==================================================================
BUG: KCSAN: data-race in inet_send_prepare / mptcp_stream_connect

write to 0xffff888027c1478e of 2 bytes by task 7885 on cpu 1:
 mptcp_copy_inaddrs net/mptcp/protocol.c:2019 [inline]
 mptcp_stream_connect+0x3b0/0x560 net/mptcp/protocol.c:2549
 __sys_connect_file net/socket.c:1852 [inline]
 __sys_connect+0x245/0x280 net/socket.c:1869
 __do_sys_connect net/socket.c:1879 [inline]
 __se_sys_connect net/socket.c:1876 [inline]
 __x64_sys_connect+0x3d/0x50 net/socket.c:1876
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888027c1478e of 2 bytes by task 7915 on cpu 0:
 inet_send_prepare+0x21/0x210 net/ipv4/af_inet.c:802
 inet6_sendmsg+0x29/0x80 net/ipv6/af_inet6.c:635
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg net/socket.c:671 [inline]
 sock_write_iter+0x1a4/0x200 net/socket.c:998
 call_write_iter include/linux/fs.h:1887 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x617/0x690 fs/read_write.c:605
 ksys_write+0xce/0x180 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 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: 7915 Comm: syz-executor.2 Not tainted 5.10.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================