From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dmitry Vyukov <dvyukov@google.com>
Subject: Re: crypto: deadlock between crypto_alg_sem/rtnl_mutex/genl_mutex
Date: Tue, 14 Mar 2017 09:14:41 +0100
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 <CACT4Y+bJ1-d3DhCvzEN0PeDd7+P2LNgjF2NHwALXBubOKaOEsw@mail.gmail.com> <CACT4Y+YhLM0CetOZn6uXwyBBGM_oVsW-CC3NMg8A5K0xd3F2mA@mail.gmail.com>
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Cc: syzkaller <syzkaller@googlegroups.com>
To: Herbert Xu <herbert@gondor.apana.org.au>,
        David Miller <davem@davemloft.net>,
        linux-crypto@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        Eric Dumazet <edumazet@google.com>,
        Cong Wang <xiyou.wangcong@gmail.com>,
        netdev <netdev@vger.kernel.org>, santosh.shilimkar@oracle.com,
        rds-devel@oss.oracle.com
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On Mon, Mar 6, 2017 at 10:36 AM, Dmitry Vyukov <dvyukov@google.com> wrote:
> On Sun, Mar 5, 2017 at 6:36 PM, Dmitry Vyukov <dvyukov@google.com> wrote:
>> On Sun, Mar 5, 2017 at 4:08 PM, Dmitry Vyukov <dvyukov@google.com> wrote:
>>> Hello,
>>>
>>> I am getting the following deadlock reports while running syzkaller
>>> fuzzer on net-next/8d70eeb84ab277377c017af6a21d0a337025dede:
>>>
>>> ======================================================
>>> [ INFO: possible circular locking dependency detected ]
>>> 4.10.0+ #5 Not tainted
>>> -------------------------------------------------------
>>> syz-executor6/6143 is trying to acquire lock:
>>>  (nlk->cb_mutex){+.+.+.}, at: [<ffffffff837df634>]
>>> __netlink_dump_start+0xf4/0x760 net/netlink/af_netlink.c:2187
>>>
>>> but task is already holding lock:
>>>  (crypto_alg_sem){+++++.}, at: [<ffffffff821cd1f6>]
>>> crypto_user_rcv_msg+0x136/0x4f0 crypto/crypto_user.c:507
>>>
>>> which lock already depends on the new lock.
>>>
>>>
>>> the existing dependency chain (in reverse order) is:
>>>
>>> -> #4 (crypto_alg_sem){+++++.}:
>>>        validate_chain kernel/locking/lockdep.c:2267 [inline]
>>>        __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>>>        lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>>>        down_read+0x9b/0x150 kernel/locking/rwsem.c:23
>>>        crypto_alg_lookup+0x23/0x50 crypto/api.c:199
>>>        crypto_larval_lookup.part.10+0x9a/0x3b0 crypto/api.c:217
>>>        crypto_larval_lookup crypto/api.c:211 [inline]
>>>        crypto_alg_mod_lookup+0x77/0x1b0 crypto/api.c:270
>>>        crypto_alloc_base+0x50/0x1e0 crypto/api.c:416
>>>        crypto_alloc_cipher include/linux/crypto.h:1407 [inline]
>>>        tcp_fastopen_reset_cipher+0xc2/0x2e0 net/ipv4/tcp_fastopen.c:48
>>>        tcp_fastopen_init_key_once+0x114/0x120 net/ipv4/tcp_fastopen.c:29
>>>        do_tcp_setsockopt.isra.36+0x140a/0x20a0 net/ipv4/tcp.c:2684
>>>        tcp_setsockopt+0xb0/0xd0 net/ipv4/tcp.c:2733
>>>        sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2731
>>>        SYSC_setsockopt net/socket.c:1786 [inline]
>>>        SyS_setsockopt+0x25c/0x390 net/socket.c:1765
>>>        entry_SYSCALL_64_fastpath+0x1f/0xc2
>>>
>>> -> #3 (sk_lock-AF_INET){+.+.+.}:
>>>        validate_chain kernel/locking/lockdep.c:2267 [inline]
>>>        __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>>>        lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>>>        lock_sock_nested+0xcb/0x120 net/core/sock.c:2536
>>>        lock_sock include/net/sock.h:1460 [inline]
>>>        rds_tcp_listen_stop+0x57/0x140 net/rds/tcp_listen.c:284
>>>        rds_tcp_kill_sock net/rds/tcp.c:529 [inline]
>>>        rds_tcp_dev_event+0x383/0xc50 net/rds/tcp.c:568
>>>        notifier_call_chain+0x1b5/0x2b0 kernel/notifier.c:93
>>>        __raw_notifier_call_chain kernel/notifier.c:394 [inline]
>>>        raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401
>>>        call_netdevice_notifiers_info+0x51/0x90 net/core/dev.c:1646
>>>        call_netdevice_notifiers net/core/dev.c:1662 [inline]
>>>        netdev_run_todo+0x3b2/0xa30 net/core/dev.c:7530
>>>        rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:104
>>>        default_device_exit_batch+0x504/0x620 net/core/dev.c:8334
>>>        ops_exit_list.isra.6+0x100/0x150 net/core/net_namespace.c:144
>>>        cleanup_net+0x551/0xa90 net/core/net_namespace.c:463
>>>        process_one_work+0xbd0/0x1c10 kernel/workqueue.c:2096
>>>        worker_thread+0x223/0x1990 kernel/workqueue.c:2230
>>>        kthread+0x326/0x3f0 kernel/kthread.c:229
>>>        ret_from_fork+0x31/0x40 arch/x86/entry/entry_64.S:430
>>>
>>> -> #2 (rtnl_mutex){+.+.+.}:
>>>        validate_chain kernel/locking/lockdep.c:2267 [inline]
>>>        __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>>>        lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>>>        __mutex_lock_common kernel/locking/mutex.c:756 [inline]
>>>        __mutex_lock+0x172/0x1730 kernel/locking/mutex.c:893
>>>        mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>>>        rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
>>>        tipc_nl_bearer_dump+0x3ef/0x720 net/tipc/bearer.c:774
>>>        genl_lock_dumpit+0x68/0x90 net/netlink/genetlink.c:479
>>>        netlink_dump+0x54d/0xd40 net/netlink/af_netlink.c:2127
>>>        __netlink_dump_start+0x4e5/0x760 net/netlink/af_netlink.c:2217
