syzbot

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BUG: KCSAN: data-race in ____sys_sendmsg / fasync_insert_entry

read-write to 0xffff88813a64a240 of 4 bytes by task 378 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 0xffff88813a64a240 of 4 bytes by task 363 on cpu 1:
 ____sys_sendmsg+0x245/0x4c0 net/socket.c:2486
 ___sys_sendmsg net/socket.c:2555 [inline]
 __sys_sendmmsg+0x263/0x500 net/socket.c:2641
 __do_sys_sendmmsg net/socket.c:2670 [inline]
 __se_sys_sendmmsg net/socket.c:2667 [inline]
 __x64_sys_sendmmsg+0x57/0x60 net/socket.c:2667
 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 -> 0x00002402

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 363 Comm: syz-executor.1 Not tainted 6.3.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
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