panic: UserChainTarget should never be called.

goroutine 9319 gp=0x29d75e790000 m=41 mp=0x29d75e37e008 [running]:
panic({0x1bd6420?, 0x1f2aea0?})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/go/src/runtime/panic.go:879 +0x15c fp=0x29d75e14ff00 sp=0x29d75e14fe50 pc=0x9667c
gvisor.dev/gvisor/pkg/tcpip/stack.(*UserChainTarget).Action(...)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/iptables_targets.go:174
gvisor.dev/gvisor/pkg/sentry/socket/netfilter.(*userChainTarget).Action(0x0?, 0x0?, 0x0?, 0x10?, {0x0?, 0x0?})
	<autogenerated>:1 +0x80 fp=0x29d75e14ff20 sp=0x29d75e14ff00 pc=0xebc2c0
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).checkRule(0x2?, 0x1, 0x29d75d4eba20, {{0x29d75dbfd008, 0x4, 0x4}, {0xffffffffffffffff, 0x1, 0x2, 0x0, ...}, ...}, ...)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/iptables.go:774 +0x3d0 fp=0x29d75e150130 sp=0x29d75e14ff20 pc=0xbedff0
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).checkChain(0x29d75e29c008, 0x1, 0x29d75d4eba20, {{0x29d75dbfd008, 0x4, 0x4}, {0xffffffffffffffff, 0x1, 0x2, 0x0, ...}, ...}, ...)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/iptables.go:705 +0x16c fp=0x29d75e150220 sp=0x29d75e150130 pc=0xbed75c
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).check(0xffffffffffffffff?, {{0x29d75dbfd008, 0x4, 0x4}, {0xffffffffffffffff, 0x1, 0x2, 0x0, 0xffffffffffffffff}, {0xffffffffffffffff, ...}}, ...)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/iptables.go:650 +0x114 fp=0x29d75e1503f0 sp=0x29d75e150220 pc=0xbecec4
gvisor.dev/gvisor/pkg/tcpip/stack.check(0x29d75d4eba20?, {{0x29d75dbfd008, 0x4, 0x4}, {0xffffffffffffffff, 0x1, 0x2, 0x0, 0xffffffffffffffff}, {0xffffffffffffffff, ...}}, ...)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/iptables.go:640 +0xc4 fp=0x29d75e1504c0 sp=0x29d75e1503f0 pc=0xbecd64
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).CheckInput(0x29d75e29c008, 0x29d75d4eba20, {0x29d75e112b48, 0x7})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/iptables.go:459 +0x2b8 fp=0x29d75e1507f0 sp=0x29d75e1504c0 pc=0xbeb8c8
gvisor.dev/gvisor/pkg/tcpip/network/ipv6.(*endpoint).deliverPacketLocally(0x29d75e1dd508, {0x29d75eaf1a0e, 0x28, 0xf2}, 0x29d75d4eba20, {0x29d75e112b48?, 0x5?})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/network/ipv6/ipv6.go:1436 +0x168 fp=0x29d75e150a50 sp=0x29d75e1507f0 pc=0x1027c58
gvisor.dev/gvisor/pkg/tcpip/network/ipv6.(*endpoint).handleValidatedPacket(0x29d75e1dd508, {0x29d75eaf1a0e, 0x28, 0xf2}, 0x29d75d4eba20, {0x29d75e112b48, 0x7})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/network/ipv6/ipv6.go:1409 +0xcd8 fp=0x29d75e150d40 sp=0x29d75e150a50 pc=0x10271a8
gvisor.dev/gvisor/pkg/tcpip/network/ipv6.(*endpoint).HandlePacket(0x29d75e1dd508, 0x29d75d4eba20)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/network/ipv6/ipv6.go:1195 +0x1d80 fp=0x29d75e1512a0 sp=0x29d75e150d40 pc=0x1020b10
gvisor.dev/gvisor/pkg/tcpip/stack.(*nic).DeliverNetworkPacket(0x29d75d9e4508, 0x86dd, 0x29d75d4eba20)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/nic.go:783 +0xa00 fp=0x29d75e1512e0 sp=0x29d75e1512a0 pc=0xc0e7d0
gvisor.dev/gvisor/pkg/tcpip/link/nested.(*Endpoint).DeliverNetworkPacket(0x29d75e625348?, 0x86dd, 0x29d75d4eba20)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/link/nested/nested.go:61 +0x154 fp=0x29d75e151320 sp=0x29d75e1512e0 pc=0x1071164
gvisor.dev/gvisor/pkg/tcpip/link/packetsocket.(*Endpoint).DeliverNetworkPacket(0x29d75e7b46e0, 0x86dd, 0x29d75d4eba20)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/link/packetsocket/packetsocket.go:50 +0xa4 fp=0x29d75e151350 sp=0x29d75e151320 pc=0x1074cb4