>>>        genl_family_rcv_msg+0xd9d/0x1040 net/netlink/genetlink.c:546
>>>        genl_rcv_msg+0xa6/0x140 net/netlink/genetlink.c:620
>>>        netlink_rcv_skb+0x2ab/0x390 net/netlink/af_netlink.c:2298
>>>        genl_rcv+0x28/0x40 net/netlink/genetlink.c:631
>>>        netlink_unicast_kernel net/netlink/af_netlink.c:1231 [inline]
>>>        netlink_unicast+0x514/0x730 net/netlink/af_netlink.c:1257
>>>        netlink_sendmsg+0xa9f/0xe50 net/netlink/af_netlink.c:1803
>>>        sock_sendmsg_nosec net/socket.c:633 [inline]
>>>        sock_sendmsg+0xca/0x110 net/socket.c:643
>>>        sock_write_iter+0x326/0x600 net/socket.c:846
>>>        call_write_iter include/linux/fs.h:1733 [inline]
>>>        new_sync_write fs/read_write.c:497 [inline]
>>>        __vfs_write+0x483/0x740 fs/read_write.c:510
>>>        vfs_write+0x187/0x530 fs/read_write.c:558
>>>        SYSC_write fs/read_write.c:605 [inline]
>>>        SyS_write+0xfb/0x230 fs/read_write.c:597
>>>        entry_SYSCALL_64_fastpath+0x1f/0xc2
>>>
>>> -> #1 (genl_mutex){+.+.+.}:
>>>        validate_chain kernel/locking/lockdep.c:2267 [inline]
>>>        __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>>>        lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>>>        __mutex_lock_common kernel/locking/mutex.c:756 [inline]
>>>        __mutex_lock+0x172/0x1730 kernel/locking/mutex.c:893
>>>        mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>>>        genl_lock net/netlink/genetlink.c:32 [inline]
>>>        genl_lock_dumpit+0x41/0x90 net/netlink/genetlink.c:478
>>>        netlink_dump+0x54d/0xd40 net/netlink/af_netlink.c:2127
>>>        __netlink_dump_start+0x4e5/0x760 net/netlink/af_netlink.c:2217
>>>        genl_family_rcv_msg+0xd9d/0x1040 net/netlink/genetlink.c:546
>>>        genl_rcv_msg+0xa6/0x140 net/netlink/genetlink.c:620
>>>        netlink_rcv_skb+0x2ab/0x390 net/netlink/af_netlink.c:2298
>>>        genl_rcv+0x28/0x40 net/netlink/genetlink.c:631
>>>        netlink_unicast_kernel net/netlink/af_netlink.c:1231 [inline]
>>>        netlink_unicast+0x514/0x730 net/netlink/af_netlink.c:1257
>>>        netlink_sendmsg+0xa9f/0xe50 net/netlink/af_netlink.c:1803
>>>        sock_sendmsg_nosec net/socket.c:633 [inline]
>>>        sock_sendmsg+0xca/0x110 net/socket.c:643
>>>        sock_write_iter+0x326/0x600 net/socket.c:846
>>>        call_write_iter include/linux/fs.h:1733 [inline]
>>>        new_sync_write fs/read_write.c:497 [inline]
>>>        __vfs_write+0x483/0x740 fs/read_write.c:510
>>>        vfs_write+0x187/0x530 fs/read_write.c:558
>>>        SYSC_write fs/read_write.c:605 [inline]
>>>        SyS_write+0xfb/0x230 fs/read_write.c:597
>>>        entry_SYSCALL_64_fastpath+0x1f/0xc2
>>>
>>> -> #0 (nlk->cb_mutex){+.+.+.}:
>>>        check_prev_add kernel/locking/lockdep.c:1830 [inline]
>>>        check_prevs_add+0xa8f/0x19f0 kernel/locking/lockdep.c:1940
>>>        validate_chain kernel/locking/lockdep.c:2267 [inline]
>>>        __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>>>        lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>>>        __mutex_lock_common kernel/locking/mutex.c:756 [inline]
>>>        __mutex_lock+0x172/0x1730 kernel/locking/mutex.c:893
>>>        mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>>>        __netlink_dump_start+0xf4/0x760 net/netlink/af_netlink.c:2187
>>>        netlink_dump_start include/linux/netlink.h:165 [inline]
>>>        crypto_user_rcv_msg+0x2ad/0x4f0 crypto/crypto_user.c:517
>>>        netlink_rcv_skb+0x2ab/0x390 net/netlink/af_netlink.c:2298
>>>        crypto_netlink_rcv+0x2a/0x40 crypto/crypto_user.c:538
>>>        netlink_unicast_kernel net/netlink/af_netlink.c:1231 [inline]
>>>        netlink_unicast+0x514/0x730 net/netlink/af_netlink.c:1257
>>>        netlink_sendmsg+0xa9f/0xe50 net/netlink/af_netlink.c:1803
>>>        sock_sendmsg_nosec net/socket.c:633 [inline]
>>>        sock_sendmsg+0xca/0x110 net/socket.c:643
>>>        ___sys_sendmsg+0x8fa/0x9f0 net/socket.c:1985
>>>        __sys_sendmsg+0x138/0x300 net/socket.c:2019
>>>        SYSC_sendmsg net/socket.c:2030 [inline]
>>>        SyS_sendmsg+0x2d/0x50 net/socket.c:2026
>>>        entry_SYSCALL_64_fastpath+0x1f/0xc2
>>>
>>> other info that might help us debug this:
>>>
>>> Chain exists of:
>>>   nlk->cb_mutex --> sk_lock-AF_INET --> crypto_alg_sem
>>>
>>>  Possible unsafe locking scenario:
>>>
>>>        CPU0                    CPU1
>>>        ----                    ----
>>>   lock(crypto_alg_sem);
>>>                                lock(sk_lock-AF_INET);
>>>                                lock(crypto_alg_sem);
>>>   lock(nlk->cb_mutex);
>>>
>>>  *** DEADLOCK ***
>>>
>>> 2 locks held by syz-executor6/6143:
>>>  #0:  (crypto_cfg_mutex){+.+...}, at: [<ffffffff821cad9b>]
>>> crypto_netlink_rcv+0x1b/0x40 crypto/crypto_user.c:537
>>>  #1:  (crypto_alg_sem){+++++.}, at: [<ffffffff821cd1f6>]
>>> crypto_user_rcv_msg+0x136/0x4f0 crypto/crypto_user.c:507
>>>
>>> stack backtrace:
>>> CPU: 0 PID: 6143 Comm: syz-executor6 Not tainted 4.10.0+ #5
>>> Hardware name: Google Google Compute Engine/Google Compute Engine,
>>> BIOS Google 01/01/2011
>>> Call Trace:
>>>  __dump_stack lib/dump_stack.c:16 [inline]
>>>  dump_stack+0x2ee/0x3ef lib/dump_stack.c:52
