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SubjectRe: crypto: deadlock between crypto_alg_sem/rtnl_mutex/genl_mutex
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

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