syzbot

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BUG: KCSAN: data-race in xprt_connect / xprt_unlock_connect

write to 0xffff8880b8dfccc0 of 8 bytes by task 13811 on cpu 0:
 xprt_unlock_connect+0x5d/0x140 net/sunrpc/xprt.c:811
 xs_tcp_setup_socket+0x737/0x7a0 net/sunrpc/xprtsock.c:2293
 process_one_work+0x3cb/0x990 kernel/workqueue.c:2269
 worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
 kthread+0x210/0x220 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

read to 0xffff8880b8dfccc0 of 8 bytes by task 13893 on cpu 1:
 xprt_release_write net/sunrpc/xprt.c:386 [inline]
 xprt_connect+0x154/0x3f0 net/sunrpc/xprt.c:862
 call_connect+0xfa/0x130 net/sunrpc/clnt.c:2095
 __rpc_execute+0x10e/0x7b0 net/sunrpc/sched.c:913
 rpc_execute+0xc5/0x140 net/sunrpc/sched.c:991
 rpc_run_task+0x395/0x3b0 net/sunrpc/clnt.c:1144
 rpc_call_sync net/sunrpc/clnt.c:1173 [inline]
 rpc_ping net/sunrpc/clnt.c:2735 [inline]
 rpc_create_xprt+0x1c6/0x420 net/sunrpc/clnt.c:481
 rpc_create+0x34c/0x440 net/sunrpc/clnt.c:597
 nfs_create_rpc_client+0x24b/0x2d0 fs/nfs/client.c:535
 nfs_init_client+0x3d/0xa0 fs/nfs/client.c:652
 nfs_get_client+0x856/0x930 fs/nfs/client.c:429
 nfs_init_server fs/nfs/client.c:691 [inline]
 nfs_create_server+0x455/0x1020 fs/nfs/client.c:978
 nfs_try_get_tree+0x19d/0x6c0 fs/nfs/super.c:922
 nfs_get_tree+0xa9f/0xad0 fs/nfs/fs_context.c:1291
 vfs_get_tree+0x4d/0x1a0 fs/super.c:1547
 do_new_mount fs/namespace.c:2874 [inline]
 do_mount+0x115c/0x1bd0 fs/namespace.c:3199
 __do_sys_mount fs/namespace.c:3409 [inline]
 __se_sys_mount+0xd3/0x100 fs/namespace.c:3386
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3386
 do_syscall_64+0x71/0x120 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 13893 Comm: syz-executor.1 Not tainted 5.8.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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