syzbot


INFO: task hung in commit_echoes (6)

Status: auto-obsoleted due to no activity on 2025/08/21 17:16
Subsystems: serial
[Documentation on labels]
First crash: 96d, last: 96d
Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in commit_echoes serial 1 1 2615d 2611d 8/29 fixed on 2018/07/09 18:05
android-49 INFO: task hung in commit_echoes 1 C 44 2607d 2330d 0/3 public: reported C repro on 2019/04/11 08:44
upstream INFO: task hung in commit_echoes (2) serial 1 3 1798d 1835d 0/29 auto-closed as invalid on 2020/12/23 20:14
upstream INFO: task hung in commit_echoes (4) serial 1 1 830d 830d 0/29 auto-obsoleted due to no activity on 2023/07/19 08:09
upstream INFO: task hung in commit_echoes (5) serial 1 2 205d 218d 0/29 auto-obsoleted due to no activity on 2025/05/04 22:28
linux-4.19 INFO: task hung in commit_echoes 1 1 2067d 2067d 0/1 auto-closed as invalid on 2020/04/28 11:37
upstream INFO: task hung in commit_echoes (3) serial 1 3 1118d 1213d 0/29 auto-obsoleted due to no activity on 2022/11/03 18:56

Sample crash report:
INFO: task kworker/u8:8:2972 blocked for more than 144 seconds.
      Not tainted 6.15.0-rc7-syzkaller-00112-geccf6f2f6ab9 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:8    state:D stack:21848 pid:2972  tgid:2972  ppid:2      task_flags:0x4208060 flags:0x00004000
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x116f/0x5de0 kernel/sched/core.c:6767
 __schedule_loop kernel/sched/core.c:6845 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:6860
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6917
 __mutex_lock_common kernel/locking/mutex.c:678 [inline]
 __mutex_lock+0x6c7/0xb90 kernel/locking/mutex.c:746
 commit_echoes+0x4c/0x210 drivers/tty/n_tty.c:740
 n_tty_receive_char+0x3d7/0x600 drivers/tty/n_tty.c:1421
 n_tty_receive_buf_standard+0x6aa/0x3140 drivers/tty/n_tty.c:1590
 __receive_buf drivers/tty/n_tty.c:1624 [inline]
 n_tty_receive_buf_common+0x8eb/0x1980 drivers/tty/n_tty.c:1723
 tty_ldisc_receive_buf+0xa7/0x1a0 drivers/tty/tty_buffer.c:387
 tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:445 [inline]
 flush_to_ldisc+0x26b/0x780 drivers/tty/tty_buffer.c:495
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3319 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3400
 kthread+0x3c2/0x780 kernel/kthread.c:464
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Showing all locks held in the system:
1 lock held by kthreadd/2:
2 locks held by kworker/0:1/10:
4 locks held by kworker/u8:0/12:
 #0: ffff88802a11d948 ((wq_completion)wg-kex-wg1#3){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3213
 #1: ffffc90000117d18 ((work_completion)(&peer->transmit_handshake_work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3214
 #2: ffff88805cb51308 (&wg->static_identity.lock){++++}-{4:4}, at: wg_noise_handshake_create_initiation+0xec/0x650 drivers/net/wireguard/noise.c:529
 #3: ffff88805b456648 (&handshake->lock){++++}-{4:4}, at: wg_noise_handshake_create_initiation+0x100/0x650 drivers/net/wireguard/noise.c:530
4 locks held by kworker/u8:1/13:
2 locks held by kworker/1:0/24:
1 lock held by khungtaskd/31:
 #0: ffffffff8e3bfc00 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8e3bfc00 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8e3bfc00 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x36/0x1c0 kernel/locking/lockdep.c:6764
4 locks held by kworker/u8:2/36:
3 locks held by kworker/1:1/47:
 #0: ffff88805cac5148 ((wq_completion)wg-kex-wg2#4){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3213
 #1: ffffc90000b87d18 ((work_completion)(&({ do { const void *__vpp_verify = (typeof((worker) + 0))((void *)0); (void)__vpp_verify; } while (0); ({ unsigned long __ptr; __asm__ ("" : "=r"(__ptr) : "0"((__typeof__(*((worker))) *)(( unsigned long)((worker))))); (typeof((__typeof__(*((worker))) *)(( unsigned long)((worker))))) (__ptr + (((__per_cpu_offset[(cpu)])))); }); })->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3214
 #2: ffff888032628338 (&handshake->lock){++++}-{4:4}, at: wg_noise_handshake_begin_session+0x30/0xe80 drivers/net/wireguard/noise.c:822
6 locks held by kworker/u8:5/557:
4 locks held by kworker/u8:6/1321:
6 locks held by kworker/u8:8/2972:
 #0: ffff88801b481148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3213
 #1: ffffc9000c24fd18 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3214
 #2: ffff88801b4990b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x780 drivers/tty/tty_buffer.c:467
 #3: ffff88805cd0c0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x1c/0x80 drivers/tty/tty_ldisc.c:263
 #4: ffff88805cd0c2e8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_receive_buf_common+0x85/0x1980 drivers/tty/n_tty.c:1686
 #5: ffffc9000425b380 (&ldata->output_lock){+.+.}-{4:4}, at: commit_echoes+0x4c/0x210 drivers/tty/n_tty.c:740
3 locks held by kworker/u8:9/3015:
4 locks held by kworker/R-bat_e/3394:
1 lock held by klogd/5173:
2 locks held by udevd/5184:
2 locks held by dhcpcd/5478:
5 locks held by dhcpcd/5479:
2 locks held by getty/5576:
 #0: ffff888035fa20a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc900033332f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x41b/0x14f0 drivers/tty/n_tty.c:2222
1 lock held by syz-executor/5797:
5 locks held by syz-executor/5854:
2 locks held by syz-executor/5856:
1 lock held by syz-executor/5858:
2 locks held by syz-executor/5859:
3 locks held by kworker/1:2/5863:
 #0: ffff88801b478d48 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3213
 #1: ffffc9000476fd18 ((work_completion)(&(&ovs_net->masks_rebalance)->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3214
 #2: ffffffff9063b1e8 (ovs_mutex){+.+.}-{4:4}, at: ovs_lock net/openvswitch/datapath.c:108 [inline]
 #2: ffffffff9063b1e8 (ovs_mutex){+.+.}-{4:4}, at: ovs_dp_masks_rebalance+0x24/0xf0 net/openvswitch/datapath.c:2531
4 locks held by kworker/0:4/5900:
4 locks held by kworker/0:6/5902:
4 locks held by kworker/1:4/5928:
 #0: ffff888029085148 ((wq_completion)wg-kex-wg1#4){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3213
 #1: ffffc900055efd18 ((work_completion)(&({ do { const void *__vpp_verify = (typeof((worker) + 0))((void *)0); (void)__vpp_verify; } while (0); ({ unsigned long __ptr; __asm__ ("" : "=r"(__ptr) : "0"((__typeof__(*((worker))) *)(( unsigned long)((worker))))); (typeof((__typeof__(*((worker))) *)(( unsigned long)((worker))))) (__ptr + (((__per_cpu_offset[(cpu)])))); }); })->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3214
 #2: ffff88805cb51308 (&wg->static_identity.lock){++++}-{4:4}, at: wg_noise_handshake_consume_initiation+0x1c2/0x880 drivers/net/wireguard/noise.c:598
 #3: ffff88805b456648 (&handshake->lock){++++}-{4:4}, at: wg_noise_handshake_consume_initiation+0x5ac/0x880 drivers/net/wireguard/noise.c:632
3 locks held by kworker/1:5/5931:
 #0: ffff88801b478d48 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3213
