[v5.15] INFO: task hung in drop_current_rng

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d214f240b0f6 Linux 5.15.100
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=12022f7ac80000
kernel config: https://syzkaller.appspot.com/x/.config?x=c5c5a36ceb954515
dashboard link: https://syzkaller.appspot.com/bug?extid=bd0cbd9be58dd01b6a24
compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4e12037285d4/disk-d214f240.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/929d982226d5/vmlinux-d214f240.xz
kernel image: https://storage.googleapis.com/syzbot-assets/59140c032c99/bzImage-d214f240.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bd0cbd...@syzkaller.appspotmail.com

INFO: task kworker/0:2:20553 blocked for more than 147 seconds.
Not tainted 5.15.100-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/0:2 state:D stack:23264 pid:20553 ppid: 2 flags:0x00004000
Workqueue: usb_hub_wq hub_event
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5023 [inline]
__schedule+0x1348/0x4610 kernel/sched/core.c:6369
schedule+0x11b/0x1f0 kernel/sched/core.c:6452
schedule_timeout+0xac/0x300 kernel/time/timer.c:1860
do_wait_for_common+0x2d9/0x480 kernel/sched/completion.c:85
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x48/0x60 kernel/sched/completion.c:138
cleanup_rng drivers/char/hw_random/core.c:82 [inline]
kref_put include/linux/kref.h:65 [inline]
drop_current_rng+0x8b/0xf0 drivers/char/hw_random/core.c:110
set_current_rng+0x3ad/0x530 drivers/char/hw_random/core.c:97
hwrng_register+0x34a/0x4c0 drivers/char/hw_random/core.c:500
chaoskey_probe+0x79d/0xb40 drivers/usb/misc/chaoskey.c:205
usb_probe_interface+0x5c0/0xaf0 drivers/usb/core/driver.c:396
really_probe+0x24e/0xb60 drivers/base/dd.c:595
__driver_probe_device+0x1c3/0x3f0 drivers/base/dd.c:750
driver_probe_device+0x50/0x420 drivers/base/dd.c:780
__device_attach_driver+0x2b9/0x500 drivers/base/dd.c:902
bus_for_each_drv+0x183/0x200 drivers/base/bus.c:427
__device_attach+0x359/0x570 drivers/base/dd.c:974
bus_probe_device+0xba/0x1e0 drivers/base/bus.c:487
device_add+0xb48/0xfd0 drivers/base/core.c:3394
usb_set_configuration+0x19dd/0x2020 drivers/usb/core/message.c:2170
usb_generic_driver_probe+0x84/0x140 drivers/usb/core/generic.c:238
usb_probe_device+0x130/0x260 drivers/usb/core/driver.c:293
really_probe+0x24e/0xb60 drivers/base/dd.c:595
__driver_probe_device+0x1c3/0x3f0 drivers/base/dd.c:750
driver_probe_device+0x50/0x420 drivers/base/dd.c:780
__device_attach_driver+0x2b9/0x500 drivers/base/dd.c:902
bus_for_each_drv+0x183/0x200 drivers/base/bus.c:427
__device_attach+0x359/0x570 drivers/base/dd.c:974
bus_probe_device+0xba/0x1e0 drivers/base/bus.c:487
device_add+0xb48/0xfd0 drivers/base/core.c:3394
usb_new_device+0xc17/0x18d0 drivers/usb/core/hub.c:2568
hub_port_connect drivers/usb/core/hub.c:5358 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5502 [inline]
port_event drivers/usb/core/hub.c:5648 [inline]
hub_event+0x2dd8/0x56d0 drivers/usb/core/hub.c:5730
process_one_work+0x90d/0x1270 kernel/workqueue.c:2306
worker_thread+0xaca/0x1280 kernel/workqueue.c:2453
kthread+0x3f6/0x4f0 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 <unknown>:298
</TASK>
INFO: task kworker/0:16:30766 blocked for more than 151 seconds.
Not tainted 5.15.100-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/0:16 state:D stack:23512 pid:30766 ppid: 2 flags:0x00004000
Workqueue: usb_hub_wq hub_event
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5023 [inline]
__schedule+0x1348/0x4610 kernel/sched/core.c:6369
schedule+0x11b/0x1f0 kernel/sched/core.c:6452
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6511
__mutex_lock_common+0xe34/0x25a0 kernel/locking/mutex.c:669
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
hwrng_register+0xa9/0x4c0 drivers/char/hw_random/core.c:473
chaoskey_probe+0x79d/0xb40 drivers/usb/misc/chaoskey.c:205