gvisor.dev/gvisor/pkg/tcpip/link/channel.(*Endpoint).InjectInbound(0x29d75da246c0, 0x86dd, 0x29d75d4eba20)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/link/channel/channel.go:208 +0x18c fp=0x29d75e151390 sp=0x29d75e151350 pc=0x107c8cc
gvisor.dev/gvisor/pkg/tcpip/link/tun.(*Device).Write(0x29d75e98b8d0, 0x29d75e6bb410)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/link/tun/device.go:279 +0x17f8 fp=0x29d75e151540 sp=0x29d75e151390 pc=0x1083768
gvisor.dev/gvisor/pkg/sentry/devices/tundev.(*tunFD).Write(0x1bd64a0?, {0x1f588a0, 0x29d75d839208}, {{0x1f4def8, 0x29d75ec7d008}, {0x0, 0x1, 0x20000280, 0xd2}, {0x0}}, ...)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/devices/tundev/tundev.go:176 +0x828 fp=0x29d75e151600 sp=0x29d75e151540 pc=0x1775bb8
gvisor.dev/gvisor/pkg/sentry/vfs.(*FileDescription).Write(0x29d75e98b860, {0x1f588a0, 0x29d75d839208}, {{0x1f4def8, 0x29d75ec7d008}, {0x0, 0x1, 0x20000280, 0xd2}, {0x0}}, ...)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/vfs/file_description.go:728 +0x174 fp=0x29d75e151680 sp=0x29d75e151600 pc=0x707854
gvisor.dev/gvisor/pkg/sentry/syscalls/linux.write(0x29d75d839208, 0x29d75e98b860, {{0x1f4def8, 0x29d75ec7d008}, {0x0, 0x1, 0x20000280, 0xd2}, {0x0}}, {0x1477a4?})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/syscalls/linux/sys_read_write.go:333 +0xdc fp=0x29d75e151800 sp=0x29d75e151680 pc=0x11b6cfc
gvisor.dev/gvisor/pkg/sentry/syscalls/linux.Write(0x29d75d839208, 0x2d2?, {{0xc8}, {0x20000280}, {0xd2}, {0x0}, {0x0}, {0x0}})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/syscalls/linux/sys_read_write.go:304 +0x4c0 fp=0x29d75e151940 sp=0x29d75e151800 pc=0x11b5300
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0x29d75d839208, 0x40, {{0xc8}, {0x20000280}, {0xd2}, {0x0}, {0x0}, {0x0}})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_syscall.go:143 +0x1230 fp=0x29d75e151c80 sp=0x29d75e151940 pc=0xe08760
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0x29d75d839208, 0x40, {{0xc8}, {0x20000280}, {0xd2}, {0x0}, {0x0}, {0x0}})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_syscall.go:323 +0xb0 fp=0x29d75e151ce0 sp=0x29d75e151c80 pc=0xe0b970
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0x29d75d839208, 0x40, {{0xc8}, {0x20000280}, {0xd2}, {0x0}, {0x0}, {0x0}})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_syscall.go:283 +0x14c fp=0x29d75e151d30 sp=0x29d75e151ce0 pc=0xe0a9bc
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0x29d75d556dd0?)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_syscall.go:258 +0x8cc fp=0x29d75e151e10 sp=0x29d75e151d30 pc=0xe0a18c
gvisor.dev/gvisor/pkg/sentry/kernel.(*runApp).execute(0x29d75e4481b0?, 0x29d75d839208)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_run.go:258 +0x2fec fp=0x29d75e151f10 sp=0x29d75e151e10 pc=0xdeab7c
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).run(0x29d75d839208, 0x8e3)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_run.go:89 +0x56c fp=0x29d75e151fb0 sp=0x29d75e151f10 pc=0xde728c
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start.gowrap1()
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_start.go:531 +0x20 fp=0x29d75e151fd0 sp=0x29d75e151fb0 pc=0xe04fa0
runtime.goexit({})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/go/src/runtime/asm_arm64.s:1447 +0x4 fp=0x29d75e151fd0 sp=0x29d75e151fd0 pc=0x9ef54
created by gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start in goroutine 11448
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_start.go:531 +0x16c