syzbot


INFO: task hung in fb_open (3)

Status: auto-obsoleted due to no activity on 2025/07/05 02:15
Subsystems: fbdev
[Documentation on labels]
First crash: 106d, last: 106d
Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in fb_open 1 C done 552 1802d 2056d 0/29 closed as dup on 2020/07/27 23:07
linux-4.19 INFO: task hung in fb_open (2) 1 1 1596d 1596d 0/1 auto-closed as invalid on 2021/07/05 14:58
linux-4.19 INFO: task hung in fb_open 1 108 1818d 2055d 0/1 auto-closed as invalid on 2020/11/26 05:30
linux-4.14 INFO: task hung in fb_open 1 C error 241 1760d 2057d 0/1 upstream: reported C repro on 2019/12/03 09:19
upstream INFO: task hung in fb_open (2) fbdev 1 2 1760d 1760d 0/29 auto-closed as invalid on 2020/12/23 12:44

Sample crash report:
INFO: task syz.2.2124:10717 blocked for more than 143 seconds.
      Not tainted 6.14.0-syzkaller-13524-gf4d2ef48250a #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.2124      state:D stack:27912 pid:10717 tgid:10714 ppid:5835   task_flags:0x400040 flags:0x00000004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x1b88/0x5240 kernel/sched/core.c:6767
 __schedule_loop kernel/sched/core.c:6845 [inline]
 schedule+0x163/0x360 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+0x805/0x10c0 kernel/locking/mutex.c:746
 lock_fb_info include/linux/fb.h:627 [inline]
 fb_open+0xb1/0x2e0 drivers/video/fbdev/core/fb_chrdev.c:350
 chrdev_open+0x516/0x600 fs/char_dev.c:414
 do_dentry_open+0xdee/0x1960 fs/open.c:956
 vfs_open+0x3b/0x370 fs/open.c:1086
 do_open fs/namei.c:3845 [inline]
 path_openat+0x2caf/0x35d0 fs/namei.c:4004
 do_filp_open+0x284/0x4e0 fs/namei.c:4031
 do_sys_openat2+0x12b/0x1d0 fs/open.c:1429
 do_sys_open fs/open.c:1444 [inline]
 __do_sys_openat fs/open.c:1460 [inline]
 __se_sys_openat fs/open.c:1455 [inline]
 __x64_sys_openat+0x249/0x2a0 fs/open.c:1455
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f426cb8d169
RSP: 002b:00007f426da83038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f426cda5fa0 RCX: 00007f426cb8d169
RDX: 0000000000080000 RSI: 00002000000000c0 RDI: ffffffffffffff9c
RBP: 00007f426cc0e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007f426cda5fa0 R15: 00007ffd775edba8
 </TASK>

