On Wed, Apr 05, 2017 at 05:00:07PM -0700, R. Parameswaran wrote: > > Change-set here uses the new kernel function, kernel_sock_ip_overhead(), > to factor the outer IP overhead on the L2TP tunnel socket (including > IP Options, if any) when calculating the default MTU for an Ethernet > pseudowire, along with consideration of the inner Ethernet header. > I get the following warning with CONFIG_LOCKDEP when creating a new session: # ip l2tp add tunnel local 10.1.8.64 remote 10.1.8.32 udp_sport 1701 udp_dport 1701 tunnel_id 1 peer_tunnel_id 1 # ip l2tp add session tunnel_id 1 session_id 1 peer_session_id 1 ... [ 45.524535] ------------[ cut here ]------------ [ 45.524570] WARNING: CPU: 3 PID: 732 at ./include/net/sock.h:1509 kernel_sock_ip_overhead+0x54/0x1a1 [ 45.524574] Modules linked in: l2tp_eth l2tp_netlink l2tp_core ip6_udp_tunnel udp_tunnel crc32c_intel ghash_clmulni_intel pcbc aesni_intel aes_x86_64 crypto_simd cryptd glue_helper evdev acpi_cpufreq processor button serio_raw ext4 crc16 jbd2 mbcache virtio_blk virtio_net virtio_pci virtio_ring virtio [ 45.524696] CPU: 3 PID: 732 Comm: ip Not tainted 4.11.0-rc5 #1 [ 45.524700] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 [ 45.524704] Call Trace: [ 45.524714] dump_stack+0x67/0x90 [ 45.524725] __warn+0xfd/0x118 [ 45.524739] warn_slowpath_null+0x18/0x1a [ 45.524747] kernel_sock_ip_overhead+0x54/0x1a1 [ 45.524761] l2tp_eth_create+0x1eb/0x557 [l2tp_eth] [ 45.524768] ? __mutex_unlock_slowpath+0xb5/0x2c2 [ 45.524787] ? l2tp_eth_dev_uninit+0xd9/0xd9 [l2tp_eth] [ 45.524800] l2tp_nl_cmd_session_create+0x521/0x56b [l2tp_netlink] [ 45.524827] genl_family_rcv_msg+0x445/0x4b3 [ 45.524857] genl_rcv_msg+0x60/0x84 [ 45.524867] ? genl_family_rcv_msg+0x4b3/0x4b3 [ 45.524875] netlink_rcv_skb+0x95/0x102 [ 45.524881] ? down_read+0x41/0x62 [ 45.524893] genl_rcv+0x23/0x32 [ 45.524901] netlink_unicast+0x1b0/0x23b [ 45.524915] netlink_sendmsg+0x46f/0x48f [ 45.524933] ? netlink_unicast+0x23b/0x23b [ 45.524942] sock_sendmsg_nosec+0x41/0x51 [ 45.524953] sock_sendmsg+0x33/0x38 [ 45.524962] ___sys_sendmsg+0x2a0/0x374 [ 45.524991] ? do_raw_spin_unlock+0xc2/0xcc [ 45.525002] ? _raw_spin_unlock+0x22/0x25 [ 45.525014] ? match_held_lock+0x20/0x113 [ 45.525027] ? __fget_light+0x89/0xae [ 45.525045] __sys_sendmsg+0x40/0x6b [ 45.525052] ? __sys_sendmsg+0x40/0x6b [ 45.525075] SyS_sendmsg+0x9/0xb [ 45.525083] entry_SYSCALL_64_fastpath+0x18/0xad [ 45.525089] RIP: 0033:0x7fb224391690 [ 45.525094] RSP: 002b:00007ffe53943dd8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e [ 45.525104] RAX: ffffffffffffffda RBX: 00007ffe539480f0 RCX: 00007fb224391690 [ 45.525108] RDX: 0000000000000000 RSI: 00007ffe53943e20 RDI: 0000000000000004 [ 45.525113] RBP: ffffffff810a1e49 R08: 0000000000000000 R09: 0000000000000005 [ 45.525119] R10: 0000000000000000 R11: 0000000000000246 R12: ffff88003436ff98 [ 45.525124] R13: 0000000000000046 R14: 00007ffe539486a0 R15: 00007ffe53947ea0 [ 45.525136] ? trace_hardirqs_off_caller+0x121/0x12f [ 45.525157] ---[ end trace 0834023e7b30e761 ]---
I guess you neet to lock_sock(tunnel->socket) before calling kernel_sock_ip_overhead().
