syzbot


INFO: task hung in do_fb_ioctl

Status: upstream: reported on 2025/07/27 03:50
Reported-by: syzbot+0b758f45db8c1912077a@syzkaller.appspotmail.com
First crash: 8d16h, last: 8d16h
Similar bugs (9)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in do_fb_ioctl (4) fbdev 1 1 813d 813d 0/29 auto-obsoleted due to no activity on 2023/07/13 16:33
upstream INFO: task hung in do_fb_ioctl (3) fbdev 1 2 1040d 1065d 0/29 auto-obsoleted due to no activity on 2023/01/02 23:29
upstream BUG: workqueue lockup (5) net 1 C done 13016 3h02m 2028d 0/29 upstream: reported C repro on 2020/01/14 22:04
upstream INFO: task hung in do_fb_ioctl (5) fbdev 1 1 320d 320d 0/29 auto-obsoleted due to no activity on 2024/12/17 19:15
upstream INFO: task hung in do_fb_ioctl (2) fbdev 1 1 1259d 1259d 0/29 auto-closed as invalid on 2022/05/22 20:52
linux-4.19 INFO: task hung in do_fb_ioctl 1 1 2034d 2034d 0/1 auto-closed as invalid on 2020/05/08 18:42
upstream INFO: task hung in do_fb_ioctl fbdev 1 47 1823d 2031d 0/29 closed as dup on 2020/07/27 22:56
linux-4.14 INFO: task hung in do_fb_ioctl 1 C error 24 1712d 2071d 0/1 upstream: reported C repro on 2019/12/03 05:09
linux-4.19 INFO: task hung in do_fb_ioctl (2) 1 C done 7 1443d 1858d 1/1 fixed on 2021/09/21 12:35

Sample crash report:
INFO: task syz.2.2791:14693 blocked for more than 143 seconds.
      Not tainted 6.1.147-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.2791      state:D stack:26336 pid:14693 ppid:4268   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x97/0x280 kernel/time/timer.c:1941
 ___down_common kernel/locking/semaphore.c:229 [inline]
 __down_common+0x2e7/0x700 kernel/locking/semaphore.c:250
 down+0x7c/0xd0 kernel/locking/semaphore.c:64
 console_lock+0x141/0x1c0 kernel/printk/printk.c:2629
 do_fb_ioctl+0x534/0x720 drivers/video/fbdev/core/fbmem.c:1123
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f472ad8e9a9
RSP: 002b:00007f472bba1038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f472afb5fa0 RCX: 00007f472ad8e9a9
RDX: 0000200000000040 RSI: 0000000000004601 RDI: 000000000000000a
RBP: 00007f472ae10d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f472afb5fa0 R15: 00007fffff25b998
 </TASK>

Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/12:
 #0: ffffffff8cb2b7b0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
 #0: ffffffff8cb2bfd0 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
3 locks held by ksoftirqd/1/21:
1 lock held by khungtaskd/27:
 #0: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 #0: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
 #0: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6513
1 lock held by dhcpcd/3932:
 #0: ffffffff8dd401e8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
 #0: ffffffff8dd401e8 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x740/0xed0 net/core/rtnetlink.c:6150
2 locks held by getty/4024:
 #0: ffff88807f710098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
 #1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x41b/0x1380 drivers/tty/n_tty.c:2198
4 locks held by kworker/u4:18/4621:
 #0: ffff888017616938 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc9000571fd00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffffffff8dd33550 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x132/0xb80 net/core/net_namespace.c:594
 #3: ffffffff8dd401e8 (rtnl_mutex){+.+.}-{3:3}, at: wg_destruct+0x21/0x300 drivers/net/wireguard/device.c:246
3 locks held by kworker/0:7/12529:
 #0: ffff88802faa8538 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc9000dcb7d00 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffffffff8dd401e8 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_verify_work+0x15/0x30 net/ipv6/addrconf.c:4673
1 lock held by syz.5.2754/14483:
2 locks held by syz.8.2850/15038:
 #0: ffffffff8d27a8e8 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2045 [inline]
 #0: ffffffff8d27a8e8 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x200/0xd00 drivers/tty/tty_io.c:2128
 #1: ffff88803c7871c0 (&tty->legacy_mutex){+.+.}-{3:3}, at: tty_init_dev+0x70/0x4c0 drivers/tty/tty_io.c:1414
1 lock held by syz.7.2851/15043:
 #0: ffffffff8d27a8e8 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2045 [inline]
 #0: ffffffff8d27a8e8 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x200/0xd00 drivers/tty/tty_io.c:2128
3 locks held by kworker/u4:3/15090:
 #0: ffff888017479138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc90005957d00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffffffff8dd401e8 (rtnl_mutex){+.+.}-{3:3}, at: linkwatch_event+0xa/0x50 net/core/link_watch.c:263
2 locks held by kworker/u4:8/15117:
1 lock held by syz.9.2856/15128:
 #0: ffffffff8d27a8e8 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2045 [inline]
 #0: ffffffff8d27a8e8 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x200/0xd00 drivers/tty/tty_io.c:2128
1 lock held by syz.2.2859/15319:
 #0: ffffffff8d27a8e8 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2045 [inline]
 #0: ffffffff8d27a8e8 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x200/0xd00 drivers/tty/tty_io.c:2128
4 locks held by syz-executor/15411:
 #0: ffff88807ed44460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x256/0x960 fs/read_write.c:580
 #1: ffff8880ae446488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:325
 #2: ffff888144ba7bd0 (kn->active#54){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:326
 #3: ffffffff8d64c548 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: new_device_store+0x129/0x670 drivers/net/netdevsim/bus.c:160
7 locks held by syz-executor/15413:
 #0: ffff88807ed44460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x256/0x960 fs/read_write.c:580
 #1: ffff8880a1da3088 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:325
 #2: ffff888144ba7cb8 (kn->active#53){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:326
 #3: ffffffff8d64c548 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xce/0x360 drivers/net/netdevsim/bus.c:209
 #4: ffff88805623c0e8 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:837 [inline]
 #4: ffff88805623c0e8 (&dev->mutex){....}-{3:3}, at: __device_driver_lock drivers/base/dd.c:1080 [inline]
 #4: ffff88805623c0e8 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal+0xb2/0x850 drivers/base/dd.c:1283
 #5: ffff88805623d2f8 (&devlink->lock_key#4){+.+.}-{3:3}, at: nsim_drv_remove+0x54/0x160 drivers/net/netdevsim/dev.c:1677
 #6: ffffffff8dd401e8 (rtnl_mutex){+.+.}-{3:3}, at: nsim_destroy+0x3b/0x150 drivers/net/netdevsim/netdev.c:381
1 lock held by syz.5.2869/15444:
1 lock held by syz.1.2871/15511:
 #0: ffffffff8d27a8e8 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2045 [inline]
 #0: ffffffff8d27a8e8 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x200/0xd00 drivers/tty/tty_io.c:2128
4 locks held by syz-executor/15553:
 #0: ffff88807ed44460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x256/0x960 fs/read_write.c:580
 #1: ffff8880b2700c88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:325
 #2: ffff888144ba7cb8 (kn->active#53){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:326
 #3: ffffffff8d64c548 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xce/0x360 drivers/net/netdevsim/bus.c:209
1 lock held by syz.8.2873/15560:
 #0: ffffffff8d27a8e8 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2045 [inline]
 #0: ffffffff8d27a8e8 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x200/0xd00 drivers/tty/tty_io.c:2128
1 lock held by syz-executor/15603:
 #0: ffffffff8dd401e8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
 #0: ffffffff8dd401e8 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x740/0xed0 net/core/rtnetlink.c:6150
1 lock held by syz-executor/15657:
 #0: ffffffff8dd401e8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
 #0: ffffffff8dd401e8 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x740/0xed0 net/core/rtnetlink.c:6150
1 lock held by syz-executor/15664:
 #0: ffffffff8dd401e8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
 #0: ffffffff8dd401e8 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x740/0xed0 net/core/rtnetlink.c:6150
1 lock held by syz-executor/15667:
 #0: ffffffff8dd401e8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
 #0: ffffffff8dd401e8 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x740/0xed0 net/core/rtnetlink.c:6150

