panic: UserChainTarget should never be called.

goroutine 13374 gp=0x27f1126f6000 m=37 mp=0x27f111fab808 [running]:
panic({0x1bd63a0?, 0x1f2a9c0?})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/go/src/runtime/panic.go:879 +0x15c fp=0x27f1129c3f00 sp=0x27f1129c3e50 pc=0x9667c
gvisor.dev/gvisor/pkg/tcpip/stack.(*UserChainTarget).Action(...)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/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=0x27f1129c3f20 sp=0x27f1129c3f00 pc=0xebbda0
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).checkRule(0x2?, 0x1, 0x27f11266ef20, {{0x27f112966c08, 0x4, 0x4}, {0xffffffffffffffff, 0x1, 0x2, 0x0, ...}, ...}, ...)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/iptables.go:774 +0x3d0 fp=0x27f1129c4130 sp=0x27f1129c3f20 pc=0xbedaf0
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).checkChain(0x27f113213c08, 0x1, 0x27f11266ef20, {{0x27f112966c08, 0x4, 0x4}, {0xffffffffffffffff, 0x1, 0x2, 0x0, ...}, ...}, ...)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/iptables.go:705 +0x16c fp=0x27f1129c4220 sp=0x27f1129c4130 pc=0xbed25c
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).check(0xffffffffffffffff?, {{0x27f112966c08, 0x4, 0x4}, {0xffffffffffffffff, 0x1, 0x2, 0x0, 0xffffffffffffffff}, {0xffffffffffffffff, ...}}, ...)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/iptables.go:650 +0x114 fp=0x27f1129c43f0 sp=0x27f1129c4220 pc=0xbec9c4
gvisor.dev/gvisor/pkg/tcpip/stack.check(0x27f11266ef20?, {{0x27f112966c08, 0x4, 0x4}, {0xffffffffffffffff, 0x1, 0x2, 0x0, 0xffffffffffffffff}, {0xffffffffffffffff, ...}}, ...)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/iptables.go:640 +0xc4 fp=0x27f1129c44c0 sp=0x27f1129c43f0 pc=0xbec864
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).CheckInput(0x27f113213c08, 0x27f11266ef20, {0x27f1115b9c48, 0x7})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/iptables.go:459 +0x2b8 fp=0x27f1129c47f0 sp=0x27f1129c44c0 pc=0xbeb3c8
gvisor.dev/gvisor/pkg/tcpip/network/ipv6.(*endpoint).deliverPacketLocally(0x27f1115d6a88, {0x27f1122b480e, 0x28, 0xf2}, 0x27f11266ef20, {0x27f1115b9c48?, 0x5?})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/network/ipv6/ipv6.go:1436 +0x168 fp=0x27f1129c4a50 sp=0x27f1129c47f0 pc=0x1027738
gvisor.dev/gvisor/pkg/tcpip/network/ipv6.(*endpoint).handleValidatedPacket(0x27f1115d6a88, {0x27f1122b480e, 0x28, 0xf2}, 0x27f11266ef20, {0x27f1115b9c48, 0x7})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/network/ipv6/ipv6.go:1425 +0x1148 fp=0x27f1129c4d40 sp=0x27f1129c4a50 pc=0x10270f8
gvisor.dev/gvisor/pkg/tcpip/network/ipv6.(*endpoint).HandlePacket(0x27f1115d6a88, 0x27f11266ef20)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/network/ipv6/ipv6.go:1195 +0x1d80 fp=0x27f1129c52a0 sp=0x27f1129c4d40 pc=0x10205f0
gvisor.dev/gvisor/pkg/tcpip/stack.(*nic).DeliverNetworkPacket(0x27f111364488, 0x86dd, 0x27f11266ef20)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/nic.go:781 +0xa00 fp=0x27f1129c52e0 sp=0x27f1129c52a0 pc=0xc0e280
gvisor.dev/gvisor/pkg/tcpip/link/nested.(*Endpoint).DeliverNetworkPacket(0x27f111d17348?, 0x86dd, 0x27f11266ef20)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/link/nested/nested.go:61 +0x154 fp=0x27f1129c5320 sp=0x27f1129c52e0 pc=0x1070c44
gvisor.dev/gvisor/pkg/tcpip/link/packetsocket.(*Endpoint).DeliverNetworkPacket(0x27f11332c9b0, 0x86dd, 0x27f11266ef20)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/link/packetsocket/packetsocket.go:50 +0xa4 fp=0x27f1129c5350 sp=0x27f1129c5320 pc=0x1074794
