INFO: task hung in htable_put (3)

Status: upstream: reported on 2026/08/01 09:09
Reported-by: syzbot+dc2423082b59685d9efa@syzkaller.appspotmail.com
First crash: 6d10h, last: 6d10h
▶ ▼ Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 INFO: task hung in htable_put 1 3 378d 414d 0/2 auto-obsoleted due to no activity on 2025/11/01 23:35
upstream INFO: task hung in htable_put 1 syz, C done done 29 2362d 2415d 15/29 fixed on 2020/11/16 12:12
linux-4.19 INFO: task hung in htable_put 1 syz, C done 8 2357d 2403d 1/1 fixed on 2020/03/24 16:08
upstream INFO: task hung in htable_put (2) kernel 1 54 561d 621d 0/29 auto-obsoleted due to no activity on 2025/04/03 01:38
linux-6.6 INFO: task hung in htable_put (2) 1 1 149d 149d 0/2 auto-obsoleted due to no activity on 2026/06/19 02:51
linux-4.19 INFO: task hung in htable_put (2) 1 1 1983d 1983d 0/1 auto-closed as invalid on 2021/07/01 18:58

Sample crash report:
INFO: task syz.2.129:6171 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.129       state:D stack:26512 pid:6171  ppid:5774   flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 schedule_timeout+0xc1/0x2d0 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+0x2c6/0x5a0 kernel/sched/completion.c:148
 __flush_work+0x92f/0xac0 kernel/workqueue.c:3471
 __cancel_work_timer+0x3f8/0x560 kernel/workqueue.c:3558
 htable_put+0x1c4/0x230 net/netfilter/xt_hashlimit.c:429
 cleanup_match net/ipv6/netfilter/ip6_tables.c:477 [inline]
 cleanup_entry+0x15a/0x350 net/ipv6/netfilter/ip6_tables.c:661
 translate_table+0x1e04/0x2020 net/ipv6/netfilter/ip6_tables.c:744
 do_replace net/ipv6/netfilter/ip6_tables.c:1152 [inline]
 do_ip6t_set_ctl+0x9fe/0xe10 net/ipv6/netfilter/ip6_tables.c:1641
 nf_setsockopt+0x263/0x280 net/netfilter/nf_sockopt.c:101
 rawv6_setsockopt+0x276/0x5d0 net/ipv6/raw.c:1048
 do_sock_setsockopt+0x175/0x1a0 net/socket.c:2322
 __sys_setsockopt net/socket.c:2345 [inline]
 __do_sys_setsockopt net/socket.c:2354 [inline]
 __se_sys_setsockopt net/socket.c:2351 [inline]
 __x64_sys_setsockopt+0x182/0x200 net/socket.c:2351
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f2ed839e019
RSP: 002b:00007f2ed91f9028 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007f2ed8625fa0 RCX: 00007f2ed839e019
RDX: 0000000000000040 RSI: 0000000000000029 RDI: 0000000000000003
RBP: 00007f2ed843500c R08: 0000000000000528 R09: 0000000000000000
R10: 00002000000014c0 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2ed8626038 R14: 00007f2ed8625fa0 R15: 00007ffc22b2f218
 </TASK>

