Re: INFO: task hung in bpf_exit_net

Re: INFO: task hung in bpf_exit_net

[Dmitry Vyukov]

On Tue, Dec 19, 2017 at 1:36 PM, syzbot
<bot+21b498fc12cf2041655f8e1eeae0733807d794b3@syzkaller.appspotmail.com>
wrote:
> Hello,
>
> syzkaller hit the following crash on
> 7ceb97a071e80f1b5e4cd5a36de135612a836388
> 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
> INFO: task kworker/u4:0:5 blocked for more than 120 seconds.
>       Not tainted 4.15.0-rc2-next-20171205+ #59
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> kworker/u4:0    D15808     5      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
>  tc_action_net_exit include/net/act_api.h:125 [inline]
>  bpf_exit_net+0x1a2/0x340 net/sched/act_bpf.c:408
>  ops_exit_list.isra.6+0xae/0x150 net/core/net_namespace.c:142
>  cleanup_net+0x5c7/0xb60 net/core/net_namespace.c:484
>  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:517
>
> Showing all locks held in the system:
> 4 locks held by kworker/u4:0/5:
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
> __write_once_size include/linux/compiler.h:212 [inline]
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
> atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
> atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
> set_work_data kernel/workqueue.c:619 [inline]
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
> set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
> process_one_work+0xad4/0x1bc0 kernel/workqueue.c:2084
>  #1:  (net_cleanup_work){+.+.}, at: [<000000006c7c48a3>]
> process_one_work+0xb2f/0x1bc0 kernel/workqueue.c:2088
>  #2:  (net_mutex){+.+.}, at: [<00000000bf4709f3>] cleanup_net+0x247/0xb60
> net/core/net_namespace.c:450
>  #3:  (rtnl_mutex){+.+.}, at: [<0000000053390f0b>] rtnl_lock+0x17/0x20
> net/core/rtnetlink.c:74
> 3 locks held by kworker/1:0/17:
>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
> __write_once_size include/linux/compiler.h:212 [inline]
>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
> atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
> atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
> set_work_data kernel/workqueue.c:619 [inline]
>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
> set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
> process_one_work+0xad4/0x1bc0 kernel/workqueue.c:2084
>  #1:  ((addr_chk_work).work){+.+.}, at: [<000000006c7c48a3>]
> process_one_work+0xb2f/0x1bc0 kernel/workqueue.c:2088
>  #2:  (rtnl_mutex){+.+.}, at: [<0000000053390f0b>] rtnl_lock+0x17/0x20
> net/core/rtnetlink.c:74
> 2 locks held by khungtaskd/675:
>  #0:  (rcu_read_lock){....}, at: [<00000000587c8471>]
> check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
>  #0:  (rcu_read_lock){....}, at: [<00000000587c8471>] watchdog+0x1c5/0xd60
> kernel/hung_task.c:249
>  #1:  (tasklist_lock){.+.+}, at: [<000000005288685e>]
> debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4554
> 1 lock held by rsyslogd/2974:
>  #0:  (&f->f_pos_lock){+.+.}, at: [<0000000011e00499>]
> __fdget_pos+0x131/0x1a0 fs/file.c:770
> 2 locks held by getty/3056:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3057:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3058:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3059:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3060:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3061:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3062:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>
> =============================================
>
> NMI backtrace for cpu 0
> CPU: 0 PID: 675 Comm: khungtaskd Not tainted 4.15.0-rc2-next-20171205+ #59
> 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:517
> Sending NMI from CPU 0 to CPUs 1:
> NMI backtrace for cpu 1
> CPU: 1 PID: 13156 Comm: syz-executor7 Not tainted 4.15.0-rc2-next-20171205+
> #59
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> task: 000000005209c120 task.stack: 00000000ffaab0e8
> 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:ffff8801c0a16e70 EFLAGS: 00000002
> RAX: dffffc0000000000 RBX: 00000000000003fd RCX: 0000000000000000
> RDX: 00000000000003fd RSI: ffffc90003745000 RDI: ffffffff87cf1a40
> RBP: ffff8801c0a16e80 R08: 0000000000000005 R09: 000000000000000c
> R10: 0000000000000000 R11: ffffffff8748dd20 R12: ffffffff87cf1a00
> R13: 0000000000000020 R14: fffffbfff0f9e387 R15: fffffbfff0f9e34a
> FS:  00007f6d52e3f700(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000c42005de80 CR3: 00000001c368a000 CR4: 00000000001406e0
> DR0: 0000000020000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 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
>  nla_parse+0x374/0x3d0 lib/nlattr.c:257
>  nlmsg_parse include/net/netlink.h:398 [inline]
>  nl80211_dump_wiphy_parse.isra.37.constprop.83+0x138/0x5c0
> net/wireless/nl80211.c:1920
>  nl80211_dump_interface+0x596/0x820 net/wireless/nl80211.c:2660
>  genl_lock_dumpit+0x68/0x90 net/netlink/genetlink.c:480
>  netlink_dump+0x48c/0xce0 net/netlink/af_netlink.c:2186
>  __netlink_dump_start+0x4f0/0x6d0 net/netlink/af_netlink.c:2283
>  genl_family_rcv_msg+0xd27/0xfc0 net/netlink/genetlink.c:548
>  genl_rcv_msg+0xb2/0x140 net/netlink/genetlink.c:624
>  netlink_rcv_skb+0x216/0x440 net/netlink/af_netlink.c:2405
>  genl_rcv+0x28/0x40 net/netlink/genetlink.c:635
>  netlink_unicast_kernel net/netlink/af_netlink.c:1272 [inline]
>  netlink_unicast+0x4e8/0x6f0 net/netlink/af_netlink.c:1298
>  netlink_sendmsg+0xa4a/0xe70 net/netlink/af_netlink.c:1861
>  sock_sendmsg_nosec net/socket.c:636 [inline]
>  sock_sendmsg+0xca/0x110 net/socket.c:646
>  sock_write_iter+0x320/0x5e0 net/socket.c:915
>  call_write_iter include/linux/fs.h:1776 [inline]
>  new_sync_write fs/read_write.c:469 [inline]
>  __vfs_write+0x68a/0x970 fs/read_write.c:482
>  vfs_write+0x18f/0x510 fs/read_write.c:544
>  SYSC_write fs/read_write.c:589 [inline]
>  SyS_write+0xef/0x220 fs/read_write.c:581
>  entry_SYSCALL_64_fastpath+0x1f/0x96
> RIP: 0033:0x4529d9
> RSP: 002b:00007f6d52e3ec58 EFLAGS: 00000212 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 00007f6d52e3f700 RCX: 00000000004529d9
> RDX: 0000000000000024 RSI: 0000000020454000 RDI: 0000000000000016
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000000
> R13: 0000000000a6f7ff R14: 00007f6d52e3f9c0 R15: 0000000000000000
> 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 38 b0 18 ff eb c2 e8 91 b0 18 ff eb
>
>
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@googlegroups.com.
> Please credit me with: Reported-by: syzbot <syzkaller@googlegroups.com>
>
> syzbot will keep track of this bug report.
> Once a fix for this bug is merged into any tree, reply to this email with:
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> To mark this as a duplicate of another syzbot report, please reply with:
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> If it's a one-off invalid bug report, please reply with:
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This looks like +rtnetlink issue.

