INFO: task hung in usb_get_descriptor

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d3d45f82 Merge tag 'pinctrl-v5.9-2' of git://git.kernel.or..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1318aab7900000
kernel config: https://syzkaller.appspot.com/x/.config?x=89ab6a0c48f30b49
dashboard link: https://syzkaller.appspot.com/bug?extid=31ae6d17d115e980fd14
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17c69eeb900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17bebadb900000

The issue was bisected to:

commit c0303efeab7391ec51c337e0ac5740860ad01fe7
Author: Jesper Dangaard Brouer <bro...@redhat.com>
Date: Mon Jan 9 15:04:09 2017 +0000

net: reduce cycles spend on ICMP replies that gets rate limited

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=146872af900000
final oops: https://syzkaller.appspot.com/x/report.txt?x=166872af900000
console output: https://syzkaller.appspot.com/x/log.txt?x=126872af900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+31ae6d...@syzkaller.appspotmail.com
Fixes: c0303efeab73 ("net: reduce cycles spend on ICMP replies that gets rate limited")

INFO: task kworker/0:0:5 blocked for more than 143 seconds.
Not tainted 5.9.0-rc7-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/0:0 state:D stack:27376 pid: 5 ppid: 2 flags:0x00004000
Workqueue: usb_hub_wq hub_event
Call Trace:
context_switch kernel/sched/core.c:3778 [inline]
__schedule+0xec9/0x2280 kernel/sched/core.c:4527
schedule+0xd0/0x2a0 kernel/sched/core.c:4602
usb_kill_urb.part.0+0x197/0x220 drivers/usb/core/urb.c:696
usb_kill_urb+0x7c/0x90 drivers/usb/core/urb.c:691
usb_start_wait_urb+0x24a/0x2b0 drivers/usb/core/message.c:64
usb_internal_control_msg drivers/usb/core/message.c:102 [inline]
usb_control_msg+0x31c/0x4a0 drivers/usb/core/message.c:153
usb_get_descriptor+0xc5/0x1b0 drivers/usb/core/message.c:655
usb_get_device_descriptor+0x81/0xf0 drivers/usb/core/message.c:927
hub_port_init+0x78f/0x2d80 drivers/usb/core/hub.c:4784
hub_port_connect drivers/usb/core/hub.c:5140 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5348 [inline]
port_event drivers/usb/core/hub.c:5494 [inline]
hub_event+0x1e64/0x3e60 drivers/usb/core/hub.c:5576
process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
process_scheduled_works kernel/workqueue.c:2331 [inline]
worker_thread+0x82b/0x1120 kernel/workqueue.c:2417
kthread+0x3b5/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
INFO: task kworker/0:2:2474 blocked for more than 144 seconds.
Not tainted 5.9.0-rc7-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/0:2 state:D stack:27416 pid: 2474 ppid: 2 flags:0x00004000
Workqueue: usb_hub_wq hub_event
Call Trace:
context_switch kernel/sched/core.c:3778 [inline]
__schedule+0xec9/0x2280 kernel/sched/core.c:4527
schedule+0xd0/0x2a0 kernel/sched/core.c:4602
usb_kill_urb.part.0+0x197/0x220 drivers/usb/core/urb.c:696
usb_kill_urb+0x7c/0x90 drivers/usb/core/urb.c:691
usb_start_wait_urb+0x24a/0x2b0 drivers/usb/core/message.c:64
usb_internal_control_msg drivers/usb/core/message.c:102 [inline]
usb_control_msg+0x31c/0x4a0 drivers/usb/core/message.c:153
usb_get_descriptor+0xc5/0x1b0 drivers/usb/core/message.c:655
usb_get_device_descriptor+0x81/0xf0 drivers/usb/core/message.c:927
hub_port_init+0x78f/0x2d80 drivers/usb/core/hub.c:4784
hub_port_connect drivers/usb/core/hub.c:5140 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5348 [inline]
port_event drivers/usb/core/hub.c:5494 [inline]
hub_event+0x1e64/0x3e60 drivers/usb/core/hub.c:5576
process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
kthread+0x3b5/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
INFO: task kworker/1:2:2597 blocked for more than 145 seconds.
Not tainted 5.9.0-rc7-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/1:2 state:D stack:26824 pid: 2597 ppid: 2 flags:0x00004000
Workqueue: usb_hub_wq hub_event
Call Trace:
context_switch kernel/sched/core.c:3778 [inline]
__schedule+0xec9/0x2280 kernel/sched/core.c:4527
schedule+0xd0/0x2a0 kernel/sched/core.c:4602
usb_kill_urb.part.0+0x197/0x220 drivers/usb/core/urb.c:696
usb_kill_urb+0x7c/0x90 drivers/usb/core/urb.c:691