Showing all locks held in the system:
2 locks held by kworker/0:0/8:
4 locks held by kworker/0:1/9:
1 lock held by khungtaskd/28:
 #0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
2 locks held by kworker/u4:4/59:
 #0: ffff888017c71538 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #0: ffff888017c71538 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
 #1: ffffc900015a7d00 (connector_reaper_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #1: ffffc900015a7d00 (connector_reaper_work){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
2 locks held by kworker/0:2/173:
3 locks held by kworker/1:2/789:
 #0: ffff888017c71d38 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #0: ffff888017c71d38 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
 #1: ffffc90003a4fd00 ((reg_check_chans).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #1: ffffc90003a4fd00 ((reg_check_chans).work){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
 #2: ffffffff8e3d6b08 (rtnl_mutex){+.+.}-{3:3}, at: reg_check_chans_work+0x92/0xd90 net/wireless/reg.c:2463
3 locks held by kworker/u4:6/1117:
 #0: ffff888017c71538 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #0: ffff888017c71538 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
 #1: ffffc900045f7d00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #1: ffffc900045f7d00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
 #2: ffffffff8e3d6b08 (rtnl_mutex){+.+.}-{3:3}, at: linkwatch_event+0xe/0x60 net/core/link_watch.c:286
2 locks held by kworker/u4:7/1136:
 #0: ffff8880b8f3c298 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x29/0x130 kernel/sched/core.c:559
 #1: ffff8880b8f28a00 (psi_seq){-.-.}-{0:0}, at: psi_sched_switch kernel/sched/stats.h:189 [inline]
 #1: ffff8880b8f28a00 (psi_seq){-.-.}-{0:0}, at: __schedule+0x21d3/0x4660 kernel/sched/core.c:6696
2 locks held by kworker/u4:8/4753:
 #0: ffff888017c71538 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #0: ffff888017c71538 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
 #1: ffffc9000fb0fd00 ((reaper_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #1: ffffc9000fb0fd00 ((reaper_work).work){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
2 locks held by kworker/u4:9/4764:
1 lock held by klogd/5129:
1 lock held by dhcpcd/5435:
 #0: ffffffff8e3d6b08 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:78 [inline]
 #0: ffffffff8e3d6b08 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x7ed/0xf90 net/core/rtnetlink.c:6481
2 locks held by getty/5530:
 #0: ffff88814df300a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc900032832f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x428/0x1370 drivers/tty/n_tty.c:2217
3 locks held by kworker/u4:12/6207:
 #0: ffff88814c9db938 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #0: ffff88814c9db938 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
 #1: ffffc9000bc27d00 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #1: ffffc9000bc27d00 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
 #2: ffffffff8e3d6b08 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_verify_work+0x19/0x30 net/ipv6/addrconf.c:4730
4 locks held by kworker/u4:14/6209:
 #0: ffff88801a25c938 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #0: ffff88801a25c938 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
 #1: ffffc9000c7afd00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #1: ffffc9000c7afd00 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
 #2: ffffffff8e3c9b10 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x14c/0xbb0 net/core/net_namespace.c:606
 #3: ffffffff8e3d6b08 (rtnl_mutex){+.+.}-{3:3}, at: wg_destruct+0x25/0x310 drivers/net/wireguard/device.c:247
2 locks held by kworker/0:7/6712:
4 locks held by syz.5.231/6776:
 #0: ffffffff8e43baf0 (cb_lock){++++}-{3:3}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1074
 #1: ffffffff8e43b908 (genl_mutex){+.+.}-{3:3}, at: genl_lock net/netlink/genetlink.c:33 [inline]
 #1: ffffffff8e43b908 (genl_mutex){+.+.}-{3:3}, at: genl_op_lock net/netlink/genetlink.c:58 [inline]
 #1: ffffffff8e43b908 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0x10c/0x7a0 net/netlink/genetlink.c:1065
 #2: ffffffff8e3d6b08 (rtnl_mutex){+.+.}-{3:3}, at: wg_set_device+0xf8/0x1fb0 drivers/net/wireguard/netlink.c:504
 #3: ffff888079821468 (&wg->device_update_lock){+.+.}-{3:3}, at: wg_set_device+0x110/0x1fb0 drivers/net/wireguard/netlink.c:505
2 locks held by syz.5.231/6777:
 #0: ffffffff8e43baf0 (cb_lock){++++}-{3:3}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1074
 #1: ffffffff8e43b908 (genl_mutex){+.+.}-{3:3}, at: genl_lock net/netlink/genetlink.c:33 [inline]
 #1: ffffffff8e43b908 (genl_mutex){+.+.}-{3:3}, at: genl_op_lock net/netlink/genetlink.c:58 [inline]
 #1: ffffffff8e43b908 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0x10c/0x7a0 net/netlink/genetlink.c:1065
1 lock held by syz-executor/6779:
 #0: ffffffff8e3d6b08 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:78 [inline]
 #0: ffffffff8e3d6b08 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x7ed/0xf90 net/core/rtnetlink.c:6481
1 lock held by syz-executor/6782:
 #0: ffffffff8e3d6b08 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:78 [inline]
 #0: ffffffff8e3d6b08 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x7ed/0xf90 net/core/rtnetlink.c:6481
1 lock held by syz-executor/6785:
 #0: ffffffff8e3d6b08 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:78 [inline]
 #0: ffffffff8e3d6b08 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x7ed/0xf90 net/core/rtnetlink.c:6481
1 lock held by syz-executor/6788:
 #0: ffffffff8e3d6b08 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:78 [inline]
 #0: ffffffff8e3d6b08 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x7ed/0xf90 net/core/rtnetlink.c:6481