Re: INFO: task hung in bpf_exit_net

[Xin Long]

On Tue, Dec 19, 2017 at 8:47 PM, Dmitry Vyukov <dvyukov@google.com> wrote:
> On Tue, Dec 19, 2017 at 1:36 PM, syzbot
> <bot+21b498fc12cf2041655f8e1eeae0733807d794b3@syzkaller.appspotmail.com>
> wrote:
>> Hello,
>>
>> syzkaller hit the following crash on
>> 7ceb97a071e80f1b5e4cd5a36de135612a836388
>> 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
>> INFO: task kworker/u4:0:5 blocked for more than 120 seconds.
>>       Not tainted 4.15.0-rc2-next-20171205+ #59
>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>> kworker/u4:0    D15808     5      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
>>  tc_action_net_exit include/net/act_api.h:125 [inline]
>>  bpf_exit_net+0x1a2/0x340 net/sched/act_bpf.c:408
>>  ops_exit_list.isra.6+0xae/0x150 net/core/net_namespace.c:142
>>  cleanup_net+0x5c7/0xb60 net/core/net_namespace.c:484
>>  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:517
>>
[...]
>> 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

I saw this call trace on both 'bpf_exit_net task hung' and
'cleanup_net task hung'.
Note when cpu is here, it's still holding the rtnl_lock in these 2 cases,
one is in nl80211_dump_interface(), and the other one is in dev_ioctl().

I noticed this patch:

commit 54f19b4a679149130f78413c421a5780e90a9d0a
Author: Jiri Olsa <jolsa@kernel.org>
Date:   Wed Sep 21 16:43:15 2016 +0200

    tty/serial/8250: Touch NMI watchdog in wait_for_xmitr

It means in early time, watchdog timeout can be triggered here,
And this patch was to fix it by restarting NMI watchdog timeout
with calling touch_nmi_watchdog().

But this patch missed that it's still holding the rtnl_lock(), other
threads may timeout on watchdog when trying to acquire
rtnl_lock().


>>  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
>>  nla_parse+0x374/0x3d0 lib/nlattr.c:257
>>  nlmsg_parse include/net/netlink.h:398 [inline]
>>  nl80211_dump_wiphy_parse.isra.37.constprop.83+0x138/0x5c0
>> net/wireless/nl80211.c:1920
>>  nl80211_dump_interface+0x596/0x820 net/wireless/nl80211.c:2660
>>  genl_lock_dumpit+0x68/0x90 net/netlink/genetlink.c:480
>>  netlink_dump+0x48c/0xce0 net/netlink/af_netlink.c:2186
>>  __netlink_dump_start+0x4f0/0x6d0 net/netlink/af_netlink.c:2283
>>  genl_family_rcv_msg+0xd27/0xfc0 net/netlink/genetlink.c:548
>>  genl_rcv_msg+0xb2/0x140 net/netlink/genetlink.c:624
>>  netlink_rcv_skb+0x216/0x440 net/netlink/af_netlink.c:2405
>>  genl_rcv+0x28/0x40 net/netlink/genetlink.c:635
>>  netlink_unicast_kernel net/netlink/af_netlink.c:1272 [inline]
>>  netlink_unicast+0x4e8/0x6f0 net/netlink/af_netlink.c:1298
>>  netlink_sendmsg+0xa4a/0xe70 net/netlink/af_netlink.c:1861
>>  sock_sendmsg_nosec net/socket.c:636 [inline]
>>  sock_sendmsg+0xca/0x110 net/socket.c:646
>>  sock_write_iter+0x320/0x5e0 net/socket.c:915
>>  call_write_iter include/linux/fs.h:1776 [inline]
>>  new_sync_write fs/read_write.c:469 [inline]
>>  __vfs_write+0x68a/0x970 fs/read_write.c:482
>>  vfs_write+0x18f/0x510 fs/read_write.c:544
>>  SYSC_write fs/read_write.c:589 [inline]
>>  SyS_write+0xef/0x220 fs/read_write.c:581
>>  entry_SYSCALL_64_fastpath+0x1f/0x96
>> RIP: 0033:0x4529d9
>> RSP: 002b:00007f6d52e3ec58 EFLAGS: 00000212 ORIG_RAX: 0000000000000001
>> RAX: ffffffffffffffda RBX: 00007f6d52e3f700 RCX: 00000000004529d9
>> RDX: 0000000000000024 RSI: 0000000020454000 RDI: 0000000000000016
>> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000000
>> R13: 0000000000a6f7ff R14: 00007f6d52e3f9c0 R15: 0000000000000000
>> 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 38 b0 18 ff eb c2 e8 91 b0 18 ff eb
>>
>>
>> ---
>> This bug is generated by a dumb bot. It may contain errors.
>> See https://goo.gl/tpsmEJ for details.
>> Direct all questions to syzkaller@googlegroups.com.
>> Please credit me with: Reported-by: syzbot <syzkaller@googlegroups.com>
>>
>> syzbot will keep track of this bug report.
>> Once a fix for this bug is merged into any tree, reply to this email with:
>> #syz fix: exact-commit-title
>> To mark this as a duplicate of another syzbot report, please reply with:
>> #syz dup: exact-subject-of-another-report
>> If it's a one-off invalid bug report, please reply with:
>> #syz invalid
>> Note: if the crash happens again, it will cause creation of a new bug
>> report.
>> Note: all commands must start from beginning of the line in the email body.
>>
>> --
>> You received this message because you are subscribed to the Google Groups
>> "syzkaller-bugs" group.
>> To unsubscribe from this group and stop receiving emails from it, send an
>> email to syzkaller-bugs+unsubscribe@googlegroups.com.
>> To view this discussion on the web visit
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>> For more options, visit https://groups.google.com/d/optout.
>
>
> This looks like +rtnetlink issue.

Re: INFO: task hung in bpf_exit_net

[David Ahern]

