syzbot


INFO: task hung in uhid_char_release

Status: upstream: reported C repro on 2025/09/09 09:36
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+ced9ca7ff40e0d3ad40f@syzkaller.appspotmail.com
First crash: 97d, last: 1d11h
Bug presence (2)
Date Name Commit Repro Result
2025/12/14 linux-6.6.y (ToT) 5fa4793a2d2d C [report] INFO: task hung in uhid_char_release
2025/12/14 upstream (ToT) 4a298a43f5e3 C Didn't crash
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in uhid_char_release input 1 C done done 479 121d 905d 0/29 upstream: reported C repro on 2023/06/24 03:16
android-6-12 INFO: task hung in uhid_char_release origin:upstream 1 C 12 41d 179d 0/1 premoderation: reported C repro on 2025/06/19 10:50

Sample crash report:
INFO: task syz.3.20:6017 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.20        state:D
 stack:25544 pid:6017  ppid:5912   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 schedule_timeout+0x9b/0x280 kernel/time/timer.c:2144
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common kernel/sched/completion.c:116 [inline]
 wait_for_common kernel/sched/completion.c:127 [inline]
 wait_for_completion+0x2bd/0x590 kernel/sched/completion.c:148
 __flush_work+0x895/0x9f0 kernel/workqueue.c:3430
 __cancel_work_timer+0x3b0/0x520 kernel/workqueue.c:3517
 uhid_dev_destroy drivers/hid/uhid.c:585 [inline]
 uhid_char_release+0xaf/0x600 drivers/hid/uhid.c:663
 __fput+0x234/0x970 fs/file_table.c:384
 task_work_run+0x1ce/0x250 kernel/task_work.c:239
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xf6/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f82f1d8f749
RSP: 002b:00007fff93471cc8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 000000000002d126 RCX: 00007f82f1d8f749
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f82f1fe7da0 R08: 0000000000000001 R09: 0000000293471fbf
R10: 0000001b2d020000 R11: 0000000000000246 R12: 00007f82f1fe5fac
R13: 00007f82f1fe5fa0 R14: ffffffffffffffff R15: 00007fff93471de0
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/1:0/23:
1 lock held by khungtaskd/29:
 #0: 
ffffffff8cd2ff20
 (
rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
3 locks held by kworker/u4:2/42:
2 locks held by kworker/1:2/786:
 #0: ffff888017872538 (
(wq_completion)rcu_gp
){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
 #1: ffffc90003b47d00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
 #1: ffffc90003b47d00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
3 locks held by kworker/0:2/787:
6 locks held by kworker/u4:9/3465:
 #0: ffff888017873938 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
 #0: ffff888017873938 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
 #1: ffffc9000d217d00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
 #1: ffffc9000d217d00 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
 #2: ffffffff8dfa8610 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x136/0xb90 net/core/net_namespace.c:606
 #3: ffffffff8dfb5448 (rtnl_mutex){+.+.}-{3:3}, at: caif_exit_net+0x6a/0x4b0 net/caif/caif_dev.c:527
 #4: ffff888025da8480 (&caifn->caifdevs.lock){+.+.}-{3:3}, at: caif_exit_net+0x7d/0x4b0 net/caif/caif_dev.c:528
 #5: ffffffff8cd358f8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:324 [inline]
 #5: ffffffff8cd358f8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x360/0x830 kernel/rcu/tree_exp.h:1004
2 locks held by getty/5525:
 #0: ffff8880312620a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000328b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x425/0x1380 drivers/tty/n_tty.c:2217
3 locks held by kworker/0:3/5749:
3 locks held by kworker/1:5/5973:
3 locks held by kworker/1:6/6011:
3 locks held by kworker/0:5/6014:
7 locks held by kworker/0:6/6077:
3 locks held by kworker/0:8/6103:
3 locks held by kworker/1:9/6266:
7 locks held by syz-executor/6285:
 #0: ffff88803179e418 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x20e/0x940 fs/read_write.c:580
 #1: ffff88805da37088 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e7/0x520 fs/kernfs/file.c:343
 #2: ffff88801ab09ca0 (kn->active#59){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #2: ffff88801ab09ca0 (kn->active#59){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x23a/0x520 fs/kernfs/file.c:344
 #3: ffffffff8d8984a8 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd2/0x360 drivers/net/netdevsim/bus.c:209
 #4: ffff88814727f0e8 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:995 [inline]
 #4: ffff88814727f0e8 (&dev->mutex){....}-{3:3}, at: __device_driver_lock drivers/base/dd.c:1095 [inline]
 #4: ffff88814727f0e8 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal+0xb6/0x7a0 drivers/base/dd.c:1292
 #5: ffff8880268b0250 (&devlink->lock_key#3){+.+.}-{3:3}, at: nsim_drv_remove+0x50/0x160 drivers/net/netdevsim/dev.c:1675
 #6: ffffffff8dfb5448 (rtnl_mutex){+.+.}-{3:3}, at: nsim_destroy+0x3f/0x180 drivers/net/netdevsim/netdev.c:417
1 lock held by syz-executor/6310:
 #0: ffffffff8dfb5448 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:78 [inline]
 #0: ffffffff8dfb5448 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x76f/0xf10 net/core/rtnetlink.c:6469
1 lock held by syz-executor/6314:
 #0: ffffffff8dfb5448 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:78 [inline]
 #0: ffffffff8dfb5448 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x76f/0xf10 net/core/rtnetlink.c:6469
1 lock held by syz-executor/6315:
 #0: ffffffff8dfb5448 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:78 [inline]
 #0: ffffffff8dfb5448 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x76f/0xf10 net/core/rtnetlink.c:6469

