KCSAN: data-race in sctp_assoc_migrate / sctp_hash_obj

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    05f22368 x86, kcsan: Enable KCSAN for x86
git tree:       https://github.com/google/ktsan.git kcsan
console output: https://syzkaller.appspot.com/x/log.txt?x=1046796ce00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=87d111955f40591f
dashboard link: https://syzkaller.appspot.com/bug?extid=e3b35fe7918ff0ee474e
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e3b35fe7918ff0ee474e@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KCSAN: data-race in sctp_assoc_migrate / sctp_hash_obj

write to 0xffff8880b67c0020 of 8 bytes by task 18908 on cpu 1:
 sctp_assoc_migrate+0x1a6/0x290 net/sctp/associola.c:1091
 sctp_sock_migrate+0x8aa/0x9b0 net/sctp/socket.c:9465
 sctp_accept+0x3c8/0x470 net/sctp/socket.c:4916
 inet_accept+0x7f/0x360 net/ipv4/af_inet.c:734
 __sys_accept4+0x224/0x430 net/socket.c:1754
 __do_sys_accept net/socket.c:1795 [inline]
 __se_sys_accept net/socket.c:1792 [inline]
 __x64_sys_accept+0x4e/0x60 net/socket.c:1792
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880b67c0020 of 8 bytes by task 12003 on cpu 0:
 sctp_hash_obj+0x4f/0x2d0 net/sctp/input.c:894
 rht_key_get_hash include/linux/rhashtable.h:133 [inline]
 rht_key_hashfn include/linux/rhashtable.h:159 [inline]
 rht_head_hashfn include/linux/rhashtable.h:174 [inline]
 head_hashfn lib/rhashtable.c:41 [inline]
 rhashtable_rehash_one lib/rhashtable.c:245 [inline]
 rhashtable_rehash_chain lib/rhashtable.c:276 [inline]
 rhashtable_rehash_table lib/rhashtable.c:316 [inline]
 rht_deferred_worker+0x468/0xab0 lib/rhashtable.c:420
 process_one_work+0x3d4/0x890 kernel/workqueue.c:2269
 worker_thread+0xa0/0x800 kernel/workqueue.c:2415
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12003 Comm: kworker/0:6 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: events rht_deferred_worker
==================================================================


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