On 12/19/17 5:47 AM, Dmitry Vyukov wrote:
> On Tue, Dec 19, 2017 at 1:36 PM, syzbot
> <bot+21b498fc12cf2041655f8e1eeae0733807d794b3@syzkaller.appspotmail.com>
> wrote:
>> Hello,
>>
>> syzkaller hit the following crash on
>> 7ceb97a071e80f1b5e4cd5a36de135612a836388
>> 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
>> INFO: task kworker/u4:0:5 blocked for more than 120 seconds.
>>       Not tainted 4.15.0-rc2-next-20171205+ #59
>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>> kworker/u4:0    D15808     5      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
>>  tc_action_net_exit include/net/act_api.h:125 [inline]
>>  bpf_exit_net+0x1a2/0x340 net/sched/act_bpf.c:408
>>  ops_exit_list.isra.6+0xae/0x150 net/core/net_namespace.c:142
>>  cleanup_net+0x5c7/0xb60 net/core/net_namespace.c:484
>>  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:517
>>
>> Showing all locks held in the system:
>> 4 locks held by kworker/u4:0/5:
>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>> __write_once_size include/linux/compiler.h:212 [inline]
>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>> atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>> atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>> set_work_data kernel/workqueue.c:619 [inline]
>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>> set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>> process_one_work+0xad4/0x1bc0 kernel/workqueue.c:2084
>>  #1:  (net_cleanup_work){+.+.}, at: [<000000006c7c48a3>]
>> process_one_work+0xb2f/0x1bc0 kernel/workqueue.c:2088
>>  #2:  (net_mutex){+.+.}, at: [<00000000bf4709f3>] cleanup_net+0x247/0xb60
>> net/core/net_namespace.c:450
>>  #3:  (rtnl_mutex){+.+.}, at: [<0000000053390f0b>] rtnl_lock+0x17/0x20
>> net/core/rtnetlink.c:74
>> 3 locks held by kworker/1:0/17:
>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>> __write_once_size include/linux/compiler.h:212 [inline]
>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>> atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>> atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>> set_work_data kernel/workqueue.c:619 [inline]
>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>> set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>> process_one_work+0xad4/0x1bc0 kernel/workqueue.c:2084
>>  #1:  ((addr_chk_work).work){+.+.}, at: [<000000006c7c48a3>]
>> process_one_work+0xb2f/0x1bc0 kernel/workqueue.c:2088
>>  #2:  (rtnl_mutex){+.+.}, at: [<0000000053390f0b>] rtnl_lock+0x17/0x20
>> net/core/rtnetlink.c:74
>> 2 locks held by khungtaskd/675:
>>  #0:  (rcu_read_lock){....}, at: [<00000000587c8471>]
>> check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
>>  #0:  (rcu_read_lock){....}, at: [<00000000587c8471>] watchdog+0x1c5/0xd60
>> kernel/hung_task.c:249
>>  #1:  (tasklist_lock){.+.+}, at: [<000000005288685e>]
>> debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4554
>> 1 lock held by rsyslogd/2974:
>>  #0:  (&f->f_pos_lock){+.+.}, at: [<0000000011e00499>]
>> __fdget_pos+0x131/0x1a0 fs/file.c:770
>> 2 locks held by getty/3056:
>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>> 2 locks held by getty/3057:
>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>> 2 locks held by getty/3058:
>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>> 2 locks held by getty/3059:
>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>> 2 locks held by getty/3060:
>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>> 2 locks held by getty/3061:
>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>> 2 locks held by getty/3062:
>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>>
>> =============================================
>>
>> NMI backtrace for cpu 0
>> CPU: 0 PID: 675 Comm: khungtaskd Not tainted 4.15.0-rc2-next-20171205+ #59
>> 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:517
>> Sending NMI from CPU 0 to CPUs 1:
>> NMI backtrace for cpu 1
>> CPU: 1 PID: 13156 Comm: syz-executor7 Not tainted 4.15.0-rc2-next-20171205+
>> #59
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>> Google 01/01/2011
>> task: 000000005209c120 task.stack: 00000000ffaab0e8
>> 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:ffff8801c0a16e70 EFLAGS: 00000002
>> RAX: dffffc0000000000 RBX: 00000000000003fd RCX: 0000000000000000
>> RDX: 00000000000003fd RSI: ffffc90003745000 RDI: ffffffff87cf1a40
>> RBP: ffff8801c0a16e80 R08: 0000000000000005 R09: 000000000000000c
>> R10: 0000000000000000 R11: ffffffff8748dd20 R12: ffffffff87cf1a00
>> R13: 0000000000000020 R14: fffffbfff0f9e387 R15: fffffbfff0f9e34a
>> FS:  00007f6d52e3f700(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 000000c42005de80 CR3: 00000001c368a000 CR4: 00000000001406e0
>> DR0: 0000000020000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 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
>>  nla_parse+0x374/0x3d0 lib/nlattr.c:257
>>  nlmsg_parse include/net/netlink.h:398 [inline]
>>  nl80211_dump_wiphy_parse.isra.37.constprop.83+0x138/0x5c0
>> net/wireless/nl80211.c:1920
>>  nl80211_dump_interface+0x596/0x820 net/wireless/nl80211.c:2660
>>  genl_lock_dumpit+0x68/0x90 net/netlink/genetlink.c:480
>>  netlink_dump+0x48c/0xce0 net/netlink/af_netlink.c:2186
>>  __netlink_dump_start+0x4f0/0x6d0 net/netlink/af_netlink.c:2283
>>  genl_family_rcv_msg+0xd27/0xfc0 net/netlink/genetlink.c:548
>>  genl_rcv_msg+0xb2/0x140 net/netlink/genetlink.c:624
>>  netlink_rcv_skb+0x216/0x440 net/netlink/af_netlink.c:2405
>>  genl_rcv+0x28/0x40 net/netlink/genetlink.c:635
>>  netlink_unicast_kernel net/netlink/af_netlink.c:1272 [inline]
>>  netlink_unicast+0x4e8/0x6f0 net/netlink/af_netlink.c:1298
>>  netlink_sendmsg+0xa4a/0xe70 net/netlink/af_netlink.c:1861
>>  sock_sendmsg_nosec net/socket.c:636 [inline]
>>  sock_sendmsg+0xca/0x110 net/socket.c:646
>>  sock_write_iter+0x320/0x5e0 net/socket.c:915
>>  call_write_iter include/linux/fs.h:1776 [inline]
>>  new_sync_write fs/read_write.c:469 [inline]
>>  __vfs_write+0x68a/0x970 fs/read_write.c:482
>>  vfs_write+0x18f/0x510 fs/read_write.c:544
>>  SYSC_write fs/read_write.c:589 [inline]
>>  SyS_write+0xef/0x220 fs/read_write.c:581
>>  entry_SYSCALL_64_fastpath+0x1f/0x96
>> RIP: 0033:0x4529d9
>> RSP: 002b:00007f6d52e3ec58 EFLAGS: 00000212 ORIG_RAX: 0000000000000001
>> RAX: ffffffffffffffda RBX: 00007f6d52e3f700 RCX: 00000000004529d9
>> RDX: 0000000000000024 RSI: 0000000020454000 RDI: 0000000000000016
>> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000000
>> R13: 0000000000a6f7ff R14: 00007f6d52e3f9c0 R15: 0000000000000000
>> 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 38 b0 18 ff eb c2 e8 91 b0 18 ff eb
>>
>>
>> ---
>> This bug is generated by a dumb bot. It may contain errors.
>> See https://goo.gl/tpsmEJ for details.
>> Direct all questions to syzkaller@googlegroups.com.
>> Please credit me with: Reported-by: syzbot <syzkaller@googlegroups.com>
>>
>> syzbot will keep track of this bug report.
>> Once a fix for this bug is merged into any tree, reply to this email with:
>> #syz fix: exact-commit-title
>> To mark this as a duplicate of another syzbot report, please reply with:
>> #syz dup: exact-subject-of-another-report
>> If it's a one-off invalid bug report, please reply with:
>> #syz invalid
>> Note: if the crash happens again, it will cause creation of a new bug
>> report.
>> Note: all commands must start from beginning of the line in the email body.
>>
>> --
>> You received this message because you are subscribed to the Google Groups
>> "syzkaller-bugs" group.
>> To unsubscribe from this group and stop receiving emails from it, send an
>> email to syzkaller-bugs+unsubscribe@googlegroups.com.
>> To view this discussion on the web visit
>> https://groups.google.com/d/msgid/syzkaller-bugs/001a1143fd00a8cc790560b0b552%40google.com.
>> For more options, visit https://groups.google.com/d/optout.
> 
> 
> This looks like +rtnetlink issue.
> 

Same with this one, perhaps related to / fixed by:
    http://patchwork.ozlabs.org/patch/850957/

Re: INFO: task hung in bpf_exit_net

[Dmitry Vyukov]