>>>  print_circular_bug+0x307/0x3b0 kernel/locking/lockdep.c:1204
>>>  check_prev_add kernel/locking/lockdep.c:1830 [inline]
>>>  check_prevs_add+0xa8f/0x19f0 kernel/locking/lockdep.c:1940
>>>  validate_chain kernel/locking/lockdep.c:2267 [inline]
>>>  __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>>>  lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>>>  __mutex_lock_common kernel/locking/mutex.c:756 [inline]
>>>  __mutex_lock+0x172/0x1730 kernel/locking/mutex.c:893
>>>  mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>>>  __netlink_dump_start+0xf4/0x760 net/netlink/af_netlink.c:2187
>>>  netlink_dump_start include/linux/netlink.h:165 [inline]
>>>  crypto_user_rcv_msg+0x2ad/0x4f0 crypto/crypto_user.c:517
>>>  netlink_rcv_skb+0x2ab/0x390 net/netlink/af_netlink.c:2298
>>>  crypto_netlink_rcv+0x2a/0x40 crypto/crypto_user.c:538
>>>  netlink_unicast_kernel net/netlink/af_netlink.c:1231 [inline]
>>>  netlink_unicast+0x514/0x730 net/netlink/af_netlink.c:1257
>>>  netlink_sendmsg+0xa9f/0xe50 net/netlink/af_netlink.c:1803
>>>  sock_sendmsg_nosec net/socket.c:633 [inline]
>>>  sock_sendmsg+0xca/0x110 net/socket.c:643
>>>  ___sys_sendmsg+0x8fa/0x9f0 net/socket.c:1985
>>>  __sys_sendmsg+0x138/0x300 net/socket.c:2019
>>>  SYSC_sendmsg net/socket.c:2030 [inline]
>>>  SyS_sendmsg+0x2d/0x50 net/socket.c:2026
>>>  entry_SYSCALL_64_fastpath+0x1f/0xc2
>>
>>
>>
>> Another one involving tcp_md5sig_mutex:
>>
>>
>> ======================================================
>> [ INFO: possible circular locking dependency detected ]
>> SELinux: unrecognized netlink message: protocol=9 nlmsg_type=2
>> sclass=netlink_audit_socket pig=4033 comm=syz-executor4
>> 4.10.0+ #5 Not tainted
>> -------------------------------------------------------
>> syz-executor8/4018 is trying to acquire lock:
>>  (crypto_alg_sem){++++++}, at: [<ffffffff82193473>]
>> crypto_alg_lookup+0x23/0x50 crypto/api.c:199
>>
>> but task is already holding lock:
>>  (tcp_md5sig_mutex){+.+...}, at: [<ffffffff838e4efa>]
>> tcp_alloc_md5sig_pool+0x4a/0x470 net/ipv4/tcp.c:3196
>>
>> which lock already depends on the new lock.
>>
>>
>> the existing dependency chain (in reverse order) is:
>>
>> -> #5 (tcp_md5sig_mutex){+.+...}:
>>        validate_chain kernel/locking/lockdep.c:2267 [inline]
>>        __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>>        lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>>        __mutex_lock_common kernel/locking/mutex.c:756 [inline]
>>        __mutex_lock+0x172/0x1730 kernel/locking/mutex.c:893
>>        mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>>        tcp_alloc_md5sig_pool+0x4a/0x470 net/ipv4/tcp.c:3196
>>        tcp_md5_do_add+0x1d8/0x5d0 net/ipv4/tcp_ipv4.c:969
>>        tcp_v4_parse_md5_keys+0x1c7/0x2b0 net/ipv4/tcp_ipv4.c:1037
>>        do_tcp_setsockopt.isra.36+0x657/0x20a0 net/ipv4/tcp.c:2668
>>        tcp_setsockopt+0xb0/0xd0 net/ipv4/tcp.c:2733
>>        sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2731
>>        SYSC_setsockopt net/socket.c:1786 [inline]
>>        SyS_setsockopt+0x25c/0x390 net/socket.c:1765
>>        do_syscall_64+0x2e8/0x930 arch/x86/entry/common.c:281
>>        return_from_SYSCALL_64+0x0/0x7a
>>
>> -> #4 (sk_lock-AF_INET){+.+.+.}:
>>        validate_chain kernel/locking/lockdep.c:2267 [inline]
>>        __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>>        lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>>        lock_sock_nested+0xcb/0x120 net/core/sock.c:2536
>>        lock_sock include/net/sock.h:1460 [inline]
>>        do_ip_setsockopt.isra.12+0x301/0x3760 net/ipv4/ip_sockglue.c:653
>>        ip_setsockopt+0x3a/0xb0 net/ipv4/ip_sockglue.c:1265
>>        tcp_setsockopt+0x82/0xd0 net/ipv4/tcp.c:2731
>>        sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2731
>>        SYSC_setsockopt net/socket.c:1786 [inline]
>>        SyS_setsockopt+0x25c/0x390 net/socket.c:1765
>>        entry_SYSCALL_64_fastpath+0x1f/0xc2
>>
>> -> #3 (rtnl_mutex){+.+.+.}:
>>        validate_chain kernel/locking/lockdep.c:2267 [inline]
>>        __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>>        lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>>        __mutex_lock_common kernel/locking/mutex.c:756 [inline]
>>        __mutex_lock+0x172/0x1730 kernel/locking/mutex.c:893
>>        mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>>        rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
>>        nl80211_prepare_wdev_dump.isra.37+0x2c/0x5d0 net/wireless/nl80211.c:548
>>        nl80211_dump_station+0x178/0xd80 net/wireless/nl80211.c:4455
>>        genl_lock_dumpit+0x68/0x90 net/netlink/genetlink.c:479
>>        netlink_dump+0x54d/0xd40 net/netlink/af_netlink.c:2127
>>        __netlink_dump_start+0x4e5/0x760 net/netlink/af_netlink.c:2217
>>        genl_family_rcv_msg+0xd9d/0x1040 net/netlink/genetlink.c:546
>>        genl_rcv_msg+0xa6/0x140 net/netlink/genetlink.c:620
>>        netlink_rcv_skb+0x2ab/0x390 net/netlink/af_netlink.c:2298
>>        genl_rcv+0x28/0x40 net/netlink/genetlink.c:631
>>        netlink_unicast_kernel net/netlink/af_netlink.c:1231 [inline]
>>        netlink_unicast+0x514/0x730 net/netlink/af_netlink.c:1257
>>        netlink_sendmsg+0xa9f/0xe50 net/netlink/af_netlink.c:1803
>>        sock_sendmsg_nosec net/socket.c:633 [inline]
