panic: UserChainTarget should never be called.

goroutine 479 gp=0x3f4db9beaf00 m=12 mp=0x3f4db9088008 [running]:
panic({0x19f9a80?, 0x1d531d0?})
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/go/src/runtime/panic.go:879 +0x16f fp=0x3f4dba785f60 sp=0x3f4dba785eb0 pc=0x48caaf
gvisor.dev/gvisor/pkg/tcpip/stack.(*UserChainTarget).Action(...)
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/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 +0x5e fp=0x3f4dba785f80 sp=0x3f4dba785f60 pc=0xfa43be
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).checkRule(0x0?, 0x1, 0x3f4db9c46160, {{0x3f4db9cca008, 0x4, 0x4}, {0xffffffffffffffff, 0x1, 0x2, 0x0, ...}, ...}, ...)
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/iptables.go:774 +0x342 fp=0x3f4dba786190 sp=0x3f4dba785f80 pc=0xd86be2
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).checkChain(0x3f4dba28e008, 0x1, 0x3f4db9c46160, {{0x3f4db9cca008, 0x4, 0x4}, {0xffffffffffffffff, 0x1, 0x2, 0x0, ...}, ...}, ...)
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/iptables.go:705 +0x17f fp=0x3f4dba786280 sp=0x3f4dba786190 pc=0xd864ff
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).check(0x3?, {{0x3f4db9cca008, 0x4, 0x4}, {0xffffffffffffffff, 0x1, 0x2, 0x0, 0xffffffffffffffff}, {0xffffffffffffffff, ...}}, ...)
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/iptables.go:650 +0x145 fp=0x3f4dba786450 sp=0x3f4dba786280 pc=0xd85dc5
gvisor.dev/gvisor/pkg/tcpip/stack.check(0x1d79810?, {{0x3f4db9cca008, 0x4, 0x4}, {0xffffffffffffffff, 0x1, 0x2, 0x0, 0xffffffffffffffff}, {0xffffffffffffffff, ...}}, ...)
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/iptables.go:640 +0xdf fp=0x3f4dba786518 sp=0x3f4dba786450 pc=0xd85bdf
gvisor.dev/gvisor/pkg/tcpip/stack.(*IPTables).CheckInput(0x3f4dba28e008, 0x3f4db9c46160, {0x3f4db97c2a68, 0x7})
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/iptables.go:459 +0x2e3 fp=0x3f4dba786848 sp=0x3f4dba786518 pc=0xd84883
gvisor.dev/gvisor/pkg/tcpip/network/ipv6.(*endpoint).deliverPacketLocally(0x3f4db8b21508, {0x3f4db92ac08e, 0x30, 0x72}, 0x3f4db9c46160, {0x3f4db97c2a68?, 0x0?})
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/network/ipv6/ipv6.go:1436 +0x13f fp=0x3f4dba786aa0 sp=0x3f4dba786848 pc=0x10a57ff
gvisor.dev/gvisor/pkg/tcpip/network/ipv6.(*endpoint).handleValidatedPacket(0x3f4db8b21508, {0x3f4db92ac08e, 0x30, 0x72}, 0x3f4db9c46160, {0x3f4db97c2a68, 0x7})
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/network/ipv6/ipv6.go:1425 +0xc3a fp=0x3f4dba786d88 sp=0x3f4dba786aa0 pc=0x10a549a
gvisor.dev/gvisor/pkg/tcpip/network/ipv6.(*endpoint).HandlePacket(0x3f4db8b21508, 0x3f4db9c46160)
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/network/ipv6/ipv6.go:1195 +0x1178 fp=0x3f4dba7872e8 sp=0x3f4dba786d88 pc=0x10a0c38
gvisor.dev/gvisor/pkg/tcpip/stack.(*nic).DeliverNetworkPacket(0x3f4db98e6488, 0x86dd, 0x3f4db9c46160)
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/stack/nic.go:781 +0x5ca fp=0x3f4dba787320 sp=0x3f4dba7872e8 pc=0xd9da4a
gvisor.dev/gvisor/pkg/tcpip/link/nested.(*Endpoint).DeliverNetworkPacket(0x908a05?, 0x86dd, 0x3f4db9c46160)
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/link/nested/nested.go:61 +0xc9 fp=0x3f4dba787358 sp=0x3f4dba787320 pc=0x10dd4a9
gvisor.dev/gvisor/pkg/tcpip/link/packetsocket.(*Endpoint).DeliverNetworkPacket(0x3f4db9a24460, 0x86dd, 0x3f4db9c46160)
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/link/packetsocket/packetsocket.go:50 +0x71 fp=0x3f4dba787380 sp=0x3f4dba787358 pc=0x10dfeb1
gvisor.dev/gvisor/pkg/tcpip/link/channel.(*Endpoint).InjectInbound(0x3f4db98c64e0, 0x86dd, 0x3f4db9c46160)
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/link/channel/channel.go:208 +0xf4 fp=0x3f4dba7873b8 sp=0x3f4dba787380 pc=0x10e5834
gvisor.dev/gvisor/pkg/tcpip/link/tun.(*Device).Write(0x3f4db9889180, 0x3f4db8d5f950)
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/tcpip/link/tun/device.go:279 +0xdb6 fp=0x3f4dba787570 sp=0x3f4dba7873b8 pc=0x10ea336
gvisor.dev/gvisor/pkg/sentry/devices/tundev.(*tunFD).Write(0x3f4db99c8000?, {0x1d83ea0, 0x3f4db97ab908}, {{0x1d78ef8, 0x3f4dba2a9008}, {0x0, 0x1, 0x2000000001c0, 0x4a}, {0x0}}, ...)