usb_start_wait_urb+0x24a/0x2b0 drivers/usb/core/message.c:64
usb_internal_control_msg drivers/usb/core/message.c:102 [inline]
usb_control_msg+0x31c/0x4a0 drivers/usb/core/message.c:153
hub_port_init+0x11ae/0x2d80 drivers/usb/core/hub.c:4689
hub_port_connect drivers/usb/core/hub.c:5140 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5348 [inline]
port_event drivers/usb/core/hub.c:5494 [inline]
hub_event+0x1e64/0x3e60 drivers/usb/core/hub.c:5576
process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
process_scheduled_works kernel/workqueue.c:2331 [inline]
worker_thread+0x82b/0x1120 kernel/workqueue.c:2417
kthread+0x3b5/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
INFO: task kworker/1:1:6869 blocked for more than 147 seconds.
Not tainted 5.9.0-rc7-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/1:1 state:D stack:27848 pid: 6869 ppid: 2 flags:0x00004000
Workqueue: usb_hub_wq hub_event
Call Trace:
context_switch kernel/sched/core.c:3778 [inline]
__schedule+0xec9/0x2280 kernel/sched/core.c:4527
schedule+0xd0/0x2a0 kernel/sched/core.c:4602
usb_kill_urb.part.0+0x197/0x220 drivers/usb/core/urb.c:696
usb_kill_urb+0x7c/0x90 drivers/usb/core/urb.c:691
usb_start_wait_urb+0x24a/0x2b0 drivers/usb/core/message.c:64
usb_internal_control_msg drivers/usb/core/message.c:102 [inline]
usb_control_msg+0x31c/0x4a0 drivers/usb/core/message.c:153
hub_port_init+0x11ae/0x2d80 drivers/usb/core/hub.c:4689
hub_port_connect drivers/usb/core/hub.c:5140 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5348 [inline]
port_event drivers/usb/core/hub.c:5494 [inline]
hub_event+0x1e64/0x3e60 drivers/usb/core/hub.c:5576
process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
kthread+0x3b5/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
INFO: task kworker/1:3:6901 blocked for more than 149 seconds.
Not tainted 5.9.0-rc7-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/1:3 state:D stack:27264 pid: 6901 ppid: 2 flags:0x00004000
Workqueue: usb_hub_wq hub_event
Call Trace:
context_switch kernel/sched/core.c:3778 [inline]
__schedule+0xec9/0x2280 kernel/sched/core.c:4527
schedule+0xd0/0x2a0 kernel/sched/core.c:4602
usb_kill_urb.part.0+0x197/0x220 drivers/usb/core/urb.c:696
usb_kill_urb+0x7c/0x90 drivers/usb/core/urb.c:691
usb_start_wait_urb+0x24a/0x2b0 drivers/usb/core/message.c:64
usb_internal_control_msg drivers/usb/core/message.c:102 [inline]
usb_control_msg+0x31c/0x4a0 drivers/usb/core/message.c:153
hub_port_init+0x11ae/0x2d80 drivers/usb/core/hub.c:4689
hub_port_connect drivers/usb/core/hub.c:5140 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5348 [inline]
port_event drivers/usb/core/hub.c:5494 [inline]
hub_event+0x1e64/0x3e60 drivers/usb/core/hub.c:5576
process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
process_scheduled_works kernel/workqueue.c:2331 [inline]
worker_thread+0x82b/0x1120 kernel/workqueue.c:2417
kthread+0x3b5/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
INFO: task kworker/0:1:6919 blocked for more than 151 seconds.
Not tainted 5.9.0-rc7-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/0:1 state:D stack:27800 pid: 6919 ppid: 2 flags:0x00004000
Workqueue: usb_hub_wq hub_event
Call Trace:
context_switch kernel/sched/core.c:3778 [inline]
__schedule+0xec9/0x2280 kernel/sched/core.c:4527
schedule+0xd0/0x2a0 kernel/sched/core.c:4602
usb_kill_urb.part.0+0x197/0x220 drivers/usb/core/urb.c:696
usb_kill_urb+0x7c/0x90 drivers/usb/core/urb.c:691
usb_start_wait_urb+0x24a/0x2b0 drivers/usb/core/message.c:64
usb_internal_control_msg drivers/usb/core/message.c:102 [inline]
usb_control_msg+0x31c/0x4a0 drivers/usb/core/message.c:153
hub_port_init+0x11ae/0x2d80 drivers/usb/core/hub.c:4689
hub_port_connect drivers/usb/core/hub.c:5140 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5348 [inline]
port_event drivers/usb/core/hub.c:5494 [inline]
hub_event+0x1e64/0x3e60 drivers/usb/core/hub.c:5576
process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
process_scheduled_works kernel/workqueue.c:2331 [inline]
worker_thread+0x82b/0x1120 kernel/workqueue.c:2417