 #1: ffffc9000560fd18 ((work_completion)(&(&ovs_net->masks_rebalance)->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3214
 #2: ffffffff9063b1e8 (ovs_mutex){+.+.}-{4:4}, at: ovs_lock net/openvswitch/datapath.c:108 [inline]
 #2: ffffffff9063b1e8 (ovs_mutex){+.+.}-{4:4}, at: ovs_dp_masks_rebalance+0x24/0xf0 net/openvswitch/datapath.c:2531
3 locks held by kworker/1:6/5949:
 #0: ffff88801b478d48 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3213
 #1: ffffc9000567fd18 ((work_completion)(&(&ovs_net->masks_rebalance)->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3214
 #2: ffffffff9063b1e8 (ovs_mutex){+.+.}-{4:4}, at: ovs_lock net/openvswitch/datapath.c:108 [inline]
 #2: ffffffff9063b1e8 (ovs_mutex){+.+.}-{4:4}, at: ovs_dp_masks_rebalance+0x24/0xf0 net/openvswitch/datapath.c:2531
6 locks held by syz.0.5213/16803:
4 locks held by kworker/u8:3/16971:
4 locks held by kworker/u8:4/16972:
2 locks held by kworker/u8:7/16974:
4 locks held by kworker/u8:10/16976:
4 locks held by kworker/u8:11/16977:
4 locks held by kworker/u8:12/16978:
4 locks held by kworker/u8:13/16979:
4 locks held by kworker/u8:14/16980:

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 31 Comm: khungtaskd Not tainted 6.15.0-rc7-syzkaller-00112-geccf6f2f6ab9 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x27b/0x390 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x29c/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:158 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:274 [inline]
 watchdog+0xf70/0x12c0 kernel/hung_task.c:437
 kthread+0x3c2/0x780 kernel/kthread.c:464
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 557 Comm: kworker/u8:5 Not tainted 6.15.0-rc7-syzkaller-00112-geccf6f2f6ab9 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: wg-kex-wg1 wg_packet_handshake_send_worker
RIP: 0010:__lock_acquire+0x117/0x1ba0 kernel/locking/lockdep.c:5144
Code: af c8 8b 44 24 08 48 8d 1c 80 48 89 4c 24 10 48 c1 e3 03 85 c0 74 25 f6 84 24 c8 00 00 00 01 75 1b 48 8d 74 2b d8 0f b7 46 20 <25> ff 1f 00 00 39 c8 75 09 4d 85 ff 0f 85 ef 05 00 00 48 01 eb 0f
RSP: 0018:ffffc90000a07750 EFLAGS: 00000046
RAX: 0000000000002007 RBX: 0000000000000118 RCX: 0000000000000007
RDX: 0000000000000000 RSI: ffff888024fad460 RDI: ffffffff8e3bfc00
RBP: ffff888024fad370 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: ffffffff8e3bfc00 R12: 0000000000000000
R13: 0000000000000002 R14: ffff888024fac880 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff888124ada000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7acaa00000 CR3: 000000005ed8c000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 lock_acquire kernel/locking/lockdep.c:5866 [inline]
 lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823
 rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 rcu_read_lock include/linux/rcupdate.h:841 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1155 [inline]
 unwind_next_frame+0xd1/0x20a0 arch/x86/kernel/unwind_orc.c:479
 arch_stack_walk+0x94/0x100 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2380 [inline]
 slab_free mm/slub.c:4642 [inline]
 kmem_cache_free+0x2d4/0x4d0 mm/slub.c:4744
 __skb_ext_put+0x102/0x2c0 net/core/skbuff.c:7128
 __skb_ext_del+0xf3/0x340 net/core/skbuff.c:7095
 skb_ext_del include/linux/skbuff.h:4895 [inline]
 nf_bridge_info_free net/bridge/br_netfilter_hooks.c:156 [inline]
 br_nf_dev_queue_xmit+0x7b7/0x2cb0 net/bridge/br_netfilter_hooks.c:922