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

NMI backtrace for cpu 1
CPU: 1 PID: 29 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x39b/0x3d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x2f0 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
 watchdog+0xf41/0xf80 kernel/hung_task.c:379
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 6077 Comm: kworker/0:6 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: events uhid_device_add_worker
RIP: 0010:check_kcov_mode kernel/kcov.c:182 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:245 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp8+0x17/0x80 kernel/kcov.c:320
Code: 48 89 44 11 20 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 f3 0f 1e fa 48 8b 04 24 65 48 8b 0d b0 20 7e 7e 65 8b 15 b1 20 7e 7e <81> e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 57 83 b9 1c 16 00 00
RSP: 0018:ffffc90000007400 EFLAGS: 00000246
RAX: ffffffff81321d9a RBX: ffffc900000074c0 RCX: ffff888027938000
RDX: 0000000000000102 RSI: ffffffff816a5e39 RDI: 0000000000000000
RBP: ffffc90000007490 R08: ffff888027938000 R09: 0000000000000003
R10: 0000000000000004 R11: 0000000000000100 R12: ffffffff816a5e39
R13: 00000000000002c0 R14: ffffffff81746d20 R15: ffffc90000007408
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000560726525a30 CR3: 000000000cb30000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 arch_stack_walk+0x12a/0x190 arch/x86/kernel/stacktrace.c:27
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:328
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3495 [inline]
 kmem_cache_alloc_node+0x150/0x330 mm/slub.c:3540
 kmalloc_reserve+0x95/0x240 net/core/skbuff.c:562
 __alloc_skb+0x138/0x2c0 net/core/skbuff.c:653
 skb_copy+0x13d/0x7a0 net/core/skbuff.c:1987
 mac80211_hwsim_tx_frame_no_nl+0xc81/0x1170 drivers/net/wireless/virtual/mac80211_hwsim.c:1840
 mac80211_hwsim_tx_frame+0x1b5/0x200 drivers/net/wireless/virtual/mac80211_hwsim.c:2176
 mac80211_hwsim_beacon_tx+0x3e9/0x780 drivers/net/wireless/virtual/mac80211_hwsim.c:2269
 __iterate_interfaces+0x243/0x500 net/mac80211/util.c:766
 ieee80211_iterate_active_interfaces_atomic+0xdb/0x180 net/mac80211/util.c:802
 mac80211_hwsim_beacon+0xbb/0x1b0 drivers/net/wireless/virtual/mac80211_hwsim.c:2295
 __run_hrtimer kernel/time/hrtimer.c:1750 [inline]
 __hrtimer_run_queues+0x51e/0xc40 kernel/time/hrtimer.c:1814
 hrtimer_run_softirq+0x187/0x2b0 kernel/time/hrtimer.c:1831
 handle_softirqs+0x280/0x820 kernel/softirq.c:578
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xc7/0x190 kernel/softirq.c:661
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:console_flush_all+0x889/0xd00 arch/x86/include/asm/irqflags.h:-1
