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BUG: KCSAN: data-race in __sys_sendmmsg / smc_switch_to_fallback

write to 0xffff888107b7f9c8 of 8 bytes by task 765 on cpu 1:
 smc_switch_to_fallback+0x453/0x760 net/smc/af_smc.c:924
 smc_sendmsg+0xd6/0x330 net/smc/af_smc.c:2773
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x37c/0x4d0 net/socket.c:2584
 ___sys_sendmsg net/socket.c:2638 [inline]
 __sys_sendmmsg+0x269/0x500 net/socket.c:2724
 __do_sys_sendmmsg net/socket.c:2753 [inline]
 __se_sys_sendmmsg net/socket.c:2750 [inline]
 __x64_sys_sendmmsg+0x57/0x60 net/socket.c:2750
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff888107b7f9c8 of 8 bytes by task 767 on cpu 0:
 sock_from_file net/socket.c:514 [inline]
 sockfd_lookup_light net/socket.c:560 [inline]
 __sys_sendmmsg+0x11f/0x500 net/socket.c:2702
 __do_sys_sendmmsg net/socket.c:2753 [inline]
 __se_sys_sendmmsg net/socket.c:2750 [inline]
 __x64_sys_sendmmsg+0x57/0x60 net/socket.c:2750
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0xffff888123d78680 -> 0xffff888123d7ba80

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 767 Comm: syz-executor.0 Not tainted 6.8.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
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