Showing all locks held in the system:
1 lock held by kthreadd/2:
3 locks held by kworker/u8:0/12:
3 locks held by kworker/u8:1/13:
1 lock held by khungtaskd/31:
 #0: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x30/0x180 kernel/locking/lockdep.c:6764
3 locks held by kworker/u8:2/36:
3 locks held by kworker/u8:3/52:
3 locks held by kworker/u8:4/55:
3 locks held by kworker/u8:5/82:
2 locks held by kworker/1:2/121:
4 locks held by kworker/u8:6/1037:
 #0: ffff88801bef6148 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3213 [inline]
 #0: ffff88801bef6148 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x990/0x18e0 kernel/workqueue.c:3319
 #1: ffffc90003adfc60 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3214 [inline]
 #1: ffffc90003adfc60 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x9cb/0x18e0 kernel/workqueue.c:3319
 #2: ffffffff900f0850 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0x17c/0xd60 net/core/net_namespace.c:608
 #3: ffffffff8ed433c0 (rcu_state.barrier_mutex){+.+.}-{4:4}, at: rcu_barrier+0x4c/0x530 kernel/rcu/tree.c:3774
2 locks held by kworker/R-bat_e/3397:
3 locks held by kworker/u8:7/4113:
2 locks held by syslogd/5188:
2 locks held by klogd/5195:
1 lock held by udevd/5206:
5 locks held by dhcpcd/5500:
2 locks held by getty/5592:
 #0: ffff88814d8090a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000332e2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x5bb/0x1700 drivers/tty/n_tty.c:2222
4 locks held by syz-executor/5821:
1 lock held by syz-executor/5834:
5 locks held by syz-executor/5838:
7 locks held by kworker/u9:2/5840:
 #0: ffff8880481f6148 ((wq_completion)hci7){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3213 [inline]
 #0: ffff8880481f6148 ((wq_completion)hci7){+.+.}-{0:0}, at: process_scheduled_works+0x990/0x18e0 kernel/workqueue.c:3319
 #1: ffffc900041cfc60 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3214 [inline]
 #1: ffffc900041cfc60 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_scheduled_works+0x9cb/0x18e0 kernel/workqueue.c:3319
 #2: ffff88805d93cd80 (&hdev->req_lock){+.+.}-{4:4}, at: hci_cmd_sync_work+0x1ec/0x400 net/bluetooth/hci_sync.c:331
 #3: ffff88805d93c078 (&hdev->lock){+.+.}-{4:4}, at: hci_abort_conn_sync+0x1f1/0xeb0 net/bluetooth/hci_sync.c:5597
 #4: ffffffff90263408 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_connect_cfm include/net/bluetooth/hci_core.h:2051 [inline]
 #4: ffffffff90263408 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_conn_failed+0x15d/0x300 net/bluetooth/hci_conn.c:1269
 #5: ffff888031e65b38 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_conn_del+0x71/0x690 net/bluetooth/l2cap_core.c:1761
 #6: ffffffff8ed434f8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock kernel/rcu/tree_exp.h:336 [inline]
 #6: ffffffff8ed434f8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x454/0x830 kernel/rcu/tree_exp.h:998
5 locks held by kworker/u9:5/5851:
 #0: ffff888059591948 ((wq_completion)hci6){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3213 [inline]
 #0: ffff888059591948 ((wq_completion)hci6){+.+.}-{0:0}, at: process_scheduled_works+0x990/0x18e0 kernel/workqueue.c:3319
 #1: ffffc9000426fc60 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3214 [inline]
 #1: ffffc9000426fc60 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_scheduled_works+0x9cb/0x18e0 kernel/workqueue.c:3319
 #2: ffff88805e478d80 (&hdev->req_lock){+.+.}-{4:4}, at: hci_cmd_sync_work+0x1ec/0x400 net/bluetooth/hci_sync.c:331
 #3: ffff88805e478078 (&hdev->lock){+.+.}-{4:4}, at: hci_abort_conn_sync+0x1f1/0xeb0 net/bluetooth/hci_sync.c:5597
 #4: ffffffff8ed434f8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock kernel/rcu/tree_exp.h:304 [inline]
 #4: ffffffff8ed434f8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x384/0x830 kernel/rcu/tree_exp.h:998
2 locks held by kworker/1:6/5931:
3 locks held by kworker/u8:8/6088:
4 locks held by kworker/0:9/10301:
3 locks held by kworker/u8:9/10466:
3 locks held by kworker/u8:10/10501:
8 locks held by syz.4.2042/10531:
1 lock held by syz.2.2124/10717:
 #0: ffff88802515c078 (&fb_info->lock){+.+.}-{4:4}, at: lock_fb_info include/linux/fb.h:627 [inline]
 #0: ffff88802515c078 (&fb_info->lock){+.+.}-{4:4}, at: fb_open+0xb1/0x2e0 drivers/video/fbdev/core/fb_chrdev.c:350
2 locks held by syz-executor/10729:
2 locks held by syz.6.2166/10856:
 #0: ffffffff8f58b2e8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2046 [inline]
 #0: ffffffff8f58b2e8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x234/0xde0 drivers/tty/tty_io.c:2129
 #1: ffff88805e4d71c0 (&tty->legacy_mutex){+.+.}-{4:4}, at: tty_init_dev+0x78/0x4c0 drivers/tty/tty_io.c:1415
3 locks held by kworker/u8:11/11036:
2 locks held by dhcpcd/11037:
3 locks held by kworker/u8:12/11038:
3 locks held by kworker/u8:13/11039:
3 locks held by kworker/u8:14/11040:
1 lock held by syz-executor/11041:
4 locks held by kworker/u8:15/11042:
3 locks held by kworker/u8:16/11043:
4 locks held by kworker/u8:17/11044:

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 31 Comm: khungtaskd Not tainted 6.14.0-syzkaller-13524-gf4d2ef48250a #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x4ab/0x4e0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x198/0x320 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+0x1058/0x10a0 kernel/hung_task.c:437
 kthread+0x7b9/0x940 kernel/kthread.c:464
 ret_from_fork+0x4d/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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 10301 Comm: kworker/0:9 Not tainted 6.14.0-syzkaller-13524-gf4d2ef48250a #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Workqueue: wg-kex-wg2 wg_packet_handshake_receive_worker
RIP: 0010:validate_xmit_skb+0xaac/0x1150 net/core/dev.c:3910
Code: 24 58 e8 77 08 d0 00 48 8b 4c 24 50 48 c7 44 24 60 0e 36 e0 45 49 c7 04 0f 00 00 00 00 65 49 8b 0c 24 48 3b 8c 24 a0 00 00 00 <0f> 85 90 06 00 00 48 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f 5d e9 16
RSP: 0018:ffffc90000006320 EFLAGS: 00000246
RAX: ffff8880956c8c80 RBX: 0000000000000000 RCX: ef4701d52a438c00
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000006410 R08: ffffffff8abb97ee R09: ffffffff89eb6b4e
R10: 0000000000000002 R11: ffff888025dd1e00 R12: ffffffff9368a020
R13: 0000000000000000 R14: ffff8880956c8c80 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff888124f96000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f365b8a9d8f CR3: 00000000617f8000 CR4: 0000000000350ef0
Call Trace:
 <IRQ>
 __dev_queue_xmit+0x17be/0x3f60 net/core/dev.c:4628
 dev_queue_xmit include/linux/netdevice.h:3350 [inline]
 br_dev_queue_push_xmit+0x771/0x950 net/bridge/br_forward.c:53
 NF_HOOK+0x6c1/0x780 include/linux/netfilter.h:314
 br_nf_post_routing+0xa28/0xe80 net/bridge/br_netfilter_hooks.c:969
 nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline]
 nf_hook_slow+0xca/0x220 net/netfilter/core.c:626
 nf_hook include/linux/netfilter.h:269 [inline]
 NF_HOOK+0x2ac/0x460 include/linux/netfilter.h:312
 br_forward_finish+0xd8/0x130 net/bridge/br_forward.c:66
 br_nf_hook_thresh net/bridge/br_netfilter_hooks.c:-1 [inline]
 br_nf_forward_finish+0xb50/0xfb0 net/bridge/br_netfilter_hooks.c:665
 NF_HOOK+0x6c1/0x780 include/linux/netfilter.h:314
 br_nf_forward_ip+0x61e/0x7b0 net/bridge/br_netfilter_hooks.c:719
 nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline]
 nf_hook_slow+0xca/0x220 net/netfilter/core.c:626
 nf_hook include/linux/netfilter.h:269 [inline]
 NF_HOOK+0x2ac/0x460 include/linux/netfilter.h:312
 __br_forward+0x46a/0x640 net/bridge/br_forward.c:115
 br_handle_frame_finish+0x185b/0x1f60 net/bridge/br_input.c:220
 br_nf_hook_thresh+0x484/0x5a0 net/bridge/br_netfilter_hooks.c:1170
 br_nf_pre_routing_finish_ipv6+0xaa3/0xdd0 net/bridge/br_netfilter_ipv6.c:-1
 NF_HOOK include/linux/netfilter.h:314 [inline]
 br_nf_pre_routing_ipv6+0x397/0x790 net/bridge/br_netfilter_ipv6.c:184
 nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:282 [inline]
 br_handle_frame+0x9fc/0x1530 net/bridge/br_input.c:433
 __netif_receive_skb_core+0x155c/0x4bb0 net/core/dev.c:5780
 __netif_receive_skb_one_core net/core/dev.c:5892 [inline]
 __netif_receive_skb+0x130/0x670 net/core/dev.c:6007
 process_backlog+0x664/0x15c0 net/core/dev.c:6359
 __napi_poll+0xcd/0x480 net/core/dev.c:7331
 napi_poll net/core/dev.c:7395 [inline]
 net_rx_action+0x89d/0x1240 net/core/dev.c:7517
 handle_softirqs+0x2d8/0x9b0 kernel/softirq.c:579
 do_softirq+0x11f/0x1e0 kernel/softirq.c:480
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x1be/0x200 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+0x103/0x150 arch/x86/kernel/fpu/core.c:460
 blake2s_compress+0x5f/0xd0 arch/x86/crypto/blake2s-glue.c:49
 blake2s_final+0x114/0x260 lib/crypto/blake2s.c:54
 hmac+0x674/0x9d0 drivers/net/wireguard/noise.c:333
 kdf+0xea/0x3a0 drivers/net/wireguard/noise.c:360
 mix_precomputed_dh drivers/net/wireguard/noise.c:426 [inline]
 wg_noise_handshake_consume_initiation+0x50b/0xd60 drivers/net/wireguard/noise.c:623
 wg_receive_handshake_packet drivers/net/wireguard/receive.c:144 [inline]
 wg_packet_handshake_receive_worker+0x5bd/0xf60 drivers/net/wireguard/receive.c:213
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xac5/0x18e0 kernel/workqueue.c:3319
 worker_thread+0x870/0xd50 kernel/workqueue.c:3400
 kthread+0x7b9/0x940 kernel/kthread.c:464
 ret_from_fork+0x4d/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
2025/04/06 02:07 upstream f4d2ef48250a 1c65791e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: task hung in fb_open
* Struck through repros no longer work on HEAD.