kthread+0x3b5/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Showing all locks held in the system:
5 locks held by kworker/0:0/5:
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline]
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline]
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x82b/0x1670 kernel/workqueue.c:2240
#1: ffffc90000cbfda8 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x85f/0x1670 kernel/workqueue.c:2244
#2: ffff888217a2e218 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:785 [inline]
#2: ffff888217a2e218 (&dev->mutex){....}-{3:3}, at: hub_event+0x1b6/0x3e60 drivers/usb/core/hub.c:5522
#3: ffff888217a35588 (&port_dev->status_lock){+.+.}-{3:3}, at: usb_lock_port drivers/usb/core/hub.c:3012 [inline]
#3: ffff888217a35588 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_port_connect drivers/usb/core/hub.c:5139 [inline]
#3: ffff888217a35588 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_port_connect_change drivers/usb/core/hub.c:5348 [inline]
#3: ffff888217a35588 (&port_dev->status_lock){+.+.}-{3:3}, at: port_event drivers/usb/core/hub.c:5494 [inline]
#3: ffff888217a35588 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_event+0x1e4f/0x3e60 drivers/usb/core/hub.c:5576
#4: ffff888217a28468 (hcd->address0_mutex){+.+.}-{3:3}, at: hub_port_init+0x1b6/0x2d80 drivers/usb/core/hub.c:4563
2 locks held by kworker/u4:0/7:
#0: ffff8880a7cad938 ((wq_completion)usbip_event){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ffff8880a7cad938 ((wq_completion)usbip_event){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
#0: ffff8880a7cad938 ((wq_completion)usbip_event){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline]
#0: ffff8880a7cad938 ((wq_completion)usbip_event){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline]
#0: ffff8880a7cad938 ((wq_completion)usbip_event){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
#0: ffff8880a7cad938 ((wq_completion)usbip_event){+.+.}-{0:0}, at: process_one_work+0x82b/0x1670 kernel/workqueue.c:2240
#1: ffffc90000cdfda8 (usbip_work){+.+.}-{0:0}, at: process_one_work+0x85f/0x1670 kernel/workqueue.c:2244
1 lock held by khungtaskd/1172:
#0: ffffffff8a067f40 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:5852
5 locks held by kworker/0:2/2474:
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline]
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline]
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x82b/0x1670 kernel/workqueue.c:2240
#1: ffffc9000859fda8 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x85f/0x1670 kernel/workqueue.c:2244
#2: ffff888217d02218 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:785 [inline]
#2: ffff888217d02218 (&dev->mutex){....}-{3:3}, at: hub_event+0x1b6/0x3e60 drivers/usb/core/hub.c:5522
#3: ffff8880a64c0588 (&port_dev->status_lock){+.+.}-{3:3}, at: usb_lock_port drivers/usb/core/hub.c:3012 [inline]
#3: ffff8880a64c0588 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_port_connect drivers/usb/core/hub.c:5139 [inline]
#3: ffff8880a64c0588 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_port_connect_change drivers/usb/core/hub.c:5348 [inline]
#3: ffff8880a64c0588 (&port_dev->status_lock){+.+.}-{3:3}, at: port_event drivers/usb/core/hub.c:5494 [inline]
#3: ffff8880a64c0588 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_event+0x1e4f/0x3e60 drivers/usb/core/hub.c:5576
#4: ffff8880a6c36968 (hcd->address0_mutex){+.+.}-{3:3}, at: hub_port_init+0x1b6/0x2d80 drivers/usb/core/hub.c:4563
5 locks held by kworker/1:2/2597:
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline]
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline]
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
#0: ffff88821a8df938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x82b/0x1670 kernel/workqueue.c:2240
#1: ffffc9000890fda8 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x85f/0x1670 kernel/workqueue.c:2244
#2: ffff8880a672c218 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:785 [inline]
#2: ffff8880a672c218 (&dev->mutex){....}-{3:3}, at: hub_event+0x1b6/0x3e60 drivers/usb/core/hub.c:5522


