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Date:   Thu, 4 Jun 2020 13:41:07 +0200 (CEST)
From:   Jiri Kosina <jikos@kernel.org>
To:     Andrey Konovalov <andreyknvl@google.com>
cc:     syzbot <syzbot+6921abfb75d6fc79c0eb@syzkaller.appspotmail.com>,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>,
        "open list:HID CORE LAYER" <linux-input@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        amir73il@gmail.com, Felipe Balbi <balbi@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jan Kara <jack@suse.cz>, kuba@kernel.org,
        linux-fsdevel@vger.kernel.org, mathew.j.martineau@linux.intel.com,
        matthieu.baerts@tessares.net, mptcp@lists.01.org,
        netdev <netdev@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Peter Hutterer <peter.hutterer@who-t.net>
Subject: Re: INFO: task hung in corrupted (2)
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On Tue, 2 Jun 2020, Andrey Konovalov wrote:

> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit:    b0c3ba31 Merge tag 'fsnotify_for_v5.7-rc8' of git://git.ke..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=14089eee100000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=ce116858301bc2ea
> > dashboard link: https://syzkaller.appspot.com/bug?extid=6921abfb75d6fc79c0eb
> > compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14947d26100000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=172726d2100000
> >
> > The bug was bisected to:
> >
> > commit f2c2e717642c66f7fe7e5dd69b2e8ff5849f4d10
> > Author: Andrey Konovalov <andreyknvl@google.com>
> > Date:   Mon Feb 24 16:13:03 2020 +0000
> >
> >     usb: gadget: add raw-gadget interface
> >
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=119e4702100000
> > final crash:    https://syzkaller.appspot.com/x/report.txt?x=139e4702100000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=159e4702100000
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+6921abfb75d6fc79c0eb@syzkaller.appspotmail.com
> > Fixes: f2c2e717642c ("usb: gadget: add raw-gadget interface")
> >
> > INFO: task syz-executor610:7072 blocked for more than 143 seconds.
> >       Not tainted 5.7.0-rc7-syzkaller #0
> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > syz-executor610 D24336  7072   7071 0x80004002
> > Call Trace:
> >  context_switch kernel/sched/core.c:3367 [inline]
> >  __schedule+0x805/0xc90 kernel/sched/core.c:4083
> >
> > Showing all locks held in the system:
> > 1 lock held by khungtaskd/1134:
> >  #0: ffffffff892e85d0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30 net/mptcp/pm_netlink.c:860
> > 1 lock held by in:imklog/6715:
> >  #0: ffff8880a441e6b0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x25d/0x2f0 fs/file.c:826
> > 6 locks held by kworker/1:0/7064:
> > 1 lock held by syz-executor610/7072:
> >  #0: ffffffff892eab20 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:290 [inline]
> >  #0: ffffffff892eab20 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x1bd/0x5b0 kernel/rcu/tree_exp.h:856
> > 4 locks held by systemd-udevd/7099:
> >  #0: ffff8880a7fdcc70 (&p->lock){+.+.}-{3:3}, at: seq_read+0x60/0xce0 fs/seq_file.c:153
> >  #1: ffff888096486888 (&of->mutex){+.+.}-{3:3}, at: kernfs_seq_start+0x50/0x3b0 fs/kernfs/file.c:111
> >  #2: ffff88809fc0d660 (kn->count#78){.+.+}-{0:0}, at: kernfs_seq_start+0x6f/0x3b0 fs/kernfs/file.c:112
> >  #3: ffff8880a1df7218 (&dev->mutex){....}-{3:3}, at: device_lock_interruptible include/linux/device.h:773 [inline]
> >  #3: ffff8880a1df7218 (&dev->mutex){....}-{3:3}, at: serial_show+0x22/0xa0 drivers/usb/core/sysfs.c:142
> >
> > =============================================
> >
> > NMI backtrace for cpu 0
> > CPU: 0 PID: 1134 Comm: khungtaskd Not tainted 5.7.0-rc7-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > Call Trace:
> >  __dump_stack lib/dump_stack.c:77 [inline]
> >  dump_stack+0x1e9/0x30e lib/dump_stack.c:118
> >  nmi_cpu_backtrace+0x9f/0x180 lib/nmi_backtrace.c:101
> >  nmi_trigger_cpumask_backtrace+0x16a/0x280 lib/nmi_backtrace.c:62
> >  check_hung_uninterruptible_tasks kernel/hung_task.c:205 [inline]
> >  watchdog+0xd2a/0xd40 kernel/hung_task.c:289
> >  kthread+0x353/0x380 kernel/kthread.c:268
> >  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:351
> > Sending NMI from CPU 0 to CPUs 1:
> > NMI backtrace for cpu 1
> > CPU: 1 PID: 7064 Comm: kworker/1:0 Not tainted 5.7.0-rc7-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > Workqueue: usb_hub_wq hub_event
> > RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x0/0x90 kernel/kcov.c:275
> > Code: 4c f2 08 48 c1 e0 03 48 83 c8 18 49 89 14 02 4d 89 44 f2 18 49 ff c1 4d 89 0a c3 0f 1f 44 00 00 66 2e 0f 1f 84 00 00 00 00 00 <4c> 8b 04 24 65 48 8b 04 25 40 1e 02 00 65 8b 0d 78 96 8e 7e f7 c1
> > RSP: 0018:ffffc90001676cf0 EFLAGS: 00000246
> > RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88809fb9e240
> > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000ffffffff
> > RBP: ffff888092d24a04 R08: ffffffff86034f3b R09: ffffc900016790cc
> > R10: 0000000000000004 R11: 0000000000000000 R12: ffff888092d24a00
> > R13: 0000000000000000 R14: dffffc0000000000 R15: ffff888092d24a00
> > FS:  0000000000000000(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00000000004c6e68 CR3: 0000000092d41000 CR4: 00000000001406e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >  hid_apply_multiplier drivers/hid/hid-core.c:1106 [inline]
> 
> Looks like an issue in the HID subsystem, adding HID maintainers.

