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BUG: KCSAN: data-race in inet_send_prepare / sctp_get_port_local

write to 0xffff888121c6b88e of 2 bytes by task 23875 on cpu 1:
 sctp_get_port_local+0x760/0xaa0 net/sctp/socket.c:8202
 sctp_do_bind+0x38d/0x4a0 net/sctp/socket.c:417
 sctp_autobind net/sctp/socket.c:8481 [inline]
 sctp_connect_new_asoc+0x147/0x390 net/sctp/socket.c:1065
 sctp_sendmsg_new_asoc net/sctp/socket.c:1676 [inline]
 sctp_sendmsg+0x10f5/0x1a90 net/sctp/socket.c:1986
 inet_sendmsg+0x5f/0x80 net/ipv4/af_inet.c:817
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg net/socket.c:671 [inline]
 __sys_sendto+0x2ae/0x380 net/socket.c:1992
 __do_sys_sendto net/socket.c:2004 [inline]
 __se_sys_sendto net/socket.c:2000 [inline]
 __x64_sys_sendto+0x74/0x90 net/socket.c:2000
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888121c6b88e of 2 bytes by task 23881 on cpu 0:
 inet_send_prepare+0x21/0x210 net/ipv4/af_inet.c:802
 inet_sendmsg+0x29/0x80 net/ipv4/af_inet.c:814
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg net/socket.c:671 [inline]
 __sys_sendto+0x2ae/0x380 net/socket.c:1992
 __do_sys_sendto net/socket.c:2004 [inline]
 __se_sys_sendto net/socket.c:2000 [inline]
 __x64_sys_sendto+0x74/0x90 net/socket.c:2000
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 23881 Comm: syz-executor.4 Not tainted 5.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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