---
This report 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 syzk...@googlegroups.com.

syzbot will keep track of this issue. 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 issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Hillf Danton]

Tue, 06 Oct 2020 01:19:17

Dunno if a mb makes sense.

--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1656,6 +1656,7 @@ static void __usb_hcd_giveback_urb(struc
usb_anchor_resume_wakeups(anchor);

atomic_dec(&urb->use_count);
+ smp_mb__after_atomic();
if (unlikely(atomic_read(&urb->reject)))
wake_up(&usb_kill_urb_queue);

[syzbot]

syzbot suspects this issue was fixed by commit:

commit 363eaa3a450abb4e63bd6e3ad79d1f7a0f717814
Author: Shuah Khan <sk...@linuxfoundation.org>
Date: Tue Mar 30 01:36:51 2021 +0000

usbip: synchronize event handler with sysfs code paths

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1616e872700000
start commit: 4fa56ad0d12e Merge tag 'for-linus' of git://git.kernel.org..
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=144ecdb0be3abc07
dashboard link: https://syzkaller.appspot.com/bug?extid=31ae6d17d115e980fd14
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12548d11d00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13ec77e9d00000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: usbip: synchronize event handler with sysfs code paths

[Hillf Danton]

On Tue, 06 Oct 2020 01:19:17 -0700

See if the idea in Alan's fix [1] for the ordering on giving back urb works
in this case.

Hillf

[1] https://lore.kernel.org/lkml/YembypBP...@rowland.harvard.edu/

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/ d3d45f82

--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1652,6 +1652,7 @@ static void __usb_hcd_giveback_urb(struc

usb_anchor_resume_wakeups(anchor);
atomic_dec(&urb->use_count);
+ smp_mb__after_atomic();
if (unlikely(atomic_read(&urb->reject)))
wake_up(&usb_kill_urb_queue);

usb_put_urb(urb);
--

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: null-ptr-deref Write in vhci_shutdown_connection