So this is hanging indefinitely in either of the loops in 
hid_apply_multiplier(). We'll have to decipher the reproducer to 
understand what made the loop (and which one) unbounded.

In parallel, CCing Peter, who wrote that code in the first place.

> 
> >  hid_setup_resolution_multiplier+0x2ab/0xbe0 drivers/hid/hid-core.c:1163
> >  hid_open_report+0xab2/0xdd0 drivers/hid/hid-core.c:1274
> >  hid_parse include/linux/hid.h:1017 [inline]
> >  ms_probe+0x12f/0x3f0 drivers/hid/hid-microsoft.c:388
> >  hid_device_probe+0x26c/0x410 drivers/hid/hid-core.c:2263
> >  really_probe+0x704/0xf60 drivers/base/dd.c:520
> >  driver_probe_device+0xe6/0x230 drivers/base/dd.c:697
> >  bus_for_each_drv+0x108/0x170 drivers/base/bus.c:431
> >  __device_attach+0x20c/0x3a0 drivers/base/dd.c:870
> >  bus_probe_device+0xb8/0x1f0 drivers/base/bus.c:491
> >  device_add+0x1828/0x1ba0 drivers/base/core.c:2557
> >  hid_add_device+0xa2a/0xef0 drivers/hid/hid-core.c:2419
> >  usbhid_probe+0x9bd/0xd10 drivers/hid/usbhid/hid-core.c:1407
> >  usb_probe_interface+0x614/0xac0 drivers/usb/core/driver.c:374
> >  really_probe+0x761/0xf60 drivers/base/dd.c:524
> >  driver_probe_device+0xe6/0x230 drivers/base/dd.c:697
> >  bus_for_each_drv+0x108/0x170 drivers/base/bus.c:431
> >  __device_attach+0x20c/0x3a0 drivers/base/dd.c:870
> >  bus_probe_device+0xb8/0x1f0 drivers/base/bus.c:491
> >  device_add+0x1828/0x1ba0 drivers/base/core.c:2557
> >  usb_set_configuration+0x19d2/0x1f20 drivers/usb/core/message.c:2032
> >  usb_generic_driver_probe+0x82/0x140 drivers/usb/core/generic.c:241
> >  usb_probe_device+0x12d/0x1d0 drivers/usb/core/driver.c:272
> >  really_probe+0x761/0xf60 drivers/base/dd.c:524
> >  driver_probe_device+0xe6/0x230 drivers/base/dd.c:697
> >  bus_for_each_drv+0x108/0x170 drivers/base/bus.c:431
> >  __device_attach+0x20c/0x3a0 drivers/base/dd.c:870
> >  bus_probe_device+0xb8/0x1f0 drivers/base/bus.c:491
> >  device_add+0x1828/0x1ba0 drivers/base/core.c:2557
> >  usb_new_device+0xcc3/0x1650 drivers/usb/core/hub.c:2554
> >  hub_port_connect drivers/usb/core/hub.c:5208 [inline]
> >  hub_port_connect_change drivers/usb/core/hub.c:5348 [inline]
> >  port_event drivers/usb/core/hub.c:5494 [inline]
> >  hub_event+0x2823/0x4cb0 drivers/usb/core/hub.c:5576
> >  process_one_work+0x76e/0xfd0 kernel/workqueue.c:2268
> >  worker_thread+0xa7f/0x1450 kernel/workqueue.c:2414
> >  kthread+0x353/0x380 kernel/kthread.c:268
> >  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:351
> >
> >
> > ---
> > This bug is generated by a bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for more information about syzbot.
> > syzbot engineers can be reached at syzkaller@googlegroups.com.
> >
> > syzbot will keep track of this bug report. See:
> > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> > syzbot can test patches for this bug, for details see:
> > https://goo.gl/tpsmEJ#testing-patches
> 

-- 
Jiri Kosina
SUSE Labs