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

NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted 6.1.147-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3f4/0x470 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x1d4/0x450 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:220 [inline]
 watchdog+0xeee/0xf30 kernel/hung_task.c:377
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 14509 Comm: kworker/1:4 Not tainted 6.1.147-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: wg-crypt-wg2 wg_packet_decrypt_worker
RIP: 0010:__sanitizer_cov_trace_switch+0x0/0xe0 kernel/kcov.c:329
Code: 28 4d 39 ca 77 1e 49 ff c0 4c 89 02 48 c7 44 0a 08 07 00 00 00 48 89 7c 0a 10 48 89 74 0a 18 48 89 44 0a 20 c3 0f 1f 44 00 00 <48> 8b 4e 08 48 83 c1 f8 48 c1 c1 3d 48 83 f9 07 0f 87 c1 00 00 00
RSP: 0018:ffffc900001dfd88 EFLAGS: 00000246
RAX: 0000000000000001 RBX: ffff8880269ba310 RCX: ffff8880272d9dc0
RDX: 0000000000000100 RSI: ffffffff8dda5d00 RDI: 0000000000000001
RBP: 0000000000000001 R08: dffffc0000000000 R09: fffffbfff215ba49
R10: fffffbfff215ba49 R11: 1ffffffff215ba48 R12: 0000000000000000
R13: ffff8880269ba308 R14: 0000000000000001 R15: ffffc900001dfe40
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff3600d277b CR3: 0000000027dc8000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 nf_hook_slow+0xce/0x200 net/netfilter/core.c:615
 nf_hook+0x211/0x370 include/linux/netfilter.h:257
 NF_HOOK_COND include/linux/netfilter.h:290 [inline]
 ip6_output+0x26e/0x3b0 net/ipv6/ip6_output.c:237
 synproxy_send_tcp_ipv6+0x4d5/0x6b0 net/netfilter/nf_synproxy_core.c:851
 synproxy_send_client_synack_ipv6+0x7e4/0xc50 net/netfilter/nf_synproxy_core.c:897
 nft_synproxy_eval_v6+0x36b/0x560 net/netfilter/nft_synproxy.c:90
 nft_synproxy_do_eval+0x3d3/0x570 net/netfilter/nft_synproxy.c:145
 expr_call_ops_eval net/netfilter/nf_tables_core.c:214 [inline]
 nft_do_chain+0x408/0x1600 net/netfilter/nf_tables_core.c:264
 nft_do_chain_inet+0x22b/0x300 net/netfilter/nft_chain_filter.c:161
 nf_hook_entry_hookfn include/linux/netfilter.h:142 [inline]
 nf_hook_slow+0xb9/0x200 net/netfilter/core.c:614
 nf_hook include/linux/netfilter.h:257 [inline]
 NF_HOOK+0x200/0x390 include/linux/netfilter.h:300
 NF_HOOK+0x2ff/0x390 include/linux/netfilter.h:302
 __netif_receive_skb_one_core net/core/dev.c:5569 [inline]
 __netif_receive_skb+0xcc/0x290 net/core/dev.c:5683
 process_backlog+0x37c/0x6e0 net/core/dev.c:6011
 __napi_poll+0xc0/0x460 net/core/dev.c:6578
 napi_poll net/core/dev.c:6645 [inline]
 net_rx_action+0x5b1/0xad0 net/core/dev.c:6759
 handle_softirqs+0x2a1/0x920 kernel/softirq.c:596
 do_softirq+0x13b/0x200 kernel/softirq.c:497
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x174/0x1b0 kernel/softirq.c:421
 spin_unlock_bh include/linux/spinlock.h:396 [inline]
 ptr_ring_consume_bh include/linux/ptr_ring.h:367 [inline]
 wg_packet_decrypt_worker+0x2b5/0xda0 drivers/net/wireguard/receive.c:499
 process_one_work+0x898/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1250 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/27 03:50 linux-6.1.y 3594f306da12 fb8f743d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: task hung in do_fb_ioctl
* Struck through repros no longer work on HEAD.