On Tue, Dec 19, 2017 at 7:20 PM, David Ahern <dsahern@gmail.com> wrote:
> On 12/19/17 5:47 AM, Dmitry Vyukov wrote:
>> On Tue, Dec 19, 2017 at 1:36 PM, syzbot
>> <bot+21b498fc12cf2041655f8e1eeae0733807d794b3@syzkaller.appspotmail.com>
>> wrote:
>>> Hello,
>>>
>>> syzkaller hit the following crash on
>>> 7ceb97a071e80f1b5e4cd5a36de135612a836388
>>> 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
>>> INFO: task kworker/u4:0:5 blocked for more than 120 seconds.
>>>       Not tainted 4.15.0-rc2-next-20171205+ #59
>>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>>> kworker/u4:0    D15808     5      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
>>>  tc_action_net_exit include/net/act_api.h:125 [inline]
>>>  bpf_exit_net+0x1a2/0x340 net/sched/act_bpf.c:408
>>>  ops_exit_list.isra.6+0xae/0x150 net/core/net_namespace.c:142
>>>  cleanup_net+0x5c7/0xb60 net/core/net_namespace.c:484
>>>  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:517
>>>
>>> Showing all locks held in the system:
>>> 4 locks held by kworker/u4:0/5:
>>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>>> __write_once_size include/linux/compiler.h:212 [inline]
>>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>>> atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
>>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>>> atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
>>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>>> set_work_data kernel/workqueue.c:619 [inline]
>>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>>> set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
>>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>>> process_one_work+0xad4/0x1bc0 kernel/workqueue.c:2084
>>>  #1:  (net_cleanup_work){+.+.}, at: [<000000006c7c48a3>]
>>> process_one_work+0xb2f/0x1bc0 kernel/workqueue.c:2088
>>>  #2:  (net_mutex){+.+.}, at: [<00000000bf4709f3>] cleanup_net+0x247/0xb60
>>> net/core/net_namespace.c:450
>>>  #3:  (rtnl_mutex){+.+.}, at: [<0000000053390f0b>] rtnl_lock+0x17/0x20
>>> net/core/rtnetlink.c:74
>>> 3 locks held by kworker/1:0/17:
>>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>>> __write_once_size include/linux/compiler.h:212 [inline]
>>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>>> atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
>>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>>> atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
>>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>>> set_work_data kernel/workqueue.c:619 [inline]
>>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>>> set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
>>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>>> process_one_work+0xad4/0x1bc0 kernel/workqueue.c:2084
>>>  #1:  ((addr_chk_work).work){+.+.}, at: [<000000006c7c48a3>]
>>> process_one_work+0xb2f/0x1bc0 kernel/workqueue.c:2088
>>>  #2:  (rtnl_mutex){+.+.}, at: [<0000000053390f0b>] rtnl_lock+0x17/0x20
>>> net/core/rtnetlink.c:74
>>> 2 locks held by khungtaskd/675:
>>>  #0:  (rcu_read_lock){....}, at: [<00000000587c8471>]
>>> check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
>>>  #0:  (rcu_read_lock){....}, at: [<00000000587c8471>] watchdog+0x1c5/0xd60
>>> kernel/hung_task.c:249
>>>  #1:  (tasklist_lock){.+.+}, at: [<000000005288685e>]
>>> debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4554
>>> 1 lock held by rsyslogd/2974:
>>>  #0:  (&f->f_pos_lock){+.+.}, at: [<0000000011e00499>]
>>> __fdget_pos+0x131/0x1a0 fs/file.c:770
>>> 2 locks held by getty/3056:
>>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>>> 2 locks held by getty/3057:
>>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>>> 2 locks held by getty/3058:
>>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>>> 2 locks held by getty/3059:
>>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>>> 2 locks held by getty/3060:
>>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>>> 2 locks held by getty/3061:
>>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>>> 2 locks held by getty/3062:
>>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>>>
>>> =============================================
>>>
>>> NMI backtrace for cpu 0
>>> CPU: 0 PID: 675 Comm: khungtaskd Not tainted 4.15.0-rc2-next-20171205+ #59
>>> 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:517
>>> Sending NMI from CPU 0 to CPUs 1:
>>> NMI backtrace for cpu 1
>>> CPU: 1 PID: 13156 Comm: syz-executor7 Not tainted 4.15.0-rc2-next-20171205+
>>> #59
>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>>> Google 01/01/2011
>>> task: 000000005209c120 task.stack: 00000000ffaab0e8
>>> 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:ffff8801c0a16e70 EFLAGS: 00000002
>>> RAX: dffffc0000000000 RBX: 00000000000003fd RCX: 0000000000000000
>>> RDX: 00000000000003fd RSI: ffffc90003745000 RDI: ffffffff87cf1a40
>>> RBP: ffff8801c0a16e80 R08: 0000000000000005 R09: 000000000000000c
>>> R10: 0000000000000000 R11: ffffffff8748dd20 R12: ffffffff87cf1a00
>>> R13: 0000000000000020 R14: fffffbfff0f9e387 R15: fffffbfff0f9e34a
>>> FS:  00007f6d52e3f700(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
>>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>> CR2: 000000c42005de80 CR3: 00000001c368a000 CR4: 00000000001406e0
>>> DR0: 0000000020000000 DR1: 0000000000000000 DR2: 0000000000000000
>>> DR3: 0000000000000000 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
>>>  nla_parse+0x374/0x3d0 lib/nlattr.c:257
>>>  nlmsg_parse include/net/netlink.h:398 [inline]
>>>  nl80211_dump_wiphy_parse.isra.37.constprop.83+0x138/0x5c0
>>> net/wireless/nl80211.c:1920
>>>  nl80211_dump_interface+0x596/0x820 net/wireless/nl80211.c:2660
>>>  genl_lock_dumpit+0x68/0x90 net/netlink/genetlink.c:480
>>>  netlink_dump+0x48c/0xce0 net/netlink/af_netlink.c:2186
>>>  __netlink_dump_start+0x4f0/0x6d0 net/netlink/af_netlink.c:2283
>>>  genl_family_rcv_msg+0xd27/0xfc0 net/netlink/genetlink.c:548
>>>  genl_rcv_msg+0xb2/0x140 net/netlink/genetlink.c:624
>>>  netlink_rcv_skb+0x216/0x440 net/netlink/af_netlink.c:2405
>>>  genl_rcv+0x28/0x40 net/netlink/genetlink.c:635
>>>  netlink_unicast_kernel net/netlink/af_netlink.c:1272 [inline]
>>>  netlink_unicast+0x4e8/0x6f0 net/netlink/af_netlink.c:1298
>>>  netlink_sendmsg+0xa4a/0xe70 net/netlink/af_netlink.c:1861
>>>  sock_sendmsg_nosec net/socket.c:636 [inline]
>>>  sock_sendmsg+0xca/0x110 net/socket.c:646
>>>  sock_write_iter+0x320/0x5e0 net/socket.c:915
>>>  call_write_iter include/linux/fs.h:1776 [inline]
>>>  new_sync_write fs/read_write.c:469 [inline]
>>>  __vfs_write+0x68a/0x970 fs/read_write.c:482
>>>  vfs_write+0x18f/0x510 fs/read_write.c:544
>>>  SYSC_write fs/read_write.c:589 [inline]
>>>  SyS_write+0xef/0x220 fs/read_write.c:581
>>>  entry_SYSCALL_64_fastpath+0x1f/0x96
>>> RIP: 0033:0x4529d9
>>> RSP: 002b:00007f6d52e3ec58 EFLAGS: 00000212 ORIG_RAX: 0000000000000001
>>> RAX: ffffffffffffffda RBX: 00007f6d52e3f700 RCX: 00000000004529d9
>>> RDX: 0000000000000024 RSI: 0000000020454000 RDI: 0000000000000016
>>> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
>>> R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000000
>>> R13: 0000000000a6f7ff R14: 00007f6d52e3f9c0 R15: 0000000000000000
>>> 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 38 b0 18 ff eb c2 e8 91 b0 18 ff eb
>>>
>>>
>>> ---
>>> This bug is generated by a dumb bot. It may contain errors.
>>> See https://goo.gl/tpsmEJ for details.
>>> Direct all questions to syzkaller@googlegroups.com.
>>> Please credit me with: Reported-by: syzbot <syzkaller@googlegroups.com>
>>>
>>> syzbot will keep track of this bug report.
>>> Once a fix for this bug is merged into any tree, reply to this email with:
>>> #syz fix: exact-commit-title
>>> To mark this as a duplicate of another syzbot report, please reply with:
>>> #syz dup: exact-subject-of-another-report
>>> If it's a one-off invalid bug report, please reply with:
>>> #syz invalid
>>> Note: if the crash happens again, it will cause creation of a new bug
>>> report.
>>> Note: all commands must start from beginning of the line in the email body.
>>>
>>> --
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>>> "syzkaller-bugs" group.
>>> To unsubscribe from this group and stop receiving emails from it, send an
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>>> To view this discussion on the web visit
>>> https://groups.google.com/d/msgid/syzkaller-bugs/001a1143fd00a8cc790560b0b552%40google.com.
>>> For more options, visit https://groups.google.com/d/optout.
>>
>>
>> This looks like +rtnetlink issue.
>>
>
> Same with this one, perhaps related to / fixed by:
>     http://patchwork.ozlabs.org/patch/850957/
>



