netdev - Re: WARNING: possible recursive locking detected

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Date:   Wed, 11 Apr 2018 16:05:35 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+3c43eecd7745a5ce1640@...kaller.appspotmail.com>
Cc:     Christian Brauner <christian.brauner@...ntu.com>,
        David Miller <davem@...emloft.net>,
        David Ahern <dsahern@...il.com>,
        Florian Westphal <fw@...len.de>, Jiri Benc <jbenc@...hat.com>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Xin Long <lucien.xin@...il.com>,
        netdev <netdev@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: WARNING: possible recursive locking detected

On Wed, Apr 11, 2018 at 4:02 PM, syzbot
<syzbot+3c43eecd7745a5ce1640@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzbot hit the following crash on upstream commit
> b284d4d5a6785f8cd07eda2646a95782373cd01e (Tue Apr 10 19:25:30 2018 +0000)
> Merge tag 'ceph-for-4.17-rc1' of git://github.com/ceph/ceph-client
> syzbot dashboard link:
> https://syzkaller.appspot.com/bug?extid=3c43eecd7745a5ce1640
>
> So far this crash happened 3 times on upstream.
> C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5103706542440448
> syzkaller reproducer:
> https://syzkaller.appspot.com/x/repro.syz?id=5641659786199040
> Raw console output:
> https://syzkaller.appspot.com/x/log.txt?id=5099510896263168
> Kernel config:
> https://syzkaller.appspot.com/x/.config?id=-1223000601505858474
> compiler: gcc (GCC) 8.0.1 20180301 (experimental)
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+3c43eecd7745a5ce1640@...kaller.appspotmail.com
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.

#syz dup: possible deadlock in rtnl_lock (5)

> IPVS: sync thread started: state = BACKUP, mcast_ifn = lo, syncid = 0, id =
> 0
> IPVS: stopping backup sync thread 4546 ...
>
> ============================================
> IPVS: stopping backup sync thread 4559 ...
> WARNING: possible recursive locking detected
> 4.16.0+ #19 Not tainted
> --------------------------------------------
> syzkaller046099/4543 is trying to acquire lock:
> 000000008d06d497 (rtnl_mutex){+.+.}, at: rtnl_lock+0x17/0x20
> net/core/rtnetlink.c:74
>
> but task is already holding lock:
> IPVS: stopping backup sync thread 4557 ...
> 000000008d06d497 (rtnl_mutex){+.+.}, at: rtnl_lock+0x17/0x20
> net/core/rtnetlink.c:74
>
> other info that might help us debug this:
>  Possible unsafe locking scenario:
>
>        CPU0
>        ----
>   lock(rtnl_mutex);
>   lock(rtnl_mutex);
>
>  *** DEADLOCK ***
>
>  May be due to missing lock nesting notation
>
> 2 locks held by syzkaller046099/4543:
>  #0: 000000008d06d497 (rtnl_mutex){+.+.}, at: rtnl_lock+0x17/0x20
> net/core/rtnetlink.c:74
>  #1: 000000008326bc5c (ipvs->sync_mutex){+.+.}, at:
> do_ip_vs_set_ctl+0x562/0x1d30 net/netfilter/ipvs/ip_vs_ctl.c:2388
>
> stack backtrace:
> CPU: 1 PID: 4543 Comm: syzkaller046099 Not tainted 4.16.0+ #19
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x1b9/0x294 lib/dump_stack.c:113
>  print_deadlock_bug kernel/locking/lockdep.c:1761 [inline]
>  check_deadlock kernel/locking/lockdep.c:1805 [inline]
>  validate_chain kernel/locking/lockdep.c:2401 [inline]
>  __lock_acquire.cold.62+0x18c/0x55b kernel/locking/lockdep.c:3431
>  lock_acquire+0x1dc/0x520 kernel/locking/lockdep.c:3920
>  __mutex_lock_common kernel/locking/mutex.c:756 [inline]
>  __mutex_lock+0x16d/0x17f0 kernel/locking/mutex.c:893
>  mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>  rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74
>  ip_mc_drop_socket+0x8f/0x270 net/ipv4/igmp.c:2643
>  inet_release+0x4e/0x1f0 net/ipv4/af_inet.c:413
>  sock_release+0x96/0x1b0 net/socket.c:594
>  start_sync_thread+0xdc3/0x2d40 net/netfilter/ipvs/ip_vs_sync.c:1924
>  do_ip_vs_set_ctl+0x59c/0x1d30 net/netfilter/ipvs/ip_vs_ctl.c:2389
>  nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
>  nf_setsockopt+0x7d/0xd0 net/netfilter/nf_sockopt.c:115
>  ip_setsockopt+0xd8/0xf0 net/ipv4/ip_sockglue.c:1253
>  udp_setsockopt+0x62/0xa0 net/ipv4/udp.c:2413
>  ipv6_setsockopt+0x149/0x170 net/ipv6/ipv6_sockglue.c:917
>  udpv6_setsockopt+0x62/0xa0 net/ipv6/udp.c:1424
>  sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:3039
>  __sys_setsockopt+0x1bd/0x390 net/socket.c:1903
>  SYSC_setsockopt net/socket.c:1914 [inline]
>  SyS_setsockopt+0x34/0x50 net/socket.c:1911
>  do_syscall_64+0x29e/0x9d0 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x42/0xb7
> RIP: 0033:0x447c19
> RSP: 002b:00007fb627a93db8 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
> RAX: ffffffffffffffda RBX: 0000000000700024 RCX: 0000000000447c19
> RDX: 000000000000048b RSI: 0000000000000000 RDI: 0000000000000004
> RBP: 0000000000700020 R08: 0000000000000018 R09: 0000000000000000
> R10: 0000000020000100 R11: 0000000000000246 R12: 0000000000000000
> R13: 000000000080fe4f R14: 00007fb627a949c0 R15: 0000000000002710
>
>
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@...glegroups.com.
>
> syzbot will keep track of this bug report.
> If you forgot to add the Reported-by tag, once the fix for this bug is
> merged
> into any tree, please reply to this email with:
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> If you want to test a patch for this bug, please reply with:
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