gvisor.dev/gvisor/pkg/tcpip/link/channel.(*Endpoint).InjectInbound(0x27f11151db60, 0x86dd, 0x27f11266ef20)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/link/channel/channel.go:208 +0x18c fp=0x27f1129c5390 sp=0x27f1129c5350 pc=0x107c3ac
gvisor.dev/gvisor/pkg/tcpip/link/tun.(*Device).Write(0x27f111ba6d70, 0x27f11269f470)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/link/tun/device.go:279 +0x17f8 fp=0x27f1129c5540 sp=0x27f1129c5390 pc=0x1083238
gvisor.dev/gvisor/pkg/sentry/devices/tundev.(*tunFD).Write(0x1bd6420?, {0x1f583a0, 0x27f11215c588}, {{0x1f4d9f8, 0x27f112fa6008}, {0x0, 0x1, 0x20000640, 0xd2}, {0x0}}, ...)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/devices/tundev/tundev.go:176 +0x828 fp=0x27f1129c5600 sp=0x27f1129c5540 pc=0x1774b18
gvisor.dev/gvisor/pkg/sentry/vfs.(*FileDescription).Write(0x27f111ba6d00, {0x1f583a0, 0x27f11215c588}, {{0x1f4d9f8, 0x27f112fa6008}, {0x0, 0x1, 0x20000640, 0xd2}, {0x0}}, ...)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/vfs/file_description.go:728 +0x174 fp=0x27f1129c5680 sp=0x27f1129c5600 pc=0x707354
gvisor.dev/gvisor/pkg/sentry/syscalls/linux.write(0x27f11215c588, 0x27f111ba6d00, {{0x1f4d9f8, 0x27f112fa6008}, {0x0, 0x1, 0x20000640, 0xd2}, {0x0}}, {0x33fb8?})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/syscalls/linux/sys_read_write.go:333 +0xdc fp=0x27f1129c5800 sp=0x27f1129c5680 pc=0x11b677c
gvisor.dev/gvisor/pkg/sentry/syscalls/linux.Write(0x27f11215c588, 0x1a5?, {{0xc8}, {0x20000640}, {0xd2}, {0x0}, {0x0}, {0x0}})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/syscalls/linux/sys_read_write.go:304 +0x4c0 fp=0x27f1129c5940 sp=0x27f1129c5800 pc=0x11b4d80
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0x27f11215c588, 0x40, {{0xc8}, {0x20000640}, {0xd2}, {0x0}, {0x0}, {0x0}})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_syscall.go:143 +0x1230 fp=0x27f1129c5c80 sp=0x27f1129c5940 pc=0xe08340
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0x27f11215c588, 0x40, {{0xc8}, {0x20000640}, {0xd2}, {0x0}, {0x0}, {0x0}})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_syscall.go:323 +0xb0 fp=0x27f1129c5ce0 sp=0x27f1129c5c80 pc=0xe0b550
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0x27f11215c588, 0x40, {{0xc8}, {0x20000640}, {0xd2}, {0x0}, {0x0}, {0x0}})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_syscall.go:283 +0x14c fp=0x27f1129c5d30 sp=0x27f1129c5ce0 pc=0xe0a59c
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0x27f111ba7790?)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_syscall.go:258 +0x8cc fp=0x27f1129c5e10 sp=0x27f1129c5d30 pc=0xe09d6c
gvisor.dev/gvisor/pkg/sentry/kernel.(*runApp).execute(0x27f1125b5320?, 0x27f11215c588)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_run.go:258 +0x2fec fp=0x27f1129c5f10 sp=0x27f1129c5e10 pc=0xdea75c
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).run(0x27f11215c588, 0xa92)
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_run.go:89 +0x56c fp=0x27f1129c5fb0 sp=0x27f1129c5f10 pc=0xde6e6c
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start.gowrap1()
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_start.go:531 +0x20 fp=0x27f1129c5fd0 sp=0x27f1129c5fb0 pc=0xe04b80
runtime.goexit({})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/go/src/runtime/asm_arm64.s:1447 +0x4 fp=0x27f1129c5fd0 sp=0x27f1129c5fd0 pc=0x9ef54
created by gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start in goroutine 13454
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_start.go:531 +0x16c