>>        sock_sendmsg+0xca/0x110 net/socket.c:643
>>        sock_write_iter+0x326/0x600 net/socket.c:846
>>        call_write_iter include/linux/fs.h:1733 [inline]
>>        new_sync_write fs/read_write.c:497 [inline]
>>        __vfs_write+0x483/0x740 fs/read_write.c:510
>>        vfs_write+0x187/0x530 fs/read_write.c:558
>>        SYSC_write fs/read_write.c:605 [inline]
>>        SyS_write+0xfb/0x230 fs/read_write.c:597
>>        entry_SYSCALL_64_fastpath+0x1f/0xc2
>>
>> -> #2 (genl_mutex){+.+.+.}:
>>        validate_chain kernel/locking/lockdep.c:2267 [inline]
>>        __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>>        lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>>        __mutex_lock_common kernel/locking/mutex.c:756 [inline]
>>        __mutex_lock+0x172/0x1730 kernel/locking/mutex.c:893
>>        mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>>        genl_lock net/netlink/genetlink.c:32 [inline]
>>        genl_lock_dumpit+0x41/0x90 net/netlink/genetlink.c:478
>>        netlink_dump+0x54d/0xd40 net/netlink/af_netlink.c:2127
>>        __netlink_dump_start+0x4e5/0x760 net/netlink/af_netlink.c:2217
>>        genl_family_rcv_msg+0xd9d/0x1040 net/netlink/genetlink.c:546
>>        genl_rcv_msg+0xa6/0x140 net/netlink/genetlink.c:620
>>        netlink_rcv_skb+0x2ab/0x390 net/netlink/af_netlink.c:2298
>>        genl_rcv+0x28/0x40 net/netlink/genetlink.c:631
>>        netlink_unicast_kernel net/netlink/af_netlink.c:1231 [inline]
>>        netlink_unicast+0x514/0x730 net/netlink/af_netlink.c:1257
>>        netlink_sendmsg+0xa9f/0xe50 net/netlink/af_netlink.c:1803
>>        sock_sendmsg_nosec net/socket.c:633 [inline]
>>        sock_sendmsg+0xca/0x110 net/socket.c:643
>>        sock_write_iter+0x326/0x600 net/socket.c:846
>>        call_write_iter include/linux/fs.h:1733 [inline]
>>        new_sync_write fs/read_write.c:497 [inline]
>>        __vfs_write+0x483/0x740 fs/read_write.c:510
>>        vfs_write+0x187/0x530 fs/read_write.c:558
>>        SYSC_write fs/read_write.c:605 [inline]
>>        SyS_write+0xfb/0x230 fs/read_write.c:597
>>        entry_SYSCALL_64_fastpath+0x1f/0xc2
>>
>> -> #1 (nlk->cb_mutex){+.+.+.}:
>>        validate_chain kernel/locking/lockdep.c:2267 [inline]
>>        __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>>        lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>>        __mutex_lock_common kernel/locking/mutex.c:756 [inline]
>>        __mutex_lock+0x172/0x1730 kernel/locking/mutex.c:893
>>        mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>>        __netlink_dump_start+0xf4/0x760 net/netlink/af_netlink.c:2187
>>        netlink_dump_start include/linux/netlink.h:165 [inline]
>>        crypto_user_rcv_msg+0x2ad/0x4f0 crypto/crypto_user.c:517
>>        netlink_rcv_skb+0x2ab/0x390 net/netlink/af_netlink.c:2298
>>        crypto_netlink_rcv+0x2a/0x40 crypto/crypto_user.c:538
>>        netlink_unicast_kernel net/netlink/af_netlink.c:1231 [inline]
>>        netlink_unicast+0x514/0x730 net/netlink/af_netlink.c:1257
>>        netlink_sendmsg+0xa9f/0xe50 net/netlink/af_netlink.c:1803
>>        sock_sendmsg_nosec net/socket.c:633 [inline]
>>        sock_sendmsg+0xca/0x110 net/socket.c:643
>>        ___sys_sendmsg+0x8fa/0x9f0 net/socket.c:1985
>>        __sys_sendmsg+0x138/0x300 net/socket.c:2019
>>        SYSC_sendmsg net/socket.c:2030 [inline]
>>        SyS_sendmsg+0x2d/0x50 net/socket.c:2026
>>        entry_SYSCALL_64_fastpath+0x1f/0xc2
>>
>> -> #0 (crypto_alg_sem){++++++}:
>>        check_prev_add kernel/locking/lockdep.c:1830 [inline]
>>        check_prevs_add+0xa8f/0x19f0 kernel/locking/lockdep.c:1940
>>        validate_chain kernel/locking/lockdep.c:2267 [inline]
>>        __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>>        lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>>        down_read+0x9b/0x150 kernel/locking/rwsem.c:23
>>        crypto_alg_lookup+0x23/0x50 crypto/api.c:199
>>        crypto_larval_lookup.part.10+0x9a/0x3b0 crypto/api.c:217
>>        crypto_larval_lookup crypto/api.c:211 [inline]
>>        crypto_alg_mod_lookup+0x77/0x1b0 crypto/api.c:270
>>        crypto_find_alg crypto/api.c:500 [inline]
>>        crypto_alloc_tfm+0x101/0x2e0 crypto/api.c:533
>>        crypto_alloc_ahash+0x2c/0x40 crypto/ahash.c:525
>>        __tcp_alloc_md5sig_pool net/ipv4/tcp.c:3158 [inline]
>>        tcp_alloc_md5sig_pool+0x85/0x470 net/ipv4/tcp.c:3199
>>        tcp_md5_do_add+0x1d8/0x5d0 net/ipv4/tcp_ipv4.c:969
>>        tcp_v4_parse_md5_keys+0x1c7/0x2b0 net/ipv4/tcp_ipv4.c:1037
>>        do_tcp_setsockopt.isra.36+0x657/0x20a0 net/ipv4/tcp.c:2668
>>        tcp_setsockopt+0xb0/0xd0 net/ipv4/tcp.c:2733
>>        sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2731
>>        SYSC_setsockopt net/socket.c:1786 [inline]
>>        SyS_setsockopt+0x25c/0x390 net/socket.c:1765
>>        do_syscall_64+0x2e8/0x930 arch/x86/entry/common.c:281
>>        return_from_SYSCALL_64+0x0/0x7a
>>
>> other info that might help us debug this:
>>
>> Chain exists of:
>>   crypto_alg_sem --> sk_lock-AF_INET --> tcp_md5sig_mutex
>>
>>  Possible unsafe locking scenario:
>>
>>        CPU0                    CPU1
>>        ----                    ----
>>   lock(tcp_md5sig_mutex);
>>                                lock(sk_lock-AF_INET);
