syzbot

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BUG: KCSAN: data-race in ____sys_recvmsg / fasync_insert_entry

write to 0xffff88810b959540 of 4 bytes by task 6569 on cpu 0:
 fasync_insert_entry+0x137/0x160 fs/fcntl.c:949
 fasync_add_entry fs/fcntl.c:976 [inline]
 fasync_helper+0x59/0xc0 fs/fcntl.c:994
 sock_fasync+0x5c/0xc0 net/socket.c:1283
 ioctl_fioasync fs/ioctl.c:583 [inline]
 do_vfs_ioctl+0x821/0xec0 fs/ioctl.c:686
 __do_sys_ioctl fs/ioctl.c:751 [inline]
 __se_sys_ioctl+0x83/0x140 fs/ioctl.c:739
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:739
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88810b959540 of 4 bytes by task 6616 on cpu 1:
 ____sys_recvmsg+0xcc/0x310 net/socket.c:2563
 ___sys_recvmsg net/socket.c:2611 [inline]
 do_recvmmsg+0x34c/0x9e0 net/socket.c:2705
 __sys_recvmmsg net/socket.c:2784 [inline]
 __do_sys_recvmmsg net/socket.c:2807 [inline]
 __se_sys_recvmmsg net/socket.c:2800 [inline]
 __x64_sys_recvmmsg+0xcf/0x150 net/socket.c:2800
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 6616 Comm: syz-executor.3 Not tainted 5.12.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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