==================================================================
BUG: KCSAN: data-race in ____sys_sendmsg / fasync_insert_entry

write to 0xffff88811f978240 of 4 bytes by task 16438 on cpu 1:
 fasync_insert_entry+0x12d/0x1b0 fs/fcntl.c:939
 fasync_add_entry fs/fcntl.c:966 [inline]
 fasync_helper+0x79/0xd6 fs/fcntl.c:984
 sock_fasync+0x74/0x100 net/socket.c:1308
 ioctl_fioasync fs/ioctl.c:593 [inline]
 do_vfs_ioctl+0x392/0xd00 fs/ioctl.c:696
 ksys_ioctl+0xb2/0x150 fs/ioctl.c:761
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x47/0x60 fs/ioctl.c:770
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88811f978240 of 4 bytes by task 16434 on cpu 0:
 ____sys_sendmsg+0x16d/0x4c0 net/socket.c:2347
 ___sys_sendmsg+0xb5/0x100 net/socket.c:2416
 __sys_sendmmsg+0x10e/0x310 net/socket.c:2506
 __do_sys_sendmmsg net/socket.c:2535 [inline]
 __se_sys_sendmmsg net/socket.c:2532 [inline]
 __x64_sys_sendmmsg+0x60/0x80 net/socket.c:2532
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 16434 Comm: syz-executor.2 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================