Message-ID: <20171222111602.GB32765@localhost.localdomain>
Date:   Fri, 22 Dec 2017 09:16:02 -0200
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     David Ahern <dsahern@...il.com>,
        syzbot 
        <bot+21b498fc12cf2041655f8e1eeae0733807d794b3@...kaller.appspotmail.com>,
        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>,
        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>,
        Neil Horman <nhorman@...driver.com>, linux-sctp@...r.kernel.org
Subject: Re: INFO: task hung in bpf_exit_net

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@...il.com> wrote:
> > On 12/19/17 5:47 AM, Dmitry Vyukov wrote:
> >> On Tue, Dec 19, 2017 at 1:36 PM, syzbot
> >> <bot+21b498fc12cf2041655f8e1eeae0733807d794b3@...kaller.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@...glegroups.com.
> >>> Please credit me with: Reported-by: syzbot <syzkaller@...glegroups.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@...glegroups.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.
> 

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