>>                                lock(tcp_md5sig_mutex);
>>   lock(crypto_alg_sem);
>>
>>  *** DEADLOCK ***
>>
>> 2 locks held by syz-executor8/4018:
>>  #0:  (sk_lock-AF_INET){+.+.+.}, at: [<ffffffff838e7a26>] lock_sock
>> include/net/sock.h:1460 [inline]
>>  #0:  (sk_lock-AF_INET){+.+.+.}, at: [<ffffffff838e7a26>]
>> do_tcp_setsockopt.isra.36+0x216/0x20a0 net/ipv4/tcp.c:2466
>>  #1:  (tcp_md5sig_mutex){+.+...}, at: [<ffffffff838e4efa>]
>> tcp_alloc_md5sig_pool+0x4a/0x470 net/ipv4/tcp.c:3196
>>
>> stack backtrace:
>> CPU: 0 PID: 4018 Comm: syz-executor8 Not tainted 4.10.0+ #5
>> Hardware name: Google Google Compute Engine/Google Compute Engine,
>> BIOS Google 01/01/2011
>> Call Trace:
>>  __dump_stack lib/dump_stack.c:16 [inline]
>>  dump_stack+0x2ee/0x3ef lib/dump_stack.c:52
>>  print_circular_bug+0x307/0x3b0 kernel/locking/lockdep.c:1204
>>  check_prev_add kernel/locking/lockdep.c:1830 [inline]
>>  check_prevs_add+0xa8f/0x19f0 kernel/locking/lockdep.c:1940
>>  validate_chain kernel/locking/lockdep.c:2267 [inline]
>>  __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>>  lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>>  down_read+0x9b/0x150 kernel/locking/rwsem.c:23
>>  crypto_alg_lookup+0x23/0x50 crypto/api.c:199
>>  crypto_larval_lookup.part.10+0x9a/0x3b0 crypto/api.c:217
>>  crypto_larval_lookup crypto/api.c:211 [inline]
>>  crypto_alg_mod_lookup+0x77/0x1b0 crypto/api.c:270
>>  crypto_find_alg crypto/api.c:500 [inline]
>>  crypto_alloc_tfm+0x101/0x2e0 crypto/api.c:533
>>  crypto_alloc_ahash+0x2c/0x40 crypto/ahash.c:525
>>  __tcp_alloc_md5sig_pool net/ipv4/tcp.c:3158 [inline]
>>  tcp_alloc_md5sig_pool+0x85/0x470 net/ipv4/tcp.c:3199
>>  tcp_md5_do_add+0x1d8/0x5d0 net/ipv4/tcp_ipv4.c:969
>>  tcp_v4_parse_md5_keys+0x1c7/0x2b0 net/ipv4/tcp_ipv4.c:1037
>>  do_tcp_setsockopt.isra.36+0x657/0x20a0 net/ipv4/tcp.c:2668
>>  tcp_setsockopt+0xb0/0xd0 net/ipv4/tcp.c:2733
>>  sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2731
>>  SYSC_setsockopt net/socket.c:1786 [inline]
>>  SyS_setsockopt+0x25c/0x390 net/socket.c:1765
>>  do_syscall_64+0x2e8/0x930 arch/x86/entry/common.c:281
>
>
>
> Another one:
>
> ======================================================
> [ INFO: possible circular locking dependency detected ]
> 4.10.0+ #6 Not tainted
> -------------------------------------------------------
> syz-executor8/3613 is trying to acquire lock:
>  (sk_lock-AF_INET6){+.+.+.}, at: [<ffffffff83b72eb9>] lock_sock
> include/net/sock.h:1460 [inline]
>  (sk_lock-AF_INET6){+.+.+.}, at: [<ffffffff83b72eb9>]
> do_ipv6_setsockopt.isra.11+0x229/0x36e0 net/ipv6/ipv6_sockglue.c:167
>
> but task is already holding lock:
>  (rtnl_mutex){+.+.+.}, at: [<ffffffff8370a197>] rtnl_lock+0x17/0x20
> net/core/rtnetlink.c:70
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #4 (rtnl_mutex){+.+.+.}:
>        validate_chain kernel/locking/lockdep.c:2267 [inline]
>        __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>        lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>        __mutex_lock_common kernel/locking/mutex.c:756 [inline]
>        __mutex_lock+0x172/0x1730 kernel/locking/mutex.c:893
>        mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>        rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
>        tipc_nl_node_dump_monitor+0x260/0x510 net/tipc/node.c:2128
>        genl_lock_dumpit+0x68/0x90 net/netlink/genetlink.c:479
>        netlink_dump+0x54d/0xd40 net/netlink/af_netlink.c:2127
>        __netlink_dump_start+0x4e5/0x760 net/netlink/af_netlink.c:2217
>        genl_family_rcv_msg+0xd9d/0x1040 net/netlink/genetlink.c:546
>        genl_rcv_msg+0xa6/0x140 net/netlink/genetlink.c:620
>        netlink_rcv_skb+0x2ab/0x390 net/netlink/af_netlink.c:2298
>        genl_rcv+0x28/0x40 net/netlink/genetlink.c:631
>        netlink_unicast_kernel net/netlink/af_netlink.c:1231 [inline]
>        netlink_unicast+0x514/0x730 net/netlink/af_netlink.c:1257
>        netlink_sendmsg+0xa9f/0xe50 net/netlink/af_netlink.c:1803
>        sock_sendmsg_nosec net/socket.c:633 [inline]
>        sock_sendmsg+0xca/0x110 net/socket.c:643
>        sock_write_iter+0x326/0x600 net/socket.c:846
>        call_write_iter include/linux/fs.h:1733 [inline]
>        new_sync_write fs/read_write.c:497 [inline]
>        __vfs_write+0x483/0x740 fs/read_write.c:510
>        vfs_write+0x187/0x530 fs/read_write.c:558
>        SYSC_write fs/read_write.c:605 [inline]
>        SyS_write+0xfb/0x230 fs/read_write.c:597
>        entry_SYSCALL_64_fastpath+0x1f/0xc2
>
> -> #3 (genl_mutex){+.+.+.}:
>        validate_chain kernel/locking/lockdep.c:2267 [inline]
>        __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>        lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>        __mutex_lock_common kernel/locking/mutex.c:756 [inline]
>        __mutex_lock+0x172/0x1730 kernel/locking/mutex.c:893
>        mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>        genl_lock net/netlink/genetlink.c:32 [inline]
>        genl_lock_dumpit+0x41/0x90 net/netlink/genetlink.c:478
>        netlink_dump+0x54d/0xd40 net/netlink/af_netlink.c:2127
>        __netlink_dump_start+0x4e5/0x760 net/netlink/af_netlink.c:2217
>        genl_family_rcv_msg+0xd9d/0x1040 net/netlink/genetlink.c:546
>        genl_rcv_msg+0xa6/0x140 net/netlink/genetlink.c:620
