==================================================================
BUG: KCSAN: data-race in fanout_add / packet_setsockopt

read to 0xffff8880a16edaf8 of 8 bytes by task 16689 on cpu 0:
 packet_setsockopt+0x7f9/0x1390 net/packet/af_packet.c:3846
 __sys_setsockopt+0x1ce/0x370 net/socket.c:2084
 __do_sys_setsockopt net/socket.c:2100 [inline]
 __se_sys_setsockopt net/socket.c:2097 [inline]
 __x64_sys_setsockopt+0x70/0x90 net/socket.c:2097
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8880a16edaf8 of 8 bytes by task 16688 on cpu 1:
 fanout_add+0x9dc/0xa70 net/packet/af_packet.c:1722
 packet_setsockopt+0xca8/0x1390 net/packet/af_packet.c:3842
 __sys_setsockopt+0x1ce/0x370 net/socket.c:2084
 __do_sys_setsockopt net/socket.c:2100 [inline]
 __se_sys_setsockopt net/socket.c:2097 [inline]
 __x64_sys_setsockopt+0x70/0x90 net/socket.c:2097
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 16688 Comm: syz-executor.4 Not tainted 5.4.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 16688 Comm: syz-executor.4 Not tainted 5.4.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x11d/0x181 lib/dump_stack.c:118
 panic+0x210/0x640 kernel/panic.c:221
 kcsan_report.cold+0xc/0xd kernel/kcsan/report.c:315
 kcsan_setup_watchpoint+0x3fe/0x460 kernel/kcsan/core.c:423
 check_access kernel/kcsan/core.c:466 [inline]
 __tsan_write8 kernel/kcsan/core.c:596 [inline]
 __tsan_unaligned_write8+0xc4/0x100 kernel/kcsan/core.c:596
 fanout_add+0x9dc/0xa70 net/packet/af_packet.c:1722
 packet_setsockopt+0xca8/0x1390 net/packet/af_packet.c:3842
 __sys_setsockopt+0x1ce/0x370 net/socket.c:2084
 __do_sys_setsockopt net/socket.c:2100 [inline]
 __se_sys_setsockopt net/socket.c:2097 [inline]
 __x64_sys_setsockopt+0x70/0x90 net/socket.c:2097
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45a639
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007faa66be9c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 000000000045a639
RDX: 0000000000000012 RSI: 0000000000000107 RDI: 0000000000000003
RBP: 000000000075bfc8 R08: 0000000000000004 R09: 0000000000000000
R10: 0000000020000080 R11: 0000000000000246 R12: 00007faa66bea6d4
R13: 00000000004c9705 R14: 00000000004e0e78 R15: 00000000ffffffff
Kernel Offset: disabled
Rebooting in 86400 seconds..