 NF_HOOK include/linux/netfilter.h:314 [inline]
 NF_HOOK include/linux/netfilter.h:308 [inline]
 br_nf_post_routing+0x8e7/0x1190 net/bridge/br_netfilter_hooks.c:969
 nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline]
 nf_hook_slow+0xbb/0x200 net/netfilter/core.c:626
 nf_hook+0x45e/0x780 include/linux/netfilter.h:269
 NF_HOOK include/linux/netfilter.h:312 [inline]
 br_forward_finish+0xcd/0x130 net/bridge/br_forward.c:66
 br_nf_hook_thresh+0x304/0x410 net/bridge/br_netfilter_hooks.c:1170
 br_nf_forward_finish+0x66a/0xba0 net/bridge/br_netfilter_hooks.c:665
 NF_HOOK include/linux/netfilter.h:314 [inline]
 NF_HOOK include/linux/netfilter.h:308 [inline]
 br_nf_forward_ip.part.0+0x609/0x810 net/bridge/br_netfilter_hooks.c:719
 br_nf_forward_ip net/bridge/br_netfilter_hooks.c:679 [inline]
 br_nf_forward+0xf0f/0x1be0 net/bridge/br_netfilter_hooks.c:776
 nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline]
 nf_hook_slow+0xbb/0x200 net/netfilter/core.c:626
 nf_hook+0x45e/0x780 include/linux/netfilter.h:269
 NF_HOOK include/linux/netfilter.h:312 [inline]
 __br_forward+0x1be/0x5b0 net/bridge/br_forward.c:115
 deliver_clone net/bridge/br_forward.c:131 [inline]
 br_flood+0x39c/0x650 net/bridge/br_forward.c:249
 br_handle_frame_finish+0xe8e/0x1c20 net/bridge/br_input.c:220
 br_nf_hook_thresh+0x304/0x410 net/bridge/br_netfilter_hooks.c:1170
 br_nf_pre_routing_finish_ipv6+0x76a/0xfb0 net/bridge/br_netfilter_ipv6.c:154
 NF_HOOK include/linux/netfilter.h:314 [inline]
 br_nf_pre_routing_ipv6+0x3cd/0x8c0 net/bridge/br_netfilter_ipv6.c:184
 br_nf_pre_routing+0x860/0x15b0 net/bridge/br_netfilter_hooks.c:508
 nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:282 [inline]
 br_handle_frame+0xad8/0x14b0 net/bridge/br_input.c:433
 __netif_receive_skb_core.constprop.0+0xa26/0x4a00 net/core/dev.c:5773
 __netif_receive_skb_one_core+0xb0/0x1e0 net/core/dev.c:5885
 __netif_receive_skb+0x1d/0x160 net/core/dev.c:6000
 process_backlog+0x442/0x15e0 net/core/dev.c:6352
 __napi_poll.constprop.0+0xba/0x550 net/core/dev.c:7324
 napi_poll net/core/dev.c:7388 [inline]
 net_rx_action+0xa97/0x1010 net/core/dev.c:7510
 handle_softirqs+0x216/0x8e0 kernel/softirq.c:579
 do_softirq kernel/softirq.c:480 [inline]
 do_softirq+0xb2/0xf0 kernel/softirq.c:467
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x100/0x120 kernel/softirq.c:407
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 fpregs_unlock arch/x86/include/asm/fpu/api.h:77 [inline]
 kernel_fpu_end+0x5e/0x70 arch/x86/kernel/fpu/core.c:460
 blake2s_compress+0x7f/0xe0 arch/x86/crypto/blake2s-glue.c:49
 blake2s_update+0xef/0x360 lib/crypto/blake2s.c:32
 hmac.constprop.0+0x23f/0x420 drivers/net/wireguard/noise.c:324
 kdf.constprop.0+0x1a1/0x280 drivers/net/wireguard/noise.c:375
 mix_precomputed_dh drivers/net/wireguard/noise.c:426 [inline]
 wg_noise_handshake_create_initiation+0x3b0/0x650 drivers/net/wireguard/noise.c:560
 wg_packet_send_handshake_initiation+0x19a/0x360 drivers/net/wireguard/send.c:34
 wg_packet_handshake_send_worker+0x1c/0x30 drivers/net/wireguard/send.c:51
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3319 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3400
 kthread+0x3c2/0x780 kernel/kthread.c:464
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/05/23 17:15 upstream eccf6f2f6ab9 f8cc0c83 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: task hung in commit_echoes
* Struck through repros no longer work on HEAD.