Message-ID: <CACT4Y+aubwO_Xs5viN_P8WzA_WM5Pj7XYVy+M_vxhA7_ZNaz1g@mail.gmail.com>
Date:   Tue, 19 Dec 2017 13:47:00 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot 
        <bot+b17f10c8a8c693b40723d40d6553fbc54d197679@...kaller.appspotmail.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        syzkaller-bugs@...glegroups.com,
        David Miller <davem@...emloft.net>, dsahern@...il.com,
        Florian Westphal <fw@...len.de>,
        Daniel Borkmann <daniel@...earbox.net>,
        Xin Long <lucien.xin@...il.com>, jakub.kicinski@...ronome.com,
        mschiffer@...verse-factory.net,
        Vladislav Yasevich <vyasevich@...il.com>,
        Jiri Benc <jbenc@...hat.com>, netdev <netdev@...r.kernel.org>
Subject: Re: INFO: task hung in cleanup_net

On Tue, Dec 19, 2017 at 1:33 PM, syzbot
<bot+b17f10c8a8c693b40723d40d6553fbc54d197679@...kaller.appspotmail.com>
wrote:
> Hello,
>
> syzkaller hit the following crash on
> e40fd8d6b4d9f59b160faa1736f78fc07533ff37
> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
>
> Unfortunately, I don't have any reproducer for this bug yet.
>
>
> sctp: sctp_transport_update_pmtu: Reported pmtu 508 too low, using default
> minimum of 512
> sctp: sctp_transport_update_pmtu: Reported pmtu 508 too low, using default
> minimum of 512
> sctp: sctp_transport_update_pmtu: Reported pmtu 508 too low, using default
> minimum of 512
> INFO: task kworker/u4:11:3785 blocked for more than 120 seconds.
>       Not tainted 4.15.0-rc2-next-20171207+ #61
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> kworker/u4:11   D16448  3785      2 0x80000000
> Workqueue: netns cleanup_net
> Call Trace:
>  context_switch kernel/sched/core.c:2800 [inline]
>  __schedule+0x8eb/0x2060 kernel/sched/core.c:3376
>  schedule+0xf5/0x430 kernel/sched/core.c:3435
>  schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3493
>  __mutex_lock_common kernel/locking/mutex.c:833 [inline]
>  __mutex_lock+0xaad/0x1a80 kernel/locking/mutex.c:893
>  mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>  rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74
>  cleanup_net+0x24c/0xb60 net/core/net_namespace.c:453
>  process_one_work+0xbfd/0x1bc0 kernel/workqueue.c:2113
>  worker_thread+0x223/0x1990 kernel/workqueue.c:2247
>  kthread+0x37a/0x440 kernel/kthread.c:238
>  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524
>
> Showing all locks held in the system:
> 2 locks held by khungtaskd/672:
>  #0:  (rcu_read_lock){....}, at: [<00000000b9bef8ab>]
> check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
>  #0:  (rcu_read_lock){....}, at: [<00000000b9bef8ab>] watchdog+0x1c5/0xd60
> kernel/hung_task.c:249
>  #1:  (tasklist_lock){.+.+}, at: [<000000006d6acf8b>]
> debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4554
> 1 lock held by rsyslogd/2970:
>  #0:  (&f->f_pos_lock){+.+.}, at: [<000000001cede688>]
> __fdget_pos+0x131/0x1a0 fs/file.c:765
> 2 locks held by getty/3052:
>  #0:  (&tty->ldisc_sem){++++}, at: [<000000004e0245ba>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000ff863b18>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3053:
>  #0:  (&tty->ldisc_sem){++++}, at: [<000000004e0245ba>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000ff863b18>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3054:
>  #0:  (&tty->ldisc_sem){++++}, at: [<000000004e0245ba>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000ff863b18>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3055:
>  #0:  (&tty->ldisc_sem){++++}, at: [<000000004e0245ba>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000ff863b18>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3056:
>  #0:  (&tty->ldisc_sem){++++}, at: [<000000004e0245ba>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000ff863b18>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3057:
>  #0:  (&tty->ldisc_sem){++++}, at: [<000000004e0245ba>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000ff863b18>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3058:
>  #0:  (&tty->ldisc_sem){++++}, at: [<000000004e0245ba>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000ff863b18>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 1 lock held by syz-executor2/3320:
>  #0:  (rtnl_mutex){+.+.}, at: [<0000000063c47ced>] rtnl_lock+0x17/0x20
> net/core/rtnetlink.c:74
> 4 locks held by kworker/u4:11/3785:
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<0000000087d81703>]
> __write_once_size include/linux/compiler.h:212 [inline]
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<0000000087d81703>]
> atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<0000000087d81703>]
> atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<0000000087d81703>]
> set_work_data kernel/workqueue.c:619 [inline]
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<0000000087d81703>]
> set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<0000000087d81703>]
> process_one_work+0xad4/0x1bc0 kernel/workqueue.c:2084
>  #1:  (net_cleanup_work){+.+.}, at: [<000000008a817b5c>]
> process_one_work+0xb2f/0x1bc0 kernel/workqueue.c:2088
>  #2:  (net_mutex){+.+.}, at: [<0000000079150fd8>] cleanup_net+0x247/0xb60
