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

read-write to 0xffff8881038a7a40 of 4 bytes by task 4628 on cpu 0:
 fasync_insert_entry+0x124/0x150 fs/fcntl.c:933
 fasync_add_entry fs/fcntl.c:960 [inline]
 fasync_helper+0x5d/0xc0 fs/fcntl.c:978
 sock_fasync+0x60/0xd0 net/socket.c:1420
 setfl fs/fcntl.c:74 [inline]
 do_fcntl+0xcd2/0xef0 fs/fcntl.c:341
 __do_sys_fcntl fs/fcntl.c:455 [inline]
 __se_sys_fcntl+0xc4/0x180 fs/fcntl.c:440
 __x64_sys_fcntl+0x43/0x50 fs/fcntl.c:440
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff8881038a7a40 of 4 bytes by task 4629 on cpu 1:
 sock_sendpage+0x3e/0xa0 net/socket.c:1076
 pipe_to_sendpage+0x12e/0x160 fs/splice.c:454
 splice_from_pipe_feed fs/splice.c:508 [inline]
 __splice_from_pipe+0x200/0x4a0 fs/splice.c:652
 splice_from_pipe fs/splice.c:687 [inline]
 generic_splice_sendpage+0x9a/0xd0 fs/splice.c:835
 do_splice_from fs/splice.c:856 [inline]
 direct_splice_actor+0x84/0xa0 fs/splice.c:1022
 splice_direct_to_actor+0x2ee/0x5f0 fs/splice.c:977
 do_splice_direct+0x104/0x180 fs/splice.c:1065
 do_sendfile+0x3b8/0x950 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1323 [inline]
 __se_sys_sendfile64 fs/read_write.c:1309 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1309
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x00000002 -> 0x00042802

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 4629 Comm: syz-executor.4 Not tainted 6.3.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
==================================================================