KCSAN: data-race in dev_fetch_sw_netstats / iptunnel_xmit

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fa02fcd9 Merge tag 'media/v5.10-2' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10cc79b3500000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9b19d1bde60f8d
dashboard link: https://syzkaller.appspot.com/bug?extid=4a0f464b5f2ec554de26
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [da...@davemloft.net ku...@kernel.org kuz...@ms2.inr.ac.ru linux-...@vger.kernel.org net...@vger.kernel.org yosh...@linux-ipv6.org]

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4a0f46...@syzkaller.appspotmail.com

batman_adv: batadv0: Interface activated: batadv_slave_1
==================================================================
BUG: KCSAN: data-race in dev_fetch_sw_netstats / iptunnel_xmit

read-write to 0xffffe8ffffc66ef0 of 8 bytes by task 12519 on cpu 0:
iptunnel_xmit_stats include/net/ip_tunnels.h:451 [inline]
iptunnel_xmit+0x39e/0x460 net/ipv4/ip_tunnel_core.c:87
udp_tunnel_xmit_skb+0x15d/0x170 net/ipv4/udp_tunnel_core.c:190
send4+0x386/0x530 drivers/net/wireguard/socket.c:85
wg_socket_send_skb_to_peer+0x92/0x120 drivers/net/wireguard/socket.c:174
wg_packet_create_data_done drivers/net/wireguard/send.c:252 [inline]
wg_packet_tx_worker+0x1e3/0x4c0 drivers/net/wireguard/send.c:280
process_one_work+0x3e1/0x950 kernel/workqueue.c:2272
worker_thread+0x635/0xb90 kernel/workqueue.c:2418
kthread+0x1fd/0x220 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read to 0xffffe8ffffc66ef0 of 8 bytes by task 27923 on cpu 1:
dev_fetch_sw_netstats+0xb8/0x160 net/core/dev.c:10357
ip_tunnel_get_stats64+0x38/0x40 net/ipv4/ip_tunnel_core.c:437
dev_get_stats+0x63/0x160 net/core/dev.c:10322
rtnl_fill_stats+0x45/0x320 net/core/rtnetlink.c:1209
rtnl_fill_ifinfo+0xe92/0x2430 net/core/rtnetlink.c:1781
rtmsg_ifinfo_build_skb+0xa2/0x130 net/core/rtnetlink.c:3807
rtmsg_ifinfo_event net/core/rtnetlink.c:3839 [inline]
rtmsg_ifinfo+0x55/0xc0 net/core/rtnetlink.c:3848
__dev_notify_flags+0x63/0x3a0 net/core/dev.c:8457
dev_change_flags+0xa2/0xc0 net/core/dev.c:8499
do_setlink+0x73e/0x21d0 net/core/rtnetlink.c:2706
__rtnl_newlink net/core/rtnetlink.c:3374 [inline]
rtnl_newlink+0xec9/0x13a0 net/core/rtnetlink.c:3500
rtnetlink_rcv_msg+0x723/0x7c0 net/core/rtnetlink.c:5562
netlink_rcv_skb+0x13e/0x240 net/netlink/af_netlink.c:2494
rtnetlink_rcv+0x18/0x20 net/core/rtnetlink.c:5580
netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
netlink_unicast+0x5df/0x6b0 net/netlink/af_netlink.c:1330
netlink_sendmsg+0x6f8/0x7c0 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg net/socket.c:671 [inline]
__sys_sendto+0x2ae/0x380 net/socket.c:1992
__do_sys_sendto net/socket.c:2004 [inline]
__se_sys_sendto net/socket.c:2000 [inline]
__x64_sys_sendto+0x74/0x90 net/socket.c:2000
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 27923 Comm: syz-executor.0 Not tainted 5.10.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.