Re: crypto: deadlock between crypto_alg_sem/rtnl_mutex/genl_mutex

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On Sun, Mar 5, 2017 at 4:08 PM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> 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



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