KCSAN: data-race in inet_send_prepare / mptcp_stream_connect

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: af5043c8 Merge tag 'acpi-5.10-rc4' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10d06baa500000
kernel config: https://syzkaller.appspot.com/x/.config?x=671e27f23e60a67b
dashboard link: https://syzkaller.appspot.com/bug?extid=07a062a4565c7801891e
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [da...@davemloft.net ku...@kernel.org linux-...@vger.kernel.org mathew.j....@linux.intel.com matthie...@tessares.net mp...@lists.01.org net...@vger.kernel.org]

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+07a062...@syzkaller.appspotmail.com

==================================================================
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
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.