Looking at the log, this one seems to be an infinite loop in SCTP code
with console output in it. Kernel is busy printing gazilion of:

[  176.491099] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
low, using default minimum of 512
** 110 printk messages dropped **
[  176.503409] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
low, using default minimum of 512
** 103 printk messages dropped **
...
[  246.742374] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
low, using default minimum of 512
[  246.742484] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
low, using default minimum of 512
[  246.742590] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
low, using default minimum of 512

Looks like a different issue.

Re: INFO: task hung in bpf_exit_net

[Marcelo Ricardo Leitner]

On Fri, Dec 22, 2017 at 11:58:08AM +0100, Dmitry Vyukov wrote:
> On Tue, Dec 19, 2017 at 7:20 PM, David Ahern <dsahern@gmail.com> wrote:
> > On 12/19/17 5:47 AM, Dmitry Vyukov wrote:
> >> On Tue, Dec 19, 2017 at 1:36 PM, syzbot
> >> <bot+21b498fc12cf2041655f8e1eeae0733807d794b3@syzkaller.appspotmail.com>
> >> wrote:
> >>> Hello,
> >>>
> >>> syzkaller hit the following crash on
> >>> 7ceb97a071e80f1b5e4cd5a36de135612a836388
> >>> 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
> >>> INFO: task kworker/u4:0:5 blocked for more than 120 seconds.
> >>>       Not tainted 4.15.0-rc2-next-20171205+ #59
> >>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> >>> kworker/u4:0    D15808     5      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
> >>>  tc_action_net_exit include/net/act_api.h:125 [inline]
> >>>  bpf_exit_net+0x1a2/0x340 net/sched/act_bpf.c:408
> >>>  ops_exit_list.isra.6+0xae/0x150 net/core/net_namespace.c:142
> >>>  cleanup_net+0x5c7/0xb60 net/core/net_namespace.c:484
> >>>  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:517
> >>>
> >>> Showing all locks held in the system:
> >>> 4 locks held by kworker/u4:0/5:
> >>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
> >>> __write_once_size include/linux/compiler.h:212 [inline]
> >>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
> >>> atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
> >>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
> >>> atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
> >>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
> >>> set_work_data kernel/workqueue.c:619 [inline]
> >>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
> >>> set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
> >>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
> >>> process_one_work+0xad4/0x1bc0 kernel/workqueue.c:2084
> >>>  #1:  (net_cleanup_work){+.+.}, at: [<000000006c7c48a3>]
> >>> process_one_work+0xb2f/0x1bc0 kernel/workqueue.c:2088
> >>>  #2:  (net_mutex){+.+.}, at: [<00000000bf4709f3>] cleanup_net+0x247/0xb60
> >>> net/core/net_namespace.c:450
> >>>  #3:  (rtnl_mutex){+.+.}, at: [<0000000053390f0b>] rtnl_lock+0x17/0x20
> >>> net/core/rtnetlink.c:74
> >>> 3 locks held by kworker/1:0/17:
> >>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
> >>> __write_once_size include/linux/compiler.h:212 [inline]
> >>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
> >>> atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
> >>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
> >>> atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
> >>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
> >>> set_work_data kernel/workqueue.c:619 [inline]
> >>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
> >>> set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
> >>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
> >>> process_one_work+0xad4/0x1bc0 kernel/workqueue.c:2084
> >>>  #1:  ((addr_chk_work).work){+.+.}, at: [<000000006c7c48a3>]
> >>> process_one_work+0xb2f/0x1bc0 kernel/workqueue.c:2088
> >>>  #2:  (rtnl_mutex){+.+.}, at: [<0000000053390f0b>] rtnl_lock+0x17/0x20
> >>> net/core/rtnetlink.c:74
> >>> 2 locks held by khungtaskd/675:
> >>>  #0:  (rcu_read_lock){....}, at: [<00000000587c8471>]
> >>> check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
> >>>  #0:  (rcu_read_lock){....}, at: [<00000000587c8471>] watchdog+0x1c5/0xd60
> >>> kernel/hung_task.c:249
> >>>  #1:  (tasklist_lock){.+.+}, at: [<000000005288685e>]
> >>> debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4554
> >>> 1 lock held by rsyslogd/2974:
> >>>  #0:  (&f->f_pos_lock){+.+.}, at: [<0000000011e00499>]
> >>> __fdget_pos+0x131/0x1a0 fs/file.c:770
> >>> 2 locks held by getty/3056:
> >>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
> >>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
> >>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
> >>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> >>> 2 locks held by getty/3057:
> >>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
> >>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
> >>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
> >>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> >>> 2 locks held by getty/3058:
> >>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
> >>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
> >>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
> >>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> >>> 2 locks held by getty/3059:
> >>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
> >>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
> >>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
> >>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> >>> 2 locks held by getty/3060:
> >>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
> >>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
> >>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
> >>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> >>> 2 locks held by getty/3061:
> >>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
> >>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
> >>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
> >>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> >>> 2 locks held by getty/3062:
> >>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
> >>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
> >>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
> >>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> >>>
> >>> =============================================
> >>>
> >>> NMI backtrace for cpu 0
> >>> CPU: 0 PID: 675 Comm: khungtaskd Not tainted 4.15.0-rc2-next-20171205+ #59
> >>> 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:517
> >>> Sending NMI from CPU 0 to CPUs 1:
> >>> NMI backtrace for cpu 1
> >>> CPU: 1 PID: 13156 Comm: syz-executor7 Not tainted 4.15.0-rc2-next-20171205+
> >>> #59
> >>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> >>> Google 01/01/2011
> >>> task: 000000005209c120 task.stack: 00000000ffaab0e8
> >>> 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:ffff8801c0a16e70 EFLAGS: 00000002
> >>> RAX: dffffc0000000000 RBX: 00000000000003fd RCX: 0000000000000000
> >>> RDX: 00000000000003fd RSI: ffffc90003745000 RDI: ffffffff87cf1a40
> >>> RBP: ffff8801c0a16e80 R08: 0000000000000005 R09: 000000000000000c
> >>> R10: 0000000000000000 R11: ffffffff8748dd20 R12: ffffffff87cf1a00
> >>> R13: 0000000000000020 R14: fffffbfff0f9e387 R15: fffffbfff0f9e34a
> >>> FS:  00007f6d52e3f700(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
> >>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >>> CR2: 000000c42005de80 CR3: 00000001c368a000 CR4: 00000000001406e0
> >>> DR0: 0000000020000000 DR1: 0000000000000000 DR2: 0000000000000000
> >>> DR3: 0000000000000000 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
> >>>  nla_parse+0x374/0x3d0 lib/nlattr.c:257
> >>>  nlmsg_parse include/net/netlink.h:398 [inline]
> >>>  nl80211_dump_wiphy_parse.isra.37.constprop.83+0x138/0x5c0
> >>> net/wireless/nl80211.c:1920
> >>>  nl80211_dump_interface+0x596/0x820 net/wireless/nl80211.c:2660
> >>>  genl_lock_dumpit+0x68/0x90 net/netlink/genetlink.c:480
> >>>  netlink_dump+0x48c/0xce0 net/netlink/af_netlink.c:2186
> >>>  __netlink_dump_start+0x4f0/0x6d0 net/netlink/af_netlink.c:2283
> >>>  genl_family_rcv_msg+0xd27/0xfc0 net/netlink/genetlink.c:548
> >>>  genl_rcv_msg+0xb2/0x140 net/netlink/genetlink.c:624
> >>>  netlink_rcv_skb+0x216/0x440 net/netlink/af_netlink.c:2405
> >>>  genl_rcv+0x28/0x40 net/netlink/genetlink.c:635
> >>>  netlink_unicast_kernel net/netlink/af_netlink.c:1272 [inline]
> >>>  netlink_unicast+0x4e8/0x6f0 net/netlink/af_netlink.c:1298
> >>>  netlink_sendmsg+0xa4a/0xe70 net/netlink/af_netlink.c:1861
> >>>  sock_sendmsg_nosec net/socket.c:636 [inline]
> >>>  sock_sendmsg+0xca/0x110 net/socket.c:646
> >>>  sock_write_iter+0x320/0x5e0 net/socket.c:915
> >>>  call_write_iter include/linux/fs.h:1776 [inline]
> >>>  new_sync_write fs/read_write.c:469 [inline]
> >>>  __vfs_write+0x68a/0x970 fs/read_write.c:482
> >>>  vfs_write+0x18f/0x510 fs/read_write.c:544
> >>>  SYSC_write fs/read_write.c:589 [inline]
> >>>  SyS_write+0xef/0x220 fs/read_write.c:581
> >>>  entry_SYSCALL_64_fastpath+0x1f/0x96
> >>> RIP: 0033:0x4529d9
> >>> RSP: 002b:00007f6d52e3ec58 EFLAGS: 00000212 ORIG_RAX: 0000000000000001
> >>> RAX: ffffffffffffffda RBX: 00007f6d52e3f700 RCX: 00000000004529d9
> >>> RDX: 0000000000000024 RSI: 0000000020454000 RDI: 0000000000000016
> >>> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> >>> R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000000
> >>> R13: 0000000000a6f7ff R14: 00007f6d52e3f9c0 R15: 0000000000000000
> >>> 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 38 b0 18 ff eb c2 e8 91 b0 18 ff eb
> >>>
> >>>
> >>> ---
> >>> This bug is generated by a dumb bot. It may contain errors.
> >>> See https://goo.gl/tpsmEJ for details.
> >>> Direct all questions to syzkaller@googlegroups.com.
> >>> Please credit me with: Reported-by: syzbot <syzkaller@googlegroups.com>
> >>>
> >>> syzbot will keep track of this bug report.
> >>> Once a fix for this bug is merged into any tree, reply to this email with:
> >>> #syz fix: exact-commit-title
> >>> To mark this as a duplicate of another syzbot report, please reply with:
> >>> #syz dup: exact-subject-of-another-report
> >>> If it's a one-off invalid bug report, please reply with:
> >>> #syz invalid
> >>> Note: if the crash happens again, it will cause creation of a new bug
> >>> report.
> >>> Note: all commands must start from beginning of the line in the email body.
> >>>
> >>> --
> >>> You received this message because you are subscribed to the Google Groups
> >>> "syzkaller-bugs" group.
> >>> To unsubscribe from this group and stop receiving emails from it, send an
> >>> email to syzkaller-bugs+unsubscribe@googlegroups.com.
> >>> To view this discussion on the web visit
> >>> https://groups.google.com/d/msgid/syzkaller-bugs/001a1143fd00a8cc790560b0b552%40google.com.
> >>> For more options, visit https://groups.google.com/d/optout.
> >>
> >>
> >> This looks like +rtnetlink issue.
> >>
> >
> > Same with this one, perhaps related to / fixed by:
> >     http://patchwork.ozlabs.org/patch/850957/
> >
> 
> 
> 
> Looking at the log, this one seems to be an infinite loop in SCTP code
> with console output in it. Kernel is busy printing gazilion of:

Do you have a link for such log? I don't seem to have received the
initial syzbot email, so I don't have its attachments. Or if you may,
please fwd it to me/list.

Thanks.

> 
> [  176.491099] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> low, using default minimum of 512
> ** 110 printk messages dropped **
> [  176.503409] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> low, using default minimum of 512
> ** 103 printk messages dropped **
> ...
> [  246.742374] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> low, using default minimum of 512
> [  246.742484] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> low, using default minimum of 512
> [  246.742590] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> low, using default minimum of 512
> 
> Looks like a different issue.
> 

Re: INFO: task hung in bpf_exit_net

[Dmitry Vyukov]

On Fri, Dec 22, 2017 at 12:16 PM, Marcelo Ricardo Leitner
<marcelo.leitner@gmail.com> wrote:
> On Fri, Dec 22, 2017 at 11:58:08AM +0100, Dmitry Vyukov wrote:
>> On Tue, Dec 19, 2017 at 7:20 PM, David Ahern <dsahern@gmail.com> wrote:
>> > On 12/19/17 5:47 AM, Dmitry Vyukov wrote:
>> >> On Tue, Dec 19, 2017 at 1:36 PM, syzbot
>> >> <bot+21b498fc12cf2041655f8e1eeae0733807d794b3@syzkaller.appspotmail.com>
>> >> wrote:
>> >>> Hello,
>> >>>
>> >>> syzkaller hit the following crash on
>> >>> 7ceb97a071e80f1b5e4cd5a36de135612a836388
>> >>> 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
>> >>> INFO: task kworker/u4:0:5 blocked for more than 120 seconds.
>> >>>       Not tainted 4.15.0-rc2-next-20171205+ #59
>> >>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>> >>> kworker/u4:0    D15808     5      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
>> >>>  tc_action_net_exit include/net/act_api.h:125 [inline]
>> >>>  bpf_exit_net+0x1a2/0x340 net/sched/act_bpf.c:408
>> >>>  ops_exit_list.isra.6+0xae/0x150 net/core/net_namespace.c:142
>> >>>  cleanup_net+0x5c7/0xb60 net/core/net_namespace.c:484
>> >>>  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:517
>> >>>
>> >>> Showing all locks held in the system:
>> >>> 4 locks held by kworker/u4:0/5:
>> >>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>> >>> __write_once_size include/linux/compiler.h:212 [inline]
>> >>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>> >>> atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
>> >>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>> >>> atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
>> >>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>> >>> set_work_data kernel/workqueue.c:619 [inline]
>> >>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>> >>> set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
>> >>>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000b9f061a2>]
>> >>> process_one_work+0xad4/0x1bc0 kernel/workqueue.c:2084
>> >>>  #1:  (net_cleanup_work){+.+.}, at: [<000000006c7c48a3>]
>> >>> process_one_work+0xb2f/0x1bc0 kernel/workqueue.c:2088
>> >>>  #2:  (net_mutex){+.+.}, at: [<00000000bf4709f3>] cleanup_net+0x247/0xb60
>> >>> net/core/net_namespace.c:450
>> >>>  #3:  (rtnl_mutex){+.+.}, at: [<0000000053390f0b>] rtnl_lock+0x17/0x20
>> >>> net/core/rtnetlink.c:74
>> >>> 3 locks held by kworker/1:0/17:
>> >>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>> >>> __write_once_size include/linux/compiler.h:212 [inline]
>> >>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>> >>> atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
>> >>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>> >>> atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
>> >>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>> >>> set_work_data kernel/workqueue.c:619 [inline]
>> >>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>> >>> set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
>> >>>  #0:  ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000b9f061a2>]
>> >>> process_one_work+0xad4/0x1bc0 kernel/workqueue.c:2084
>> >>>  #1:  ((addr_chk_work).work){+.+.}, at: [<000000006c7c48a3>]
>> >>> process_one_work+0xb2f/0x1bc0 kernel/workqueue.c:2088
>> >>>  #2:  (rtnl_mutex){+.+.}, at: [<0000000053390f0b>] rtnl_lock+0x17/0x20
>> >>> net/core/rtnetlink.c:74
>> >>> 2 locks held by khungtaskd/675:
>> >>>  #0:  (rcu_read_lock){....}, at: [<00000000587c8471>]
>> >>> check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
>> >>>  #0:  (rcu_read_lock){....}, at: [<00000000587c8471>] watchdog+0x1c5/0xd60
>> >>> kernel/hung_task.c:249
>> >>>  #1:  (tasklist_lock){.+.+}, at: [<000000005288685e>]
>> >>> debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4554
>> >>> 1 lock held by rsyslogd/2974:
>> >>>  #0:  (&f->f_pos_lock){+.+.}, at: [<0000000011e00499>]
>> >>> __fdget_pos+0x131/0x1a0 fs/file.c:770
>> >>> 2 locks held by getty/3056:
>> >>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>> >>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>> >>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>> >>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>> >>> 2 locks held by getty/3057:
>> >>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>> >>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>> >>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>> >>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>> >>> 2 locks held by getty/3058:
>> >>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>> >>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>> >>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>> >>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>> >>> 2 locks held by getty/3059:
>> >>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>> >>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>> >>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>> >>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>> >>> 2 locks held by getty/3060:
>> >>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>> >>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>> >>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>> >>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>> >>> 2 locks held by getty/3061:
>> >>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>> >>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>> >>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>> >>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>> >>> 2 locks held by getty/3062:
>> >>>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000b9fd70a9>]
>> >>> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>> >>>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000abb3bd08>]
>> >>> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>> >>>
>> >>> =============================================
>> >>>
>> >>> NMI backtrace for cpu 0
>> >>> CPU: 0 PID: 675 Comm: khungtaskd Not tainted 4.15.0-rc2-next-20171205+ #59
>> >>> 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:517
>> >>> Sending NMI from CPU 0 to CPUs 1:
>> >>> NMI backtrace for cpu 1
>> >>> CPU: 1 PID: 13156 Comm: syz-executor7 Not tainted 4.15.0-rc2-next-20171205+
>> >>> #59
>> >>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>> >>> Google 01/01/2011
>> >>> task: 000000005209c120 task.stack: 00000000ffaab0e8
>> >>> 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:ffff8801c0a16e70 EFLAGS: 00000002
>> >>> RAX: dffffc0000000000 RBX: 00000000000003fd RCX: 0000000000000000
>> >>> RDX: 00000000000003fd RSI: ffffc90003745000 RDI: ffffffff87cf1a40
>> >>> RBP: ffff8801c0a16e80 R08: 0000000000000005 R09: 000000000000000c
>> >>> R10: 0000000000000000 R11: ffffffff8748dd20 R12: ffffffff87cf1a00
>> >>> R13: 0000000000000020 R14: fffffbfff0f9e387 R15: fffffbfff0f9e34a
>> >>> FS:  00007f6d52e3f700(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
>> >>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> >>> CR2: 000000c42005de80 CR3: 00000001c368a000 CR4: 00000000001406e0
>> >>> DR0: 0000000020000000 DR1: 0000000000000000 DR2: 0000000000000000
>> >>> DR3: 0000000000000000 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
>> >>>  nla_parse+0x374/0x3d0 lib/nlattr.c:257
>> >>>  nlmsg_parse include/net/netlink.h:398 [inline]
>> >>>  nl80211_dump_wiphy_parse.isra.37.constprop.83+0x138/0x5c0
>> >>> net/wireless/nl80211.c:1920
>> >>>  nl80211_dump_interface+0x596/0x820 net/wireless/nl80211.c:2660
>> >>>  genl_lock_dumpit+0x68/0x90 net/netlink/genetlink.c:480
>> >>>  netlink_dump+0x48c/0xce0 net/netlink/af_netlink.c:2186
>> >>>  __netlink_dump_start+0x4f0/0x6d0 net/netlink/af_netlink.c:2283
>> >>>  genl_family_rcv_msg+0xd27/0xfc0 net/netlink/genetlink.c:548
>> >>>  genl_rcv_msg+0xb2/0x140 net/netlink/genetlink.c:624
>> >>>  netlink_rcv_skb+0x216/0x440 net/netlink/af_netlink.c:2405
>> >>>  genl_rcv+0x28/0x40 net/netlink/genetlink.c:635
>> >>>  netlink_unicast_kernel net/netlink/af_netlink.c:1272 [inline]
>> >>>  netlink_unicast+0x4e8/0x6f0 net/netlink/af_netlink.c:1298
>> >>>  netlink_sendmsg+0xa4a/0xe70 net/netlink/af_netlink.c:1861
>> >>>  sock_sendmsg_nosec net/socket.c:636 [inline]
>> >>>  sock_sendmsg+0xca/0x110 net/socket.c:646
>> >>>  sock_write_iter+0x320/0x5e0 net/socket.c:915
>> >>>  call_write_iter include/linux/fs.h:1776 [inline]
>> >>>  new_sync_write fs/read_write.c:469 [inline]
>> >>>  __vfs_write+0x68a/0x970 fs/read_write.c:482
>> >>>  vfs_write+0x18f/0x510 fs/read_write.c:544
>> >>>  SYSC_write fs/read_write.c:589 [inline]
>> >>>  SyS_write+0xef/0x220 fs/read_write.c:581
>> >>>  entry_SYSCALL_64_fastpath+0x1f/0x96
>> >>> RIP: 0033:0x4529d9
>> >>> RSP: 002b:00007f6d52e3ec58 EFLAGS: 00000212 ORIG_RAX: 0000000000000001
>> >>> RAX: ffffffffffffffda RBX: 00007f6d52e3f700 RCX: 00000000004529d9
>> >>> RDX: 0000000000000024 RSI: 0000000020454000 RDI: 0000000000000016
>> >>> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
>> >>> R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000000
>> >>> R13: 0000000000a6f7ff R14: 00007f6d52e3f9c0 R15: 0000000000000000
>> >>> 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 38 b0 18 ff eb c2 e8 91 b0 18 ff eb
>> >>>
>> >>>
>> >>> ---
>> >>> This bug is generated by a dumb bot. It may contain errors.
>> >>> See https://goo.gl/tpsmEJ for details.
>> >>> Direct all questions to syzkaller@googlegroups.com.
>> >>> Please credit me with: Reported-by: syzbot <syzkaller@googlegroups.com>
>> >>>
>> >>> syzbot will keep track of this bug report.
>> >>> Once a fix for this bug is merged into any tree, reply to this email with:
>> >>> #syz fix: exact-commit-title
>> >>> To mark this as a duplicate of another syzbot report, please reply with:
>> >>> #syz dup: exact-subject-of-another-report
>> >>> If it's a one-off invalid bug report, please reply with:
>> >>> #syz invalid
>> >>> Note: if the crash happens again, it will cause creation of a new bug
>> >>> report.
>> >>> Note: all commands must start from beginning of the line in the email body.
>> >>>
>> >>> --
>> >>> You received this message because you are subscribed to the Google Groups
>> >>> "syzkaller-bugs" group.
>> >>> To unsubscribe from this group and stop receiving emails from it, send an
>> >>> email to syzkaller-bugs+unsubscribe@googlegroups.com.
>> >>> To view this discussion on the web visit
>> >>> https://groups.google.com/d/msgid/syzkaller-bugs/001a1143fd00a8cc790560b0b552%40google.com.
>> >>> For more options, visit https://groups.google.com/d/optout.
>> >>
>> >>
>> >> This looks like +rtnetlink issue.
>> >>
>> >
>> > Same with this one, perhaps related to / fixed by:
>> >     http://patchwork.ozlabs.org/patch/850957/
>> >
>>
>>
>>
>> Looking at the log, this one seems to be an infinite loop in SCTP code
>> with console output in it. Kernel is busy printing gazilion of:
>
> Do you have a link for such log? I don't seem to have received the
> initial syzbot email, so I don't have its attachments. Or if you may,
> please fwd it to me/list.