>        netlink_rcv_skb+0x2ab/0x390 net/netlink/af_netlink.c:2298
>        genl_rcv+0x28/0x40 net/netlink/genetlink.c:631
>        netlink_unicast_kernel net/netlink/af_netlink.c:1231 [inline]
>        netlink_unicast+0x514/0x730 net/netlink/af_netlink.c:1257
>        netlink_sendmsg+0xa9f/0xe50 net/netlink/af_netlink.c:1803
>        sock_sendmsg_nosec net/socket.c:633 [inline]
>        sock_sendmsg+0xca/0x110 net/socket.c:643
>        sock_write_iter+0x326/0x600 net/socket.c:846
>        call_write_iter include/linux/fs.h:1733 [inline]
>        new_sync_write fs/read_write.c:497 [inline]
>        __vfs_write+0x483/0x740 fs/read_write.c:510
>        vfs_write+0x187/0x530 fs/read_write.c:558
>        SYSC_write fs/read_write.c:605 [inline]
>        SyS_write+0xfb/0x230 fs/read_write.c:597
>        entry_SYSCALL_64_fastpath+0x1f/0xc2
>
> -> #2 (nlk->cb_mutex){+.+.+.}:
>        validate_chain kernel/locking/lockdep.c:2267 [inline]
>        __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>        lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>        __mutex_lock_common kernel/locking/mutex.c:756 [inline]
>        __mutex_lock+0x172/0x1730 kernel/locking/mutex.c:893
>        mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>        __netlink_dump_start+0xf4/0x760 net/netlink/af_netlink.c:2187
>        netlink_dump_start include/linux/netlink.h:165 [inline]
>        crypto_user_rcv_msg+0x2ad/0x4f0 crypto/crypto_user.c:517
>        netlink_rcv_skb+0x2ab/0x390 net/netlink/af_netlink.c:2298
>        crypto_netlink_rcv+0x2a/0x40 crypto/crypto_user.c:538
>        netlink_unicast_kernel net/netlink/af_netlink.c:1231 [inline]
>        netlink_unicast+0x514/0x730 net/netlink/af_netlink.c:1257
>        netlink_sendmsg+0xa9f/0xe50 net/netlink/af_netlink.c:1803
>        sock_sendmsg_nosec net/socket.c:633 [inline]
>        sock_sendmsg+0xca/0x110 net/socket.c:643
>        ___sys_sendmsg+0x8fa/0x9f0 net/socket.c:1985
>        __sys_sendmsg+0x138/0x300 net/socket.c:2019
>        SYSC_sendmsg net/socket.c:2030 [inline]
>        SyS_sendmsg+0x2d/0x50 net/socket.c:2026
>        entry_SYSCALL_64_fastpath+0x1f/0xc2
>
> -> #1 (crypto_alg_sem){++++++}:
>        validate_chain kernel/locking/lockdep.c:2267 [inline]
>        __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>        lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>        down_read+0x9b/0x150 kernel/locking/rwsem.c:23
>        crypto_alg_lookup+0x23/0x50 crypto/api.c:199
>        crypto_larval_lookup.part.10+0x9a/0x3b0 crypto/api.c:217
>        crypto_larval_lookup crypto/api.c:211 [inline]
>        crypto_alg_mod_lookup+0x77/0x1b0 crypto/api.c:270
>        crypto_find_alg crypto/api.c:500 [inline]
>        crypto_alloc_tfm+0x101/0x2e0 crypto/api.c:533
>        crypto_alloc_shash+0x2c/0x40 crypto/shash.c:433
>        sctp_listen_start net/sctp/socket.c:6969 [inline]
>        sctp_inet_listen+0x5b7/0x7e0 net/sctp/socket.c:7054
>        SYSC_listen net/socket.c:1440 [inline]
>        SyS_listen+0x2c9/0x390 net/socket.c:1426
>        entry_SYSCALL_64_fastpath+0x1f/0xc2
>
> -> #0 (sk_lock-AF_INET6){+.+.+.}:
>        check_prev_add kernel/locking/lockdep.c:1830 [inline]
>        check_prevs_add+0xa8f/0x19f0 kernel/locking/lockdep.c:1940
>        validate_chain kernel/locking/lockdep.c:2267 [inline]
>        __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>        lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>        lock_sock_nested+0xcb/0x120 net/core/sock.c:2536
>        lock_sock include/net/sock.h:1460 [inline]
>        do_ipv6_setsockopt.isra.11+0x229/0x36e0 net/ipv6/ipv6_sockglue.c:167
>        ipv6_setsockopt+0x9b/0x140 net/ipv6/ipv6_sockglue.c:919
>        tcp_setsockopt+0x82/0xd0 net/ipv4/tcp.c:2731
>        sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2731
>        SYSC_setsockopt net/socket.c:1786 [inline]
>        SyS_setsockopt+0x25c/0x390 net/socket.c:1765
>        entry_SYSCALL_64_fastpath+0x1f/0xc2
>
> other info that might help us debug this:
>
> Chain exists of:
>   sk_lock-AF_INET6 --> genl_mutex --> rtnl_mutex
>
>  Possible unsafe locking scenario:
>
>        CPU0                    CPU1
>        ----                    ----
>   lock(rtnl_mutex);
>                                lock(genl_mutex);
>                                lock(rtnl_mutex);
>   lock(sk_lock-AF_INET6);
>
>  *** DEADLOCK ***
>
> 1 lock held by syz-executor8/3613:
>  #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff8370a197>]
> rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
>
> stack backtrace:
> CPU: 1 PID: 3613 Comm: syz-executor8 Not tainted 4.10.0+ #6
> Hardware name: Google Google Compute Engine/Google Compute Engine,
> BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:16 [inline]
>  dump_stack+0x2ee/0x3ef lib/dump_stack.c:52
>  print_circular_bug+0x307/0x3b0 kernel/locking/lockdep.c:1204
>  check_prev_add kernel/locking/lockdep.c:1830 [inline]
>  check_prevs_add+0xa8f/0x19f0 kernel/locking/lockdep.c:1940
>  validate_chain kernel/locking/lockdep.c:2267 [inline]
>  __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
>  lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
>  lock_sock_nested+0xcb/0x120 net/core/sock.c:2536
>  lock_sock include/net/sock.h:1460 [inline]
