panic: UserChainTarget should never be called.

goroutine 30917 gp=0x531c6bb2f680 m=94 mp=0x531c6db88008 [running]:
panic({0x1bd6420?, 0x1f2aea0?})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/go/src/runtime/panic.go:879 +0x15c fp=0x531c6df8df00 sp=0x531c6df8de50 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=0x531c6df8df20 sp=0x531c6df8df00 pc=0xebc2c0
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).checkRule(0x2?, 0x1, 0x531c6bec8c60, {{0x531c6c57f408, 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=0x531c6df8e130 sp=0x531c6df8df20 pc=0xbedff0
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).checkChain(0x531c6df46408, 0x1, 0x531c6bec8c60, {{0x531c6c57f408, 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=0x531c6df8e220 sp=0x531c6df8e130 pc=0xbed75c
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).check(0xffffffffffffffff?, {{0x531c6c57f408, 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=0x531c6df8e3f0 sp=0x531c6df8e220 pc=0xbecec4
gvisor.dev/gvisor/pkg/tcpip/stack.check(0x531c6bec8c60?, {{0x531c6c57f408, 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=0x531c6df8e4c0 sp=0x531c6df8e3f0 pc=0xbecd64
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).CheckInput(0x531c6df46408, 0x531c6bec8c60, {0x531c6d5afc18, 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=0x531c6df8e7f0 sp=0x531c6df8e4c0 pc=0xbeb8c8
gvisor.dev/gvisor/pkg/tcpip/network/ipv6.(*endpoint).deliverPacketLocally(0x531c6c392008, {0x531c6bbe710e, 0x30, 0x72}, 0x531c6bec8c60, {0x531c6d5afc18?, 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=0x531c6df8ea50 sp=0x531c6df8e7f0 pc=0x1027c58
gvisor.dev/gvisor/pkg/tcpip/network/ipv6.(*endpoint).handleValidatedPacket(0x531c6c392008, {0x531c6bbe710e, 0x30, 0x72}, 0x531c6bec8c60, {0x531c6d5afc18, 0x7})
	/syzkaller/.cache/bazel/_bazel_root/2defe4792b6e1aac1936903102d81265/sandbox/linux-sandbox/53/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/network/ipv6/ipv6.go:1425 +0x1148 fp=0x531c6df8ed40 sp=0x531c6df8ea50 pc=0x1027618
gvisor.dev/gvisor/pkg/tcpip/network/ipv6.(*endpoint).HandlePacket(0x531c6c392008, 0x531c6bec8c60)
	/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=0x531c6df8f2a0 sp=0x531c6df8ed40 pc=0x1020b10
gvisor.dev/gvisor/pkg/tcpip/stack.(*nic).DeliverNetworkPacket(0x531c6b7e9688, 0x86dd, 0x531c6bec8c60)
	/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=0x531c6df8f2e0 sp=0x531c6df8f2a0 pc=0xc0e7d0
gvisor.dev/gvisor/pkg/tcpip/link/nested.(*Endpoint).DeliverNetworkPacket(0x531c6c2e7348?, 0x86dd, 0x531c6bec8c60)
	/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=0x531c6df8f320 sp=0x531c6df8f2e0 pc=0x1071164
gvisor.dev/gvisor/pkg/tcpip/link/packetsocket.(*Endpoint).DeliverNetworkPacket(0x531c6c750500, 0x86dd, 0x531c6bec8c60)
	/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=0x531c6df8f350 sp=0x531c6df8f320 pc=0x1074cb4
gvisor.dev/gvisor/pkg/tcpip/link/channel.(*Endpoint).InjectInbound(0x531c6ce465a0, 0x86dd, 0x531c6bec8c60)
	/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=0x531c6df8f390 sp=0x531c6df8f350 pc=0x107c8cc
gvisor.dev/gvisor/pkg/tcpip/link/tun.(*Device).Write(0x531c6bc2b320, 0x531c6c6be9f0)
	/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=0x531c6df8f540 sp=0x531c6df8f390 pc=0x1083768
gvisor.dev/gvisor/pkg/sentry/devices/tundev.(*tunFD).Write(0x1bd64a0?, {0x1f588a0, 0x531c6c9bf208}, {{0x1f4def8, 0x531c6cf55008}, {0x0, 0x1, 0x20000000, 0x4a}, {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=0x531c6df8f600 sp=0x531c6df8f540 pc=0x1775bb8
gvisor.dev/gvisor/pkg/sentry/vfs.(*FileDescription).Write(0x531c6bc2b2b0, {0x1f588a0, 0x531c6c9bf208}, {{0x1f4def8, 0x531c6cf55008}, {0x0, 0x1, 0x20000000, 0x4a}, {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=0x531c6df8f680 sp=0x531c6df8f600 pc=0x707854
gvisor.dev/gvisor/pkg/sentry/syscalls/linux.write(0x531c6c9bf208, 0x531c6bc2b2b0, {{0x1f4def8, 0x531c6cf55008}, {0x0, 0x1, 0x20000000, 0x4a}, {0x0}}, {0x5ca5ae8?})
	/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=0x531c6df8f800 sp=0x531c6df8f680 pc=0x11b6cfc
gvisor.dev/gvisor/pkg/sentry/syscalls/linux.Write(0x531c6c9bf208, 0x5b2?, {{0xc8}, {0x20000000}, {0x4a}, {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=0x531c6df8f940 sp=0x531c6df8f800 pc=0x11b5300
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0x531c6c9bf208, 0x40, {{0xc8}, {0x20000000}, {0x4a}, {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=0x531c6df8fc80 sp=0x531c6df8f940 pc=0xe08760
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0x531c6c9bf208, 0x40, {{0xc8}, {0x20000000}, {0x4a}, {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=0x531c6df8fce0 sp=0x531c6df8fc80 pc=0xe0b970
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0x531c6c9bf208, 0x40, {{0xc8}, {0x20000000}, {0x4a}, {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=0x531c6df8fd30 sp=0x531c6df8fce0 pc=0xe0a9bc
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0x531c6cb6f1e0?)
	/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=0x531c6df8fe10 sp=0x531c6df8fd30 pc=0xe0a18c
gvisor.dev/gvisor/pkg/sentry/kernel.(*runApp).execute(0x531c6bedde60?, 0x531c6c9bf208)
	/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=0x531c6df8ff10 sp=0x531c6df8fe10 pc=0xdeab7c
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).run(0x531c6c9bf208, 0x1919)
	/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=0x531c6df8ffb0 sp=0x531c6df8ff10 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=0x531c6df8ffd0 sp=0x531c6df8ffb0 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=0x531c6df8ffd0 sp=0x531c6df8ffd0 pc=0x9ef54
created by gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start in goroutine 30915
	/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