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

NMI backtrace for cpu 1
CPU: 1 PID: 28 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a6/0x3e0 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+0xf59/0xfa0 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: 173 Comm: kworker/0:2 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: events_power_efficient htable_gc
RIP: 0010:check_preemption_disabled+0x13/0x110 lib/smp_processor_id.c:13
Code: 1d 8b 48 c7 c6 40 06 1d 8b eb 0c 66 2e 0f 1f 84 00 00 00 00 00 66 90 55 41 57 41 56 53 48 83 ec 10 65 48 8b 04 25 28 00 00 00 <48> 89 44 24 08 65 8b 05 9d dd 76 75 65 8b 0d 92 dd 76 75 f7 c1 ff
RSP: 0000:ffffc900000077e8 EFLAGS: 00000286
RAX: 126a6bc9ec694600 RBX: dffffc0000000000 RCX: ffff88801bbdda00
RDX: 0000000000000100 RSI: ffffffff8bcfbd20 RDI: ffffffff8b1d0660
RBP: ffffc90000007a00 R08: ffffc9000000797f R09: 0000000000000000
R10: ffffc90000007960 R11: fffff52000000f30 R12: 1ffff92000000f28
R13: 0000000000000001 R14: ffff88803152e840 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f15d17fef40 CR3: 000000000cf32000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 xt_write_recseq_end include/linux/netfilter/x_tables.h:397 [inline]
 ipt_do_table+0x1393/0x15c0 net/ipv4/netfilter/ip_tables.c:356
 nf_hook_entry_hookfn include/linux/netfilter.h:144 [inline]
 nf_hook_slow+0xbd/0x200 net/netfilter/core.c:626
 nf_hook include/linux/netfilter.h:259 [inline]
 NF_HOOK+0x21d/0x3b0 include/linux/netfilter.h:302
 __netif_receive_skb_one_core net/core/dev.c:5646 [inline]
 __netif_receive_skb+0xcc/0x290 net/core/dev.c:5760
 process_backlog+0x380/0x710 net/core/dev.c:6088
 __napi_poll+0xbb/0x460 net/core/dev.c:6650
 napi_poll net/core/dev.c:6717 [inline]
 net_rx_action+0x65f/0xcc0 net/core/dev.c:6853
 handle_softirqs+0x27d/0x820 kernel/softirq.c:578
 do_softirq+0xfa/0x1a0 kernel/softirq.c:479
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x184/0x1c0 kernel/softirq.c:406
 spin_unlock_bh include/linux/spinlock.h:396 [inline]
 htable_selective_cleanup+0x26a/0x300 net/netfilter/xt_hashlimit.c:374
 htable_gc+0x29/0xa0 net/netfilter/xt_hashlimit.c:385
 process_one_work kernel/workqueue.c:2653 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2730
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2811
 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 (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/01 09:08 linux-6.6.y a1153c0deb44 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in htable_put
2026/08/01 09:08 linux-6.6.y a1153c0deb44 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in htable_put
* Struck through repros no longer work on HEAD.