, {{0x4}, {0x20000080}, {0xb}, {0x0}, {0x17}, {0x0}})
	pkg/sentry/kernel/task_syscall.go:103 +0x4dc fp=0xc0007b3a80 sp=0xc0007b3830 pc=0xccefdc
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0xc00047f500, 0x46f7f9, {{0x4}, {0x20000080}, {0xb}, {0x0}, {0x17}, {0x0}})
	pkg/sentry/kernel/task_syscall.go:238 +0x6a fp=0xc0007b3b08 sp=0xc0007b3a80 pc=0xcd008a
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0xc0005dc1e0, 0x46fcac, {{0x4}, {0x20000080}, {0xb}, {0x0}, {0x17}, {0x0}})
	pkg/sentry/kernel/task_syscall.go:198 +0x8f fp=0xc0007b3b80 sp=0xc0007b3b08 pc=0xccfb0f
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0xc00047f500)
	pkg/sentry/kernel/task_syscall.go:173 +0x3c5 fp=0xc0007b3c88 sp=0xc0007b3b80 pc=0xccf745
gvisor.dev/gvisor/pkg/sentry/kernel.(*runApp).execute(0xc00047f500, 0xc00047f500)
	pkg/sentry/kernel/task_run.go:254 +0x1698 fp=0xc0007b3eb8 sp=0xc0007b3c88 pc=0xcbc098
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).run(0xc00047f500, 0xe)
	pkg/sentry/kernel/task_run.go:95 +0x35b fp=0xc0007b3fb0 sp=0xc0007b3eb8 pc=0xcb9fdb
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start·dwrap·236()
	pkg/sentry/kernel/task_start.go:339 +0x48 fp=0xc0007b3fe0 sp=0xc0007b3fb0 pc=0xcccfe8
runtime.goexit()
	src/runtime/asm_amd64.s:1581 +0x1 fp=0xc0007b3fe8 sp=0xc0007b3fe0 pc=0x46e081
created by gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start
	pkg/sentry/kernel/task_start.go:339 +0x1a9