usb_probe_interface+0x5c0/0xaf0 drivers/usb/core/driver.c:396
really_probe+0x24e/0xb60 drivers/base/dd.c:595
__driver_probe_device+0x1c3/0x3f0 drivers/base/dd.c:750
driver_probe_device+0x50/0x420 drivers/base/dd.c:780
__device_attach_driver+0x2b9/0x500 drivers/base/dd.c:902
bus_for_each_drv+0x183/0x200 drivers/base/bus.c:427
__device_attach+0x359/0x570 drivers/base/dd.c:974
bus_probe_device+0xba/0x1e0 drivers/base/bus.c:487
device_add+0xb48/0xfd0 drivers/base/core.c:3394
usb_set_configuration+0x19dd/0x2020 drivers/usb/core/message.c:2170
usb_generic_driver_probe+0x84/0x140 drivers/usb/core/generic.c:238
usb_probe_device+0x130/0x260 drivers/usb/core/driver.c:293
really_probe+0x24e/0xb60 drivers/base/dd.c:595
__driver_probe_device+0x1c3/0x3f0 drivers/base/dd.c:750
driver_probe_device+0x50/0x420 drivers/base/dd.c:780
__device_attach_driver+0x2b9/0x500 drivers/base/dd.c:902
bus_for_each_drv+0x183/0x200 drivers/base/bus.c:427
__device_attach+0x359/0x570 drivers/base/dd.c:974
bus_probe_device+0xba/0x1e0 drivers/base/bus.c:487
device_add+0xb48/0xfd0 drivers/base/core.c:3394
usb_new_device+0xc17/0x18d0 drivers/usb/core/hub.c:2568
hub_port_connect drivers/usb/core/hub.c:5358 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5502 [inline]
port_event drivers/usb/core/hub.c:5648 [inline]
hub_event+0x2dd8/0x56d0 drivers/usb/core/hub.c:5730
process_one_work+0x90d/0x1270 kernel/workqueue.c:2306
worker_thread+0xaca/0x1280 kernel/workqueue.c:2453
kthread+0x3f6/0x4f0 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 <unknown>:298
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/27:
#0: ffffffff8c91c2a0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
1 lock held by hwrng/901:
#0: ffffffff8cff33e8 (rng_mutex){+.+.}-{3:3}, at: get_current_rng drivers/char/hw_random/core.c:127 [inline]
#0: ffffffff8cff33e8 (rng_mutex){+.+.}-{3:3}, at: hwrng_fillfn+0x36/0x280 drivers/char/hw_random/core.c:433
2 locks held by getty/3274:
#0: ffff8880231da098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
#1: ffffc90002bb62e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6af/0x1da0 drivers/tty/n_tty.c:2147
2 locks held by kworker/u4:7/3741:
4 locks held by kworker/u4:3/13378:
6 locks held by kworker/0:2/20553:
#0: ffff888012da4138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x794/0x1270 kernel/workqueue.c:2279
#1: ffffc90005d07d20 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x7da/0x1270 kernel/workqueue.c:2281
#2: ffff888147604220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:760 [inline]
#2: ffff888147604220 (&dev->mutex){....}-{3:3}, at: hub_event+0x207/0x56d0 drivers/usb/core/hub.c:5676
#3: ffff888079aea220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:760 [inline]
#3: ffff888079aea220 (&dev->mutex){....}-{3:3}, at: __device_attach+0x8a/0x570 drivers/base/dd.c:949
#4: ffff888079aed1a8 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:760 [inline]
#4: ffff888079aed1a8 (&dev->mutex){....}-{3:3}, at: __device_attach+0x8a/0x570 drivers/base/dd.c:949
#5: ffffffff8cff33e8 (rng_mutex){+.+.}-{3:3}, at: hwrng_register+0xa9/0x4c0 drivers/char/hw_random/core.c:473
3 locks held by kworker/1:20/23726:
#0: ffff888011c64d38 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x794/0x1270 kernel/workqueue.c:2279
#1: ffffc9000b5e7d20 ((work_completion)(&pwq->unbound_release_work)){+.+.}-{0:0}, at: process_one_work+0x7da/0x1270 kernel/workqueue.c:2281
#2: ffffffff8c9207e8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:290 [inline]
#2: ffffffff8c9207e8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x280/0x740 kernel/rcu/tree_exp.h:840
6 locks held by kworker/0:16/30766:
#0: ffff888012da4138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x794/0x1270 kernel/workqueue.c:2279
#1: ffffc9000443fd20 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x7da/0x1270 kernel/workqueue.c:2281