==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_write include/linux/instrumented.h:71 [inline]
BUG: KASAN: null-ptr-deref in atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:142 [inline]
BUG: KASAN: null-ptr-deref in refcount_add include/linux/refcount.h:201 [inline]
BUG: KASAN: null-ptr-deref in refcount_inc include/linux/refcount.h:241 [inline]
BUG: KASAN: null-ptr-deref in get_task_struct include/linux/sched/task.h:104 [inline]
BUG: KASAN: null-ptr-deref in kthread_stop+0x90/0x810 kernel/kthread.c:591
Write of size 4 at addr 000000000000001c by task kworker/u4:4/186

CPU: 0 PID: 186 Comm: kworker/u4:4 Not tainted 5.9.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: usbip_event event_handler
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x107/0x16e lib/dump_stack.c:118
__kasan_report mm/kasan/report.c:517 [inline]
kasan_report.cold+0x5/0x37 mm/kasan/report.c:530
check_memory_region_inline mm/kasan/generic.c:186 [inline]
check_memory_region+0x13d/0x180 mm/kasan/generic.c:192
instrument_atomic_write include/linux/instrumented.h:71 [inline]
atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:142 [inline]
refcount_add include/linux/refcount.h:201 [inline]
refcount_inc include/linux/refcount.h:241 [inline]
get_task_struct include/linux/sched/task.h:104 [inline]
kthread_stop+0x90/0x810 kernel/kthread.c:591
vhci_shutdown_connection+0x17f/0x360 drivers/usb/usbip/vhci_hcd.c:1015
event_handler+0x1f0/0x4f0 drivers/usb/usbip/usbip_event.c:78
process_one_work+0x86c/0x16a0 kernel/workqueue.c:2269
worker_thread+0x64c/0x1120 kernel/workqueue.c:2415

kthread+0x3b5/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

==================================================================
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 186 Comm: kworker/u4:4 Tainted: G B 5.9.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: usbip_event event_handler
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x107/0x16e lib/dump_stack.c:118
panic+0x393/0x7d3 kernel/panic.c:231
end_report+0x4d/0x53 mm/kasan/report.c:104
__kasan_report mm/kasan/report.c:520 [inline]
kasan_report.cold+0xd/0x37 mm/kasan/report.c:530
check_memory_region_inline mm/kasan/generic.c:186 [inline]
check_memory_region+0x13d/0x180 mm/kasan/generic.c:192
instrument_atomic_write include/linux/instrumented.h:71 [inline]
atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:142 [inline]
refcount_add include/linux/refcount.h:201 [inline]
refcount_inc include/linux/refcount.h:241 [inline]
get_task_struct include/linux/sched/task.h:104 [inline]
kthread_stop+0x90/0x810 kernel/kthread.c:591
vhci_shutdown_connection+0x17f/0x360 drivers/usb/usbip/vhci_hcd.c:1015
event_handler+0x1f0/0x4f0 drivers/usb/usbip/usbip_event.c:78
process_one_work+0x86c/0x16a0 kernel/workqueue.c:2269
worker_thread+0x64c/0x1120 kernel/workqueue.c:2415

kthread+0x3b5/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Kernel Offset: disabled
Rebooting in 86400 seconds..


Tested on:

commit: d3d45f82 Merge tag 'pinctrl-v5.9-2' of git://git.kerne..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/
console output: https://syzkaller.appspot.com/x/log.txt?x=125b4faa700000
kernel config: https://syzkaller.appspot.com/x/.config?x=c4f7c05cb42b5045
dashboard link: https://syzkaller.appspot.com/bug?extid=31ae6d17d115e980fd14
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
patch: https://syzkaller.appspot.com/x/patch.diff?x=1359552c700000

[Hillf Danton]

On Sat, 12 Feb 2022 23:40:13 -0800

The task hung symptom disappears then see if the null-ptr-deref emerging in
this report is addressed in the mainline tree.

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+31ae6d...@syzkaller.appspotmail.com

Tested on:

commit: b81b1829 Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=d94e196c4f68081d

dashboard link: https://syzkaller.appspot.com/bug?extid=31ae6d17d115e980fd14
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

Note: testing is done by a robot and is best-effort only.

[Dmitry Vyukov]

Based on subsystem and commit subject looks legit: