syzbot

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BUG: KCSAN: data-race in do_recvmmsg / unix_dgram_poll

write to 0xffff8881048dac20 of 4 bytes by task 5742 on cpu 0:
 do_recvmmsg+0x653/0x710 net/socket.c:2912
 __sys_recvmmsg net/socket.c:2935 [inline]
 __do_sys_recvmmsg net/socket.c:2958 [inline]
 __se_sys_recvmmsg net/socket.c:2951 [inline]
 __x64_sys_recvmmsg+0xe2/0x160 net/socket.c:2951
 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 0xffff8881048dac20 of 4 bytes by task 5746 on cpu 1:
 unix_dgram_poll+0x72/0x3e0 net/unix/af_unix.c:3211
 sock_poll+0x253/0x270 net/socket.c:1383
 vfs_poll include/linux/poll.h:88 [inline]
 do_pollfd fs/select.c:873 [inline]
 do_poll fs/select.c:921 [inline]
 do_sys_poll+0x630/0xbe0 fs/select.c:1015
 __do_sys_ppoll fs/select.c:1121 [inline]
 __se_sys_ppoll+0x1af/0x1f0 fs/select.c:1101
 __x64_sys_ppoll+0x67/0x80 fs/select.c:1101
 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: 0x00000000 -> 0x0000000e

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 5746 Comm: syz-executor.4 Not tainted 6.3.0-rc4-syzkaller-00195-g5a57b48fdfcb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
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