>  do_ipv6_setsockopt.isra.11+0x229/0x36e0 net/ipv6/ipv6_sockglue.c:167
>  ipv6_setsockopt+0x9b/0x140 net/ipv6/ipv6_sockglue.c:919
>  tcp_setsockopt+0x82/0xd0 net/ipv4/tcp.c:2731
>  sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2731
>  SYSC_setsockopt net/socket.c:1786 [inline]
>  SyS_setsockopt+0x25c/0x390 net/socket.c:1765


Another one now involving rds_tcp_listen_stop (on net-next
3e3eec09311a48c64104cafa193984cc807ab9e0):

[ INFO: possible circular locking dependency detected ]
4.10.0+ #26 Not tainted
-------------------------------------------------------
kworker/u4:1/19 is trying to acquire lock:
 (sk_lock-AF_INET){+.+.+.}, at: [<ffffffff8409a6ec>] lock_sock
include/net/sock.h:1460 [inline]
 (sk_lock-AF_INET){+.+.+.}, at: [<ffffffff8409a6ec>]
rds_tcp_listen_stop+0x5c/0x150 net/rds/tcp_listen.c:288

but task is already holding lock:
 (rtnl_mutex){+.+.+.}, at: [<ffffffff8370b057>] rtnl_lock+0x17/0x20
net/core/rtnetlink.c:70

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (rtnl_mutex){+.+.+.}:
       validate_chain kernel/locking/lockdep.c:2267 [inline]
       __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
       lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
       __mutex_lock_common kernel/locking/mutex.c:756 [inline]
       __mutex_lock+0x172/0x1730 kernel/locking/mutex.c:893
       mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
       rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
       nl80211_prepare_vendor_dump net/wireless/nl80211.c:11511 [inline]
       nl80211_vendor_cmd_dump+0xda/0x1ab0 net/wireless/nl80211.c:11616
       genl_lock_dumpit+0x68/0x90 net/netlink/genetlink.c:479
       netlink_dump+0x54d/0xd40 net/netlink/af_netlink.c:2127
       __netlink_dump_start+0x4e5/0x760 net/netlink/af_netlink.c:2217
       genl_family_rcv_msg+0xd9d/0x1040 net/netlink/genetlink.c:546
       genl_rcv_msg+0xa6/0x140 net/netlink/genetlink.c:620
       netlink_rcv_skb+0x2ab/0x390 net/netlink/af_netlink.c:2298
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:631
       netlink_unicast_kernel net/netlink/af_netlink.c:1231 [inline]
       netlink_unicast+0x514/0x730 net/netlink/af_netlink.c:1257
       netlink_sendmsg+0xa9f/0xe50 net/netlink/af_netlink.c:1803
       sock_sendmsg_nosec net/socket.c:633 [inline]
       sock_sendmsg+0xca/0x110 net/socket.c:643
       ___sys_sendmsg+0x8fa/0x9f0 net/socket.c:1985
       __sys_sendmsg+0x138/0x300 net/socket.c:2019
       SYSC_sendmsg net/socket.c:2030 [inline]
       SyS_sendmsg+0x2d/0x50 net/socket.c:2026
       entry_SYSCALL_64_fastpath+0x1f/0xc2

-> #3 (genl_mutex){+.+.+.}:
       validate_chain kernel/locking/lockdep.c:2267 [inline]
       __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
       lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
       __mutex_lock_common kernel/locking/mutex.c:756 [inline]
       __mutex_lock+0x172/0x1730 kernel/locking/mutex.c:893
       mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
       genl_lock net/netlink/genetlink.c:32 [inline]
       genl_lock_dumpit+0x41/0x90 net/netlink/genetlink.c:478
       netlink_dump+0x54d/0xd40 net/netlink/af_netlink.c:2127
       __netlink_dump_start+0x4e5/0x760 net/netlink/af_netlink.c:2217
       genl_family_rcv_msg+0xd9d/0x1040 net/netlink/genetlink.c:546
       genl_rcv_msg+0xa6/0x140 net/netlink/genetlink.c:620
       netlink_rcv_skb+0x2ab/0x390 net/netlink/af_netlink.c:2298
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:631
       netlink_unicast_kernel net/netlink/af_netlink.c:1231 [inline]
       netlink_unicast+0x514/0x730 net/netlink/af_netlink.c:1257
       netlink_sendmsg+0xa9f/0xe50 net/netlink/af_netlink.c:1803
       sock_sendmsg_nosec net/socket.c:633 [inline]
       sock_sendmsg+0xca/0x110 net/socket.c:643
       ___sys_sendmsg+0x8fa/0x9f0 net/socket.c:1985
       __sys_sendmsg+0x138/0x300 net/socket.c:2019
       SYSC_sendmsg net/socket.c:2030 [inline]
       SyS_sendmsg+0x2d/0x50 net/socket.c:2026
       entry_SYSCALL_64_fastpath+0x1f/0xc2

-> #2 (nlk->cb_mutex){+.+.+.}:
       validate_chain kernel/locking/lockdep.c:2267 [inline]
       __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
       lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
       __mutex_lock_common kernel/locking/mutex.c:756 [inline]
       __mutex_lock+0x172/0x1730 kernel/locking/mutex.c:893
       mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
       __netlink_dump_start+0xf4/0x760 net/netlink/af_netlink.c:2187
       netlink_dump_start include/linux/netlink.h:165 [inline]
       crypto_user_rcv_msg+0x2ad/0x4f0 crypto/crypto_user.c:517
       netlink_rcv_skb+0x2ab/0x390 net/netlink/af_netlink.c:2298
       crypto_netlink_rcv+0x2a/0x40 crypto/crypto_user.c:538
       netlink_unicast_kernel net/netlink/af_netlink.c:1231 [inline]
       netlink_unicast+0x514/0x730 net/netlink/af_netlink.c:1257
       netlink_sendmsg+0xa9f/0xe50 net/netlink/af_netlink.c:1803
       sock_sendmsg_nosec net/socket.c:633 [inline]
       sock_sendmsg+0xca/0x110 net/socket.c:643
       ___sys_sendmsg+0x8fa/0x9f0 net/socket.c:1985
       __sys_sendmsg+0x138/0x300 net/socket.c:2019
       SYSC_sendmsg net/socket.c:2030 [inline]
       SyS_sendmsg+0x2d/0x50 net/socket.c:2026
       entry_SYSCALL_64_fastpath+0x1f/0xc2