Code: ed 01 00 00 e8 a8 32 1b 00 4d 85 ff 48 8b 5c 24 38 75 07 e8 99 32 1b 00 eb 06 e8 92 32 1b 00 fb 49 bf 00 00 00 00 00 fc ff df <48> 8b 44 24 50 42 0f b6 04 38 84 c0 0f 85 2f 02 00 00 80 3b 01 0f
RSP: 0018:ffffc90003b16f40 EFLAGS: 00000293
RAX: ffffffff816a5e2e RBX: ffffc90003b170df RCX: ffff888027938000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90003b170b0 R08: ffffffff90d94507 R09: 1ffffffff21b28a0
R10: dffffc0000000000 R11: fffffbfff21b28a1 R12: ffffffff8d4b52e0
R13: 1ffffffff19792f8 R14: ffffffff8d4b5338 R15: dffffc0000000000
 console_unlock+0xae/0x340 kernel/printk/printk.c:3069
 vprintk_emit+0x477/0x600 kernel/printk/printk.c:2341
 dev_vprintk_emit+0x338/0x3e0 drivers/base/core.c:4953
 dev_printk_emit+0xe1/0x130 drivers/base/core.c:4964
 _dev_warn+0x10b/0x160 drivers/base/core.c:5020
 hid_parser_main+0x83b/0xbf0 drivers/hid/hid-core.c:632
 hid_open_report+0x853/0xec0 drivers/hid/hid-core.c:1278
 hid_parse include/linux/hid.h:1122 [inline]
 hid_generic_probe+0x3d/0x80 drivers/hid/hid-generic.c:66
 __hid_device_probe drivers/hid/hid-core.c:2649 [inline]
 hid_device_probe+0x293/0x5b0 drivers/hid/hid-core.c:2686
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x25b/0xb40 drivers/base/dd.c:658
 __driver_probe_device+0x18c/0x330 drivers/base/dd.c:800
 driver_probe_device+0x4f/0x420 drivers/base/dd.c:830
 __device_attach_driver+0x2ca/0x520 drivers/base/dd.c:958
 bus_for_each_drv+0x24b/0x2d0 drivers/base/bus.c:459
 __device_attach+0x2b5/0x400 drivers/base/dd.c:1030
 bus_probe_device+0x180/0x260 drivers/base/bus.c:534
 device_add+0x85b/0xc20 drivers/base/core.c:3683
 hid_add_device+0x38d/0x530 drivers/hid/hid-core.c:2832
 uhid_device_add_worker+0x43/0xe0 drivers/hid/uhid.c:73
 process_one_work kernel/workqueue.c:2634 [inline]
 process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/13 21:26 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in uhid_char_release
2025/11/22 14:14 linux-6.6.y 0a805b6ea8cd 4fb8ef37 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in uhid_char_release
2025/09/11 14:29 linux-6.6.y fe9731e10004 fdeaa69b .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in uhid_char_release
2025/09/11 12:58 linux-6.6.y fe9731e10004 fdeaa69b .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in uhid_char_release
2025/09/09 09:35 linux-6.6.y 355bd0b51d2f d291dd2d .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in uhid_char_release
2025/12/13 16:23 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in uhid_char_release
2025/11/22 06:24 linux-6.6.y 0a805b6ea8cd 4fb8ef37 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in uhid_char_release
* Struck through repros no longer work on HEAD.