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/devices/tundev/tundev.go:176 +0x568 fp=0x3f4dba787638 sp=0x3f4dba787570 pc=0x1642048
gvisor.dev/gvisor/pkg/sentry/vfs.(*FileDescription).Write(0x3f4db9889110, {0x1d83ea0, 0x3f4db97ab908}, {{0x1d78ef8, 0x3f4dba2a9008}, {0x0, 0x1, 0x2000000001c0, 0x4a}, {0x0}}, ...)
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/vfs/file_description.go:728 +0x113 fp=0x3f4dba7876b8 sp=0x3f4dba787638 pc=0xa0abd3
gvisor.dev/gvisor/pkg/sentry/syscalls/linux.write(0x3f4db97ab908, 0x3f4db9889110, {{0x1d78ef8, 0x3f4dba2a9008}, {0x0, 0x1, 0x2000000001c0, 0x4a}, {0x0}}, {0x0})
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/syscalls/linux/sys_read_write.go:333 +0xea fp=0x3f4dba787848 sp=0x3f4dba7876b8 pc=0x11d43ca
gvisor.dev/gvisor/pkg/sentry/syscalls/linux.Write(0x3f4db97ab908, 0x3f4db99c7000?, {{0xc8}, {0x2000000001c0}, {0x4a}, {0x0}, {0x0}, {0x0}})
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/syscalls/linux/sys_read_write.go:304 +0x325 fp=0x3f4dba787988 sp=0x3f4dba787848 pc=0x11d2fa5
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0x3f4db97ab908, 0x1, {{0xc8}, {0x2000000001c0}, {0x4a}, {0x0}, {0x0}, {0x0}})
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_syscall.go:143 +0xcae fp=0x3f4dba787cc8 sp=0x3f4dba787988 pc=0xf1aeae
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0x3f4db97ab908, 0x1, {{0xc8}, {0x2000000001c0}, {0x4a}, {0x0}, {0x0}, {0x0}})
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_syscall.go:323 +0x86 fp=0x3f4dba787d20 sp=0x3f4dba787cc8 pc=0xf1d1e6
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0x3f4db97ab908, 0x1, {{0xc8}, {0x2000000001c0}, {0x4a}, {0x0}, {0x0}, {0x0}})
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_syscall.go:283 +0xc8 fp=0x3f4dba787d70 sp=0x3f4dba787d20 pc=0xf1c868
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0x3f4db9abc2c0?)
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_syscall.go:258 +0x5bf fp=0x3f4dba787e48 sp=0x3f4dba787d70 pc=0xf1c2bf
gvisor.dev/gvisor/pkg/sentry/kernel.(*runApp).execute(0x3f4db8b48480?, 0x3f4db97ab908)
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_run.go:258 +0x1fcb fp=0x3f4dba787f30 sp=0x3f4dba787e48 pc=0xf06eeb
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).run(0x3f4db97ab908, 0x5c)
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_run.go:89 +0x3de fp=0x3f4dba787fc0 sp=0x3f4dba787f30 pc=0xf0483e
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start.gowrap1()
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_start.go:531 +0x1b fp=0x3f4dba787fe0 sp=0x3f4dba787fc0 pc=0xf1883b
runtime.goexit({})
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/go/src/runtime/asm_amd64.s:1771 +0x1 fp=0x3f4dba787fe8 sp=0x3f4dba787fe0 pc=0x495761
created by gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start in goroutine 477
	/syzkaller/.cache/bazel/_bazel_root/e46b623d9124efeebe6def9c4e64353e/sandbox/linux-sandbox/124/execroot/_main/gopath/src/gvisor.dev/gvisor/pkg/sentry/kernel/task_start.go:531 +0x110