#2: ffff888147ede220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:760 [inline]
#2: ffff888147ede220 (&dev->mutex){....}-{3:3}, at: hub_event+0x207/0x56d0 drivers/usb/core/hub.c:5676
#3: ffff888079ae8220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:760 [inline]
#3: ffff888079ae8220 (&dev->mutex){....}-{3:3}, at: __device_attach+0x8a/0x570 drivers/base/dd.c:949
#4: ffff88801e9a31a8 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:760 [inline]
#4: ffff88801e9a31a8 (&dev->mutex){....}-{3:3}, at: __device_attach+0x8a/0x570 drivers/base/dd.c:949
#5: ffffffff8cff33e8 (rng_mutex){+.+.}-{3:3}, at: hwrng_register+0xa9/0x4c0 drivers/char/hw_random/core.c:473
3 locks held by kworker/0:18/30772:
#0: ffff888011c64d38 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x794/0x1270 kernel/workqueue.c:2279
#1: ffffc90004247d20 (key_gc_work){+.+.}-{0:0}, at: process_one_work+0x7da/0x1270 kernel/workqueue.c:2281
#2: ffffffff8c9207e8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:322 [inline]
#2: ffffffff8c9207e8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x350/0x740 kernel/rcu/tree_exp.h:840
3 locks held by kworker/1:2/30840:
#0: ffff888011c64d38 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x794/0x1270 kernel/workqueue.c:2279
#1: ffffc90004b7fd20 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work+0x7da/0x1270 kernel/workqueue.c:2281
#2: ffffffff8d9d8f68 (rtnl_mutex){+.+.}-{3:3}, at: linkwatch_event+0xa/0x50 net/core/link_watch.c:251
2 locks held by kworker/1:4/30842:
#0: ffff888011c66538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x794/0x1270 kernel/workqueue.c:2279
#1: ffffc90004bafd20 ((work_completion)(&rew.rew_work)){+.+.}-{0:0}, at: process_one_work+0x7da/0x1270 kernel/workqueue.c:2281
4 locks held by udevd/972:
#0: ffff888073d478b8 (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0xae/0xd10 fs/seq_file.c:182
#1: ffff88801bed1c88 (&of->mutex){+.+.}-{3:3}, at: kernfs_seq_start+0x50/0x3b0 fs/kernfs/file.c:112
#2: ffff88807da4c578 (kn->active#87){++++}-{0:0}, at: kernfs_seq_start+0x6f/0x3b0 fs/kernfs/file.c:113
#3: ffff888079ae8220 (&dev->mutex){....}-{3:3}, at: device_lock_interruptible include/linux/device.h:765 [inline]
#3: ffff888079ae8220 (&dev->mutex){....}-{3:3}, at: manufacturer_show+0x22/0x90 drivers/usb/core/sysfs.c:141
3 locks held by syz-executor.3/4332:
3 locks held by syz-executor.3/4410:
2 locks held by syz-executor.5/4415:
#0: ffff88805c7ad010 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
#0: ffff88805c7ad010 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: __sock_release net/socket.c:648 [inline]
#0: ffff88805c7ad010 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: sock_close+0x98/0x230 net/socket.c:1317
#1: ffff88807e21f120 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1649 [inline]
#1: ffff88807e21f120 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pptp_release+0x4e/0x2f0 drivers/net/ppp/pptp.c:499
1 lock held by syz-executor.4/4418:
#0: ffffffff8d9d8f68 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:72 [inline]
#0: ffffffff8d9d8f68 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x94c/0xee0 net/core/rtnetlink.c:5584
2 locks held by syz-executor.3/4423:
#0: ffffffff8d9cd210 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x37b/0x5d0 net/core/net_namespace.c:469
#1: ffffffff8d9d8f68 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:799 [inline]
#1: ffffffff8d9d8f68 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x176/0x3b0 net/smc/smc_pnet.c:868
1 lock held by dhcpcd/4430:
#0: ffff888079a5c120 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1649 [inline]
#0: ffff888079a5c120 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2a/0xc90 net/packet/af_packet.c:3159
2 locks held by syz-executor.0/4432:

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted 5.15.100-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
nmi_cpu_backtrace+0x46a/0x4a0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x181/0x2a0 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:210 [inline]
watchdog+0xf54/0xfa0 kernel/hung_task.c:295
kthread+0x3f6/0x4f0 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 <unknown>:298
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 3608 Comm: syz-executor.0 Not tainted 5.15.100-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
RIP: 0010:validate_chain+0x11/0x58b0 kernel/locking/lockdep.c:3743
Code: bb e3 8d e8 d1 86 66 00 eb 84 e8 fa 5b bf 08 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 57 41 56 41 55 41 54 53 48 83 e4 e0 <48> 81 ec 80 02 00 00 49 89 ce 89 54 24 58 48 89 7c 24 78 65 48 8b
RSP: 0018:ffffc90002d4f6e0 EFLAGS: 00000082
RAX: 1ffffffff1f15f8c RBX: ffffffff8f8afc60 RCX: f3e939ec8e99e7f8
RDX: 0000000000000001 RSI: ffff88802436a720 RDI: ffff888024369d00
RBP: ffffc90002d4f710 R08: dffffc0000000000 R09: fffffbfff1f76417
R10: 0000000000000000 R11: dffffc0000000001 R12: 0000000000000000
R13: ffff88802436a718 R14: ffff888024369d00 R15: ffff88802436a740
FS: 0000555556e12400(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555556b7e708 CR3: 00000000585e4000 CR4: 00000000003506e0
Call Trace:
<TASK>
__lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5011
lock_acquire+0x1ff/0x570 kernel/locking/lockdep.c:5622
do_write_seqcount_begin_nested include/linux/seqlock.h:520 [inline]
do_write_seqcount_begin include/linux/seqlock.h:545 [inline]
vtime_task_switch_generic+0xb0/0x590 kernel/sched/cputime.c:768
vtime_task_switch include/linux/vtime.h:95 [inline]
finish_task_switch+0x3ea/0x630 kernel/sched/core.c:4891
context_switch kernel/sched/core.c:5026 [inline]
__schedule+0x1350/0x4610 kernel/sched/core.c:6369
schedule+0x11b/0x1f0 kernel/sched/core.c:6452
freezable_schedule include/linux/freezer.h:172 [inline]
do_nanosleep+0x1bc/0x7b0 kernel/time/hrtimer.c:2044
hrtimer_nanosleep+0x24d/0x490 kernel/time/hrtimer.c:2097
__do_sys_clock_nanosleep kernel/time/posix-timers.c:1277 [inline]
__se_sys_clock_nanosleep+0x323/0x3b0 kernel/time/posix-timers.c:1254
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7fc203f34e21
Code: 24 0c 89 3c 24 48 89 4c 24 18 e8 aa e7 ff ff 4c 8b 54 24 18 48 8b 54 24 10 41 89 c0 8b 74 24 0c 8b 3c 24 b8 e6 00 00 00 0f 05 <44> 89 c7 48 89 04 24 e8 e3 e7 ff ff 48 8b 04 24 eb 97 66 2e 0f 1f
RSP: 002b:00007fff49c034a0 EFLAGS: 00000293 ORIG_RAX: 00000000000000e6
RAX: ffffffffffffffda RBX: 000000000000144c RCX: 00007fc203f34e21
RDX: 00007fff49c034e0 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fff49c0356c R08: 0000000000000000 R09: 0000000000000010
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000032
R13: 000000000026d61e R14: 0000000000000001 R15: 00007fff49c035d0
</TASK>