-> #1 (crypto_alg_sem){++++++}:
       validate_chain kernel/locking/lockdep.c:2267 [inline]
       __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
       lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
       down_read+0x9b/0x150 kernel/locking/rwsem.c:23
       crypto_alg_lookup+0x23/0x50 crypto/api.c:199
       crypto_larval_lookup.part.10+0x9a/0x3b0 crypto/api.c:217
       crypto_larval_lookup crypto/api.c:211 [inline]
       crypto_alg_mod_lookup+0x77/0x1b0 crypto/api.c:270
       crypto_find_alg crypto/api.c:500 [inline]
       crypto_alloc_tfm+0x101/0x2e0 crypto/api.c:533
       crypto_alloc_shash+0x2c/0x40 crypto/shash.c:433
       sctp_listen_start net/sctp/socket.c:7050 [inline]
       sctp_inet_listen+0x5b7/0x7e0 net/sctp/socket.c:7135
       SYSC_listen net/socket.c:1440 [inline]
       SyS_listen+0x2c9/0x390 net/socket.c:1426
       entry_SYSCALL_64_fastpath+0x1f/0xc2

-> #0 (sk_lock-AF_INET){+.+.+.}:
       check_prev_add kernel/locking/lockdep.c:1830 [inline]
       check_prevs_add+0xa8f/0x19f0 kernel/locking/lockdep.c:1940
       validate_chain kernel/locking/lockdep.c:2267 [inline]
       __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
       lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
       lock_sock_nested+0xcb/0x120 net/core/sock.c:2596
       lock_sock include/net/sock.h:1460 [inline]
       rds_tcp_listen_stop+0x5c/0x150 net/rds/tcp_listen.c:288
       rds_tcp_kill_sock net/rds/tcp.c:532 [inline]
       rds_tcp_dev_event+0x38e/0xc20 net/rds/tcp.c:573
       notifier_call_chain+0x1b5/0x2b0 kernel/notifier.c:93
       __raw_notifier_call_chain kernel/notifier.c:394 [inline]
       raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401
       call_netdevice_notifiers_info+0x51/0x90 net/core/dev.c:1646
       call_netdevice_notifiers net/core/dev.c:1662 [inline]
       netdev_run_todo+0x3b2/0xa30 net/core/dev.c:7530
       rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:104
       default_device_exit_batch+0x504/0x620 net/core/dev.c:8334
       ops_exit_list.isra.6+0x100/0x150 net/core/net_namespace.c:144
       cleanup_net+0x551/0xa90 net/core/net_namespace.c:463
       process_one_work+0xbd0/0x1c10 kernel/workqueue.c:2096
       worker_thread+0x223/0x1990 kernel/workqueue.c:2230
       kthread+0x326/0x3f0 kernel/kthread.c:229
       ret_from_fork+0x31/0x40 arch/x86/entry/entry_64.S:430

other info that might help us debug this:

Chain exists of:
  sk_lock-AF_INET --> genl_mutex --> rtnl_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(rtnl_mutex);
                               lock(genl_mutex);
                               lock(rtnl_mutex);
  lock(sk_lock-AF_INET);

 *** DEADLOCK ***

4 locks held by kworker/u4:1/19:
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff81497943>]
__write_once_size include/linux/compiler.h:283 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff81497943>] atomic64_set
arch/x86/include/asm/atomic64_64.h:33 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff81497943>] atomic_long_set
include/asm-generic/atomic-long.h:56 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff81497943>] set_work_data
kernel/workqueue.c:617 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff81497943>]
set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff81497943>]
process_one_work+0xab3/0x1c10 kernel/workqueue.c:2089
 #1:  (net_cleanup_work){+.+.+.}, at: [<ffffffff81497997>]
process_one_work+0xb07/0x1c10 kernel/workqueue.c:2093
 #2:  (net_mutex){+.+.+.}, at: [<ffffffff836965cb>]
cleanup_net+0x22b/0xa90 net/core/net_namespace.c:429
 #3:  (rtnl_mutex){+.+.+.}, at: [<ffffffff8370b057>]
rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70

stack backtrace:
CPU: 0 PID: 19 Comm: kworker/u4:1 Not tainted 4.10.0+ #26
Hardware name: Google Google Compute Engine/Google Compute Engine,
BIOS Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x2ee/0x3ef lib/dump_stack.c:52
 print_circular_bug+0x307/0x3b0 kernel/locking/lockdep.c:1204
 check_prev_add kernel/locking/lockdep.c:1830 [inline]
 check_prevs_add+0xa8f/0x19f0 kernel/locking/lockdep.c:1940
 validate_chain kernel/locking/lockdep.c:2267 [inline]
 __lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
 lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
 lock_sock_nested+0xcb/0x120 net/core/sock.c:2596
 lock_sock include/net/sock.h:1460 [inline]
 rds_tcp_listen_stop+0x5c/0x150 net/rds/tcp_listen.c:288
 rds_tcp_kill_sock net/rds/tcp.c:532 [inline]
 rds_tcp_dev_event+0x38e/0xc20 net/rds/tcp.c:573
 notifier_call_chain+0x1b5/0x2b0 kernel/notifier.c:93
 __raw_notifier_call_chain kernel/notifier.c:394 [inline]
 raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401
 call_netdevice_notifiers_info+0x51/0x90 net/core/dev.c:1646
 call_netdevice_notifiers net/core/dev.c:1662 [inline]
 netdev_run_todo+0x3b2/0xa30 net/core/dev.c:7530
 rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:104
 default_device_exit_batch+0x504/0x620 net/core/dev.c:8334
 ops_exit_list.isra.6+0x100/0x150 net/core/net_namespace.c:144
 cleanup_net+0x551/0xa90 net/core/net_namespace.c:463
 process_one_work+0xbd0/0x1c10 kernel/workqueue.c:2096
 worker_thread+0x223/0x1990 kernel/workqueue.c:2230
 kthread+0x326/0x3f0 kernel/kthread.c:229
 ret_from_fork+0x31/0x40 arch/x86/entry/entry_64.S:430