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BUG: KCSAN: data-race in unix_gc / wait_for_unix_gc

write to 0xffffffff8458b113 of 1 bytes by task 976 on cpu 0:
 unix_gc+0x6c/0x8c0 net/unix/garbage.c:216
 unix_release_sock+0x644/0x6f0 net/unix/af_unix.c:591
 unix_release+0x2f/0x50 net/unix/af_unix.c:860
 __sock_release net/socket.c:599 [inline]
 sock_close+0x6c/0x150 net/socket.c:1245
 __fput+0x25b/0x4e0 fs/file_table.c:280
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0xae/0x130 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
 exit_to_user_mode_prepare+0x156/0x190 kernel/entry/common.c:209
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:302
 do_syscall_64+0x56/0x90 arch/x86/entry/common.c:57
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffffffff8458b113 of 1 bytes by task 977 on cpu 1:
 wait_for_unix_gc+0x7c/0x140 net/unix/garbage.c:198
 unix_dgram_sendmsg+0x5f/0x1610 net/unix/af_unix.c:1633
 unix_seqpacket_sendmsg+0xcc/0x110 net/unix/af_unix.c:2056
 sock_sendmsg_nosec net/socket.c:654 [inline]
 sock_sendmsg net/socket.c:674 [inline]
 ____sys_sendmsg+0x360/0x4d0 net/socket.c:2337
 ___sys_sendmsg net/socket.c:2391 [inline]
 __sys_sendmsg+0x1ed/0x270 net/socket.c:2420
 __do_sys_sendmsg net/socket.c:2429 [inline]
 __se_sys_sendmsg net/socket.c:2427 [inline]
 __x64_sys_sendmsg+0x42/0x50 net/socket.c:2427
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 977 Comm: syz-executor.3 Not tainted 5.13.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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