> net/core/net_namespace.c:450
>  #3:  (rtnl_mutex){+.+.}, at: [<0000000063c47ced>] rtnl_lock+0x17/0x20
> net/core/rtnetlink.c:74
> 3 locks held by kworker/0:6/14978:
>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<0000000087d81703>]
> __write_once_size include/linux/compiler.h:212 [inline]
>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<0000000087d81703>]
> atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<0000000087d81703>]
> atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<0000000087d81703>]
> set_work_data kernel/workqueue.c:619 [inline]
>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<0000000087d81703>]
> set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<0000000087d81703>]
> process_one_work+0xad4/0x1bc0 kernel/workqueue.c:2084
>  #1:  ((addr_chk_work).work){+.+.}, at: [<000000008a817b5c>]
> process_one_work+0xb2f/0x1bc0 kernel/workqueue.c:2088
>  #2:  (rtnl_mutex){+.+.}, at: [<0000000063c47ced>] rtnl_lock+0x17/0x20
> net/core/rtnetlink.c:74
> 1 lock held by syz-executor2/15852:
>  #0:  (rtnl_mutex){+.+.}, at: [<0000000063c47ced>] rtnl_lock+0x17/0x20
> net/core/rtnetlink.c:74
> 1 lock held by syz-executor7/15958:
>  #0:  (rtnl_mutex){+.+.}, at: [<0000000063c47ced>] rtnl_lock+0x17/0x20
> net/core/rtnetlink.c:74
> 1 lock held by syz-executor7/15961:
>  #0:  (rtnl_mutex){+.+.}, at: [<0000000063c47ced>] rtnl_lock+0x17/0x20
> net/core/rtnetlink.c:74
>
> =============================================
>
> NMI backtrace for cpu 1
> CPU: 1 PID: 672 Comm: khungtaskd Not tainted 4.15.0-rc2-next-20171207+ #61
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x194/0x257 lib/dump_stack.c:53
>  nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103
>  nmi_trigger_cpumask_backtrace+0x122/0x180 lib/nmi_backtrace.c:62
>  arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
>  trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline]
>  check_hung_task kernel/hung_task.c:132 [inline]
>  check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline]
>  watchdog+0x90c/0xd60 kernel/hung_task.c:249
>  kthread+0x37a/0x440 kernel/kthread.c:238
>  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524
> Sending NMI from CPU 1 to CPUs 0:
> NMI backtrace for cpu 0
> CPU: 0 PID: 15938 Comm: syz-executor7 Not tainted 4.15.0-rc2-next-20171207+
> #61
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:inb arch/x86/include/asm/io.h:348 [inline]
> RIP: 0010:io_serial_in+0x6b/0x90 drivers/tty/serial/8250/8250_port.c:434
> RSP: 0018:ffff8801c1c173e8 EFLAGS: 00000002
> RAX: dffffc0000000000 RBX: 00000000000003fd RCX: 0000000000000000
> RDX: 00000000000003fd RSI: ffffc90001c88000 RDI: ffffffff880fa9c0
> RBP: ffff8801c1c173f8 R08: 0000000000000002 R09: 000000000000000c
> R10: 0000000000000000 R11: ffffffff87896d20 R12: ffffffff880fa980
> R13: 0000000000000020 R14: fffffbfff101f577 R15: fffffbfff101f53a
> FS:  00007f1ef8fad700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fbea91b6000 CR3: 00000001d0aaa000 CR4: 00000000001406f0
> DR0: 0000000020001000 DR1: 0000000020001000 DR2: 0000000020001020
> DR3: 0000000020000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
> Call Trace:
>  serial_in drivers/tty/serial/8250/8250.h:111 [inline]
>  wait_for_xmitr+0x93/0x1e0 drivers/tty/serial/8250/8250_port.c:2033
>  serial8250_console_putchar+0x1f/0x60
> drivers/tty/serial/8250/8250_port.c:3170
>  uart_console_write+0xac/0xe0 drivers/tty/serial/serial_core.c:1858
>  serial8250_console_write+0x647/0xa20
> drivers/tty/serial/8250/8250_port.c:3236
>  univ8250_console_write+0x5f/0x70 drivers/tty/serial/8250/8250_core.c:590
>  call_console_drivers kernel/printk/printk.c:1574 [inline]
>  console_unlock+0x788/0xd70 kernel/printk/printk.c:2233
>  vprintk_emit+0x4ad/0x590 kernel/printk/printk.c:1757
>  vprintk_default+0x28/0x30 kernel/printk/printk.c:1796
>  vprintk_func+0x57/0xc0 kernel/printk/printk_safe.c:379
>  printk+0xaa/0xca kernel/printk/printk.c:1829
>  __dev_set_promiscuity+0x2a4/0x630 net/core/dev.c:6609
>  __dev_change_flags+0x559/0x990 net/core/dev.c:6826
>  dev_change_flags+0x88/0x140 net/core/dev.c:6886
>  dev_ifsioc+0x60d/0x9b0 net/core/dev_ioctl.c:257
>  dev_ioctl+0x2c2/0xf90 net/core/dev_ioctl.c:566
>  sock_do_ioctl+0x94/0xb0 net/socket.c:971
>  sock_ioctl+0x2c2/0x440 net/socket.c:1061
>  vfs_ioctl fs/ioctl.c:46 [inline]
>  do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
>  SYSC_ioctl fs/ioctl.c:701 [inline]
>  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
>  entry_SYSCALL_64_fastpath+0x1f/0x96
> RIP: 0033:0x452a39
> RSP: 002b:00007f1ef8facc58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00007f1ef8fad700 RCX: 0000000000452a39
> RDX: 00000000208a3fe0 RSI: 0000000000008914 RDI: 0000000000000019
> RBP: 0000000000a6f880 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000000
> R13: 0000000000a6f7ff R14: 00007f1ef8fad9c0 R15: 0000000000000002
> Code: 24 d9 00 00 00 49 8d 7c 24 40 48 b8 00 00 00 00 00 fc ff df 48 89 fa
> 48 c1 ea 03 d3 e3 80 3c 02 00 75 17 41 03 5c 24 40 89 da ec <5b> 0f b6 c0 41
> 5c 5d c3 e8 88 ad 18 ff eb c2 e8 e1 ad 18 ff eb


This looks like +rtnetlink issue.

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