syzbot


INFO: task hung in kernfs_seq_start

Status: auto-obsoleted due to no activity on 2025/05/21 23:16
Subsystems: kernfs
[Documentation on labels]
First crash: 102d, last: 102d

Sample crash report:
INFO: task syz.3.789:9291 blocked for more than 143 seconds.
      Not tainted 6.14.0-rc3-syzkaller-00096-ge9a8cac0bf89 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.789       state:D stack:27936 pid:9291  tgid:9286  ppid:5836   task_flags:0x400140 flags:0x00000004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5378 [inline]
 __schedule+0xf43/0x5890 kernel/sched/core.c:6765
 __schedule_loop kernel/sched/core.c:6842 [inline]
 schedule+0xe7/0x350 kernel/sched/core.c:6857
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6914
 __mutex_lock_common kernel/locking/mutex.c:662 [inline]
 __mutex_lock+0x6bd/0xb10 kernel/locking/mutex.c:730
 kernfs_seq_start+0x4d/0x240 fs/kernfs/file.c:154
 seq_read_iter+0x2ab/0x12b0 fs/seq_file.c:225
 kernfs_fop_read_iter+0x414/0x580 fs/kernfs/file.c:279
 copy_splice_read+0x61d/0xb80 fs/splice.c:365
 do_splice_read fs/splice.c:985 [inline]
 do_splice_read+0x282/0x370 fs/splice.c:959
 splice_direct_to_actor+0x2a4/0xa40 fs/splice.c:1089
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0x178/0x250 fs/splice.c:1233
 do_sendfile+0xafb/0xe40 fs/read_write.c:1363
 __do_sys_sendfile64 fs/read_write.c:1424 [inline]
 __se_sys_sendfile64 fs/read_write.c:1410 [inline]
 __x64_sys_sendfile64+0x1da/0x220 fs/read_write.c:1410
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f113d78d0a9
RSP: 002b:00007f113e569038 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f113d9a6160 RCX: 00007f113d78d0a9
RDX: 0000000000000000 RSI: 0000000000000007 RDI: 0000000000000007
RBP: 00007f113d80e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000200 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f113d9a6160 R15: 00007ffd2305c948
 </TASK>

Showing all locks held in the system:
1 lock held by kthreadd/2:
3 locks held by kworker/0:0/8:
 #0: ffff88801b081d48 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3211
 #1: ffffc900000d7d18 ((reg_check_chans).work){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3212
 #2: ffffffff8fef8a28 (rtnl_mutex){+.+.}-{4:4}, at: reg_check_chans_work+0x84/0x1130 net/wireless/reg.c:2480
3 locks held by kworker/u8:1/12:
1 lock held by khungtaskd/30:
 #0: ffffffff8e1bcc80 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
 #0: ffffffff8e1bcc80 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffffffff8e1bcc80 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x7f/0x390 kernel/locking/lockdep.c:6746
3 locks held by kworker/u8:3/52:
3 locks held by kworker/u8:4/63:
3 locks held by kworker/0:2/974:
 #0: ffff88801b080d48 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3211
 #1: ffffc90003edfd18 (deferred_process_work){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3212
 #2: ffffffff8fef8a28 (rtnl_mutex){+.+.}-{4:4}, at: switchdev_deferred_process_work+0xe/0x20 net/switchdev/switchdev.c:104
6 locks held by kworker/u8:5/1003:
3 locks held by kworker/u8:6/1099:
 #0: ffff888031366148 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3211
 #1: ffffc9000425fd18 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3212
 #2: ffffffff8fef8a28 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:129 [inline]
 #2: ffffffff8fef8a28 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_verify_work+0x12/0x30 net/ipv6/addrconf.c:4730
3 locks held by kworker/u8:7/1129:
3 locks held by kworker/u8:12/3533:
4 locks held by kworker/u8:13/3565:
 #0: ffff88801bef5948 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3211
 #1: ffffc9000ce37d18 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3212
 #2: ffffffff8fee2d50 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xca/0xbf0 net/core/net_namespace.c:606
 #3: ffffffff8fef8a28 (rtnl_mutex){+.+.}-{4:4}, at: ip6mr_net_exit_batch+0x15/0xa0 net/ipv6/ip6mr.c:1386
1 lock held by syslogd/5195:
2 locks held by dhcpcd/5506:
4 locks held by dhcpcd/5507:
2 locks held by getty/5605:
 #0: ffff888031e290a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc90002fde2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0xfba/0x1480 drivers/tty/n_tty.c:2211
5 locks held by syz-executor/5834:
3 locks held by syz-executor/5835:
2 locks held by syz.3.740/9104:
1 lock held by syz.2.777/9247:
3 locks held by syz.4.788/9299:
5 locks held by syz.3.789/9288:
2 locks held by syz.3.789/9291:
 #0: ffff88806332d790 (&p->lock){+.+.}-{4:4}, at: seq_read_iter+0xd8/0x12b0 fs/seq_file.c:182
 #1: ffff88803582f888 (&of->mutex){+.+.}-{4:4}, at: kernfs_seq_start+0x4d/0x240 fs/kernfs/file.c:154
3 locks held by kworker/u8:9/9302:
3 locks held by kworker/u8:10/9303:
2 locks held by kworker/0:5/9306:
3 locks held by kworker/u8:14/9307:
2 locks held by syz-executor/9310:

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 30 Comm: khungtaskd Not tainted 6.14.0-rc3-syzkaller-00096-ge9a8cac0bf89 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
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:162 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:236 [inline]
 watchdog+0xf62/0x12b0 kernel/hung_task.c:399
 kthread+0x3af/0x750 kernel/kthread.c:464
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 1003 Comm: kworker/u8:5 Not tainted 6.14.0-rc3-syzkaller-00096-ge9a8cac0bf89 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Workqueue: bat_events batadv_tt_purge
RIP: 0010:ipv6_masked_addr_cmp include/net/ipv6.h:600 [inline]
RIP: 0010:ip6_packet_match net/ipv6/netfilter/ip6_tables.c:60 [inline]
RIP: 0010:ip6t_do_table+0x5f3/0x1d40 net/ipv6/netfilter/ip6_tables.c:306
Code: 00 0f 85 c9 13 00 00 49 8d 7f 20 49 23 46 30 48 be 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 32 00 0f 85 94 13 00 00 <49> 8d 7e 18 4d 8b 6f 20 48 b9 00 00 00 00 00 fc ff df 48 89 fa 48
RSP: 0018:ffffc90000006a00 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: dffffc0000000000
RDX: 1ffff1100cc6cc86 RSI: dffffc0000000000 RDI: ffff888066366430
RBP: ffff888032423500 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000005 R12: ffff888061589404
R13: 0000000000000000 R14: ffff888061589380 R15: ffff888066366410
FS:  0000000000000000(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f30ca82aff8 CR3: 0000000034882000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <NMI>
 </NMI>
 <IRQ>
 ip6table_mangle_hook+0xc4/0x770 net/ipv6/netfilter/ip6table_mangle.c:73
 nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline]
 nf_hook_slow+0xbb/0x200 net/netfilter/core.c:626
 nf_hook+0x486/0x810 include/linux/netfilter.h:269
 NF_HOOK include/linux/netfilter.h:312 [inline]
 br_nf_post_routing+0x8c4/0x11b0 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+0x474/0x7d0 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+0x303/0x410 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+0x610/0x820 net/bridge/br_netfilter_hooks.c:719
 br_nf_forward_ip net/bridge/br_netfilter_hooks.c:679 [inline]
 br_nf_forward+0xf11/0x1bd0 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+0x474/0x7d0 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+0x5b/0xa0 net/bridge/br_forward.c:131
 br_flood+0x491/0x5e0 net/bridge/br_forward.c:249
 br_handle_frame_finish+0xea2/0x1c90 net/bridge/br_input.c:220
 br_nf_hook_thresh+0x303/0x410 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+0x3ce/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+0xad7/0x14a0 net/bridge/br_input.c:433
 __netif_receive_skb_core.constprop.0+0xa20/0x4330 net/core/dev.c:5722
 __netif_receive_skb_one_core+0xb1/0x1e0 net/core/dev.c:5826
 __netif_receive_skb+0x1d/0x160 net/core/dev.c:5941
 process_backlog+0x443/0x15f0 net/core/dev.c:6289
 __napi_poll.constprop.0+0xb7/0x550 net/core/dev.c:7106
 napi_poll net/core/dev.c:7175 [inline]
 net_rx_action+0xa94/0x1010 net/core/dev.c:7297
 handle_softirqs+0x213/0x8f0 kernel/softirq.c:561
 do_softirq kernel/softirq.c:462 [inline]
 do_softirq+0xb2/0xf0 kernel/softirq.c:449
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x100/0x120 kernel/softirq.c:389
 spin_unlock_bh include/linux/spinlock.h:396 [inline]
 batadv_tt_global_purge net/batman-adv/translation-table.c:2250 [inline]
 batadv_tt_purge+0x251/0xb90 net/batman-adv/translation-table.c:3510
 process_one_work+0x9c5/0x1ba0 kernel/workqueue.c:3236
 process_scheduled_works kernel/workqueue.c:3317 [inline]
 worker_thread+0x6c8/0xf00 kernel/workqueue.c:3398
 kthread+0x3af/0x750 kernel/kthread.c:464
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/02/20 23:13 upstream e9a8cac0bf89 0808a665 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in kernfs_seq_start
* Struck through repros no longer work on HEAD.