https://groups.google.com/forum/#!searchin/syzkaller-bugs/%22INFO$3A$20task$20hung$20in$20bpf_exit_net%22%7Csort:date



> Thanks.
>
>>
>> [  176.491099] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
>> low, using default minimum of 512
>> ** 110 printk messages dropped **
>> [  176.503409] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
>> low, using default minimum of 512
>> ** 103 printk messages dropped **
>> ...
>> [  246.742374] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
>> low, using default minimum of 512
>> [  246.742484] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
>> low, using default minimum of 512
>> [  246.742590] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
>> low, using default minimum of 512
>>
>> Looks like a different issue.
>>

Re: INFO: task hung in bpf_exit_net

[Marcelo Ricardo Leitner]

On Fri, Dec 22, 2017 at 11:58:08AM +0100, Dmitry Vyukov wrote:
...
> > Same with this one, perhaps related to / fixed by:
> >     http://patchwork.ozlabs.org/patch/850957/
> >
> 
> 
> 
> Looking at the log, this one seems to be an infinite loop in SCTP code
> with console output in it. Kernel is busy printing gazilion of:
> 
> [  176.491099] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> low, using default minimum of 512
> ** 110 printk messages dropped **
> [  176.503409] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> low, using default minimum of 512
> ** 103 printk messages dropped **
> ...
> [  246.742374] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> low, using default minimum of 512
> [  246.742484] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> low, using default minimum of 512
> [  246.742590] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> low, using default minimum of 512
> 
> Looks like a different issue.
> 

Oh. I guess this is caused by the interface having a MTU smaller than
SCTP_DEFAULT_MINSEGMENT (512), as the icmp frag needed handler
(sctp_icmp_frag_needed) will trigger an instant retransmission.
But as the MTU is smaller, SCTP won't update it, but will issue the
retransmission anyway.

I will test this soon. Should be fairly easy to trigger it.

  Marcelo

Re: INFO: task hung in bpf_exit_net

[Marcelo Ricardo Leitner]

On Fri, Dec 22, 2017 at 04:28:07PM -0200, Marcelo Ricardo Leitner wrote:
> On Fri, Dec 22, 2017 at 11:58:08AM +0100, Dmitry Vyukov wrote:
> ...
> > > Same with this one, perhaps related to / fixed by:
> > >     http://patchwork.ozlabs.org/patch/850957/
> > >
> > 
> > 
> > 
> > Looking at the log, this one seems to be an infinite loop in SCTP code
> > with console output in it. Kernel is busy printing gazilion of:
> > 
> > [  176.491099] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> > low, using default minimum of 512
> > ** 110 printk messages dropped **
> > [  176.503409] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> > low, using default minimum of 512
> > ** 103 printk messages dropped **
> > ...
> > [  246.742374] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> > low, using default minimum of 512
> > [  246.742484] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> > low, using default minimum of 512
> > [  246.742590] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> > low, using default minimum of 512
> > 
> > Looks like a different issue.
> > 
> 
> Oh. I guess this is caused by the interface having a MTU smaller than
> SCTP_DEFAULT_MINSEGMENT (512), as the icmp frag needed handler
> (sctp_icmp_frag_needed) will trigger an instant retransmission.
> But as the MTU is smaller, SCTP won't update it, but will issue the
> retransmission anyway.
> 
> I will test this soon. Should be fairly easy to trigger it.

Reproduced it.

netns A veth0(1500) - veth1(1500) B veth2(508) - veth3(508) C

When A sends a sctp packet bigger than 508, it triggers the issue as B
will reply a icmp frag needed with a size that sctp won't accept but
will retransmit anyway.

  Marcelo

Re: INFO: task hung in bpf_exit_net

[Eric Biggers]

On Fri, Dec 22, 2017 at 05:04:37PM -0200, Marcelo Ricardo Leitner wrote:
> On Fri, Dec 22, 2017 at 04:28:07PM -0200, Marcelo Ricardo Leitner wrote:
> > On Fri, Dec 22, 2017 at 11:58:08AM +0100, Dmitry Vyukov wrote:
> > ...
> > > > Same with this one, perhaps related to / fixed by:
> > > >     http://patchwork.ozlabs.org/patch/850957/
> > > >
> > > 
> > > 
> > > 
> > > Looking at the log, this one seems to be an infinite loop in SCTP code
> > > with console output in it. Kernel is busy printing gazilion of:
> > > 
> > > [  176.491099] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> > > low, using default minimum of 512
> > > ** 110 printk messages dropped **
> > > [  176.503409] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> > > low, using default minimum of 512
> > > ** 103 printk messages dropped **
> > > ...
> > > [  246.742374] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> > > low, using default minimum of 512
> > > [  246.742484] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> > > low, using default minimum of 512
> > > [  246.742590] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> > > low, using default minimum of 512
> > > 
> > > Looks like a different issue.
> > > 
> > 
> > Oh. I guess this is caused by the interface having a MTU smaller than
> > SCTP_DEFAULT_MINSEGMENT (512), as the icmp frag needed handler
> > (sctp_icmp_frag_needed) will trigger an instant retransmission.
> > But as the MTU is smaller, SCTP won't update it, but will issue the
> > retransmission anyway.
> > 
> > I will test this soon. Should be fairly easy to trigger it.
> 
> Reproduced it.
> 
> netns A veth0(1500) - veth1(1500) B veth2(508) - veth3(508) C
> 
> When A sends a sctp packet bigger than 508, it triggers the issue as B
> will reply a icmp frag needed with a size that sctp won't accept but
> will retransmit anyway.
> 

syzbot hasn't encountered this hang again (although, it just happened once in
the first place).  I assume it was fixed by commit b6c5734db070, so telling
syzbot this:

#syz fix: sctp: fix the handling of ICMP Frag Needed for too small MTUs

- Eric