---
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.

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 8020ae3c051d Linux 5.15.103
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1685219ac80000
kernel config: https://syzkaller.appspot.com/x/.config?x=d4215fb4040f8f8d

dashboard link: https://syzkaller.appspot.com/bug?extid=bd0cbd9be58dd01b6a24
compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10758a16c80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=111097bec80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/857e17de0f0a/disk-8020ae3c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9efc49fcd441/vmlinux-8020ae3c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f14c38b6bfa7/bzImage-8020ae3c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bd0cbd...@syzkaller.appspotmail.com

INFO: task kworker/1:3:1908 blocked for more than 143 seconds.
Not tainted 5.15.103-syzkaller #0

"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:kworker/1:3 state:D stack:22272 pid: 1908 ppid: 2 flags:0x00004000

ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/27:

#0: ffffffff8c91c320 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
1 lock held by hwrng/900:
#0: ffffffff8cff3468 (rng_mutex){+.+.}-{3:3}, at: get_current_rng drivers/char/hw_random/core.c:127 [inline]
#0: ffffffff8cff3468 (rng_mutex){+.+.}-{3:3}, at: hwrng_fillfn+0x36/0x280 drivers/char/hw_random/core.c:433
6 locks held by kworker/1:3/1908:
#0: ffff888016b75938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x794/0x1270 kernel/workqueue.c:2279
#1: ffffc90005b77d20 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x7da/0x1270 kernel/workqueue.c:2281
#2: ffff8881475c8220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:760 [inline]
#2: ffff8881475c8220 (&dev->mutex){....}-{3:3}, at: hub_event+0x207/0x56d0 drivers/usb/core/hub.c:5676
#3: ffff88801a406220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:760 [inline]
#3: ffff88801a406220 (&dev->mutex){....}-{3:3}, at: __device_attach+0x8a/0x570 drivers/base/dd.c:949
#4: ffff88801a4071a8 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:760 [inline]
#4: ffff88801a4071a8 (&dev->mutex){....}-{3:3}, at: __device_attach+0x8a/0x570 drivers/base/dd.c:949
#5: ffffffff8cff3468 (rng_mutex){+.+.}-{3:3}, at: hwrng_register+0xa9/0x4c0 drivers/char/hw_random/core.c:473

2 locks held by getty/3274:

#0: ffff88814b21f098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
#1: ffffc90002bb32e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6af/0x1da0 drivers/tty/n_tty.c:2147

=============================================

NMI backtrace for cpu 0

CPU: 0 PID: 27 Comm: khungtaskd Not tainted 5.15.103-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
nmi_cpu_backtrace+0x46a/0x4a0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x181/0x2a0 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:210 [inline]
watchdog+0xf54/0xfa0 kernel/hung_task.c:295
kthread+0x3f6/0x4f0 kernel/kthread.c:319

ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

</TASK>
Sending NMI from CPU 0 to CPUs 1:

NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_safe_halt drivers/acpi/processor_idle.c:109 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_idle_do_entry+0x10f/0x340 drivers/acpi/processor_idle.c:570

[syzbot]

syzbot suspects this issue was fixed by commit:

commit f5634d21541efab5712c2e948b32cdc3c9f00752
Author: Laurent Vivier <lvi...@redhat.com>
Date: Thu Oct 28 10:11:09 2021 +0000

hwrng: virtio - don't wait on cleanup

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=12fcf821680000
start commit: 8a7f2a5c5aa1 Linux 5.15.110
git tree: linux-5.15.y
kernel config: https://syzkaller.appspot.com/x/.config?x=ba8d5c9d6c5289f
dashboard link: https://syzkaller.appspot.com/bug?extid=bd0cbd9be58dd01b6a24
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1745bbf4280000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=130487d4280000

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

#syz fix: hwrng: virtio - don't wait on cleanup

For information about bisection process see: https://goo.gl/tpsmEJ#bisection