syzbot


INFO: task hung in ext4_readdir (3)

Status: auto-obsoleted due to no activity on 2026/06/20 22:51
Subsystems: ext4
Labels: prio:high
[Documentation on labels]
First crash: 127d, last: 90d
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
88735655-78f8-467f-bd2c-e2453db37e95 assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ✅ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ INFO: task hung in ext4_readdir (3) 2026/05/25 20:59 2026/05/25 20:59 2026/05/25 21:58 c69befb30ac10e158cc9d1557b508ee3f0eca1de

			
		
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in ext4_readdir ext4 1 2 956d 959d 0/29 auto-obsoleted due to no activity on 2024/02/05 13:15
upstream INFO: task hung in ext4_readdir (2) ext4 1 3 750d 750d 0/29 auto-obsoleted due to no activity on 2024/08/30 05:09

Sample crash report:
INFO: task syz.4.210:7181 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.210       state:D stack:26688 pid:7181  tgid:7170  ppid:5807   task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5298 [inline]
 __schedule+0x1553/0x5240 kernel/sched/core.c:6911
 __schedule_loop kernel/sched/core.c:6993 [inline]
 rt_mutex_schedule+0x76/0xf0 kernel/sched/core.c:7289
 rt_mutex_slowlock_block kernel/locking/rtmutex.c:1647 [inline]
 __rt_mutex_slowlock kernel/locking/rtmutex.c:1721 [inline]
 __rt_mutex_slowlock_locked+0x1f8f/0x25c0 kernel/locking/rtmutex.c:1760
 __rwbase_read_lock+0xc3/0x180 kernel/locking/rwbase_rt.c:114
 rwbase_read_lock kernel/locking/rwbase_rt.c:147 [inline]
 __down_read kernel/locking/rwsem.c:1466 [inline]
 down_read+0x132/0x200 kernel/locking/rwsem.c:1539
 inode_lock_shared include/linux/fs.h:1043 [inline]
 dir_relax_shared include/linux/fs.h:3602 [inline]
 ext4_readdir+0x1ebc/0x41b0 fs/ext4/dir.c:315
 iterate_dir+0x3a5/0x580 fs/readdir.c:108
 __do_sys_getdents64 fs/readdir.c:412 [inline]
 __se_sys_getdents64+0xf1/0x280 fs/readdir.c:397
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd4bbdcc799
RSP: 002b:00007fd4b9fdc028 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007fd4bc046180 RCX: 00007fd4bbdcc799
RDX: 0000000000000ffd RSI: 0000200000000f80 RDI: 0000000000000007
RBP: 00007fd4bbe62c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd4bc046218 R14: 00007fd4bc046180 R15: 00007ffdbe2f8768
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/37:
 #0: ffffffff8ddcba40 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 #0: ffffffff8ddcba40 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
 #0: ffffffff8ddcba40 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
3 locks held by kworker/1:1/43:
3 locks held by kworker/1:2/808:
 #0: ffff888019c07938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3251 [inline]
 #0: ffff888019c07938 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0xa52/0x18c0 kernel/workqueue.c:3359
 #1: ffffc9000445fc40 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3252 [inline]
 #1: ffffc9000445fc40 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_scheduled_works+0xa8d/0x18c0 kernel/workqueue.c:3359
 #2: ffff88803f331260 (&data->fib_lock){+.+.}-{4:4}, at: nsim_fib_event_work+0x222/0x3e0 drivers/net/netdevsim/fib.c:1490
6 locks held by kworker/u8:7/1083:
 #0: ffff888028338138 ((wq_completion)loop3){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3251 [inline]
 #0: ffff888028338138 ((wq_completion)loop3){+.+.}-{0:0}, at: process_scheduled_works+0xa52/0x18c0 kernel/workqueue.c:3359
 #1: ffffc90005097c40 ((work_completion)(&worker->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3252 [inline]
 #1: ffffc90005097c40 ((work_completion)(&worker->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa8d/0x18c0 kernel/workqueue.c:3359
 #2: ffff8880258f3160 (&lo->lo_work_lock){+.+.}-{3:3}, at: spin_lock_irq include/linux/spinlock_rt.h:96 [inline]
 #2: ffff8880258f3160 (&lo->lo_work_lock){+.+.}-{3:3}, at: loop_process_work+0xb52/0x11b0 drivers/block/loop.c:1963
 #3: ffffffff8ddcba40 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 #3: ffffffff8ddcba40 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
 #3: ffffffff8ddcba40 (rcu_read_lock){....}-{1:3}, at: __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline]
 #3: ffffffff8ddcba40 (rcu_read_lock){....}-{1:3}, at: rt_spin_lock+0x1e0/0x400 kernel/locking/spinlock_rt.c:57
 #4: ffffffff8e555a00 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: debug_objects_fill_pool+0x6f/0xd0 lib/debugobjects.c:741
 #5: ffff88813fe37758 (&n->list_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
 #5: ffff88813fe37758 (&n->list_lock){+.+.}-{3:3}, at: get_from_partial_node+0x54/0x480 mm/slub.c:3810
5 locks held by kworker/u8:12/2223:
3 locks held by udevd/5166:
 #0: ffff88801aef5258 (&kernfs_locks->open_file_mutex[count]){+.+.}-{4:4}, at: kernfs_open_file_mutex_lock fs/kernfs/file.c:56 [inline]
 #0: ffff88801aef5258 (&kernfs_locks->open_file_mutex[count]){+.+.}-{4:4}, at: kernfs_unlink_open_file+0x6d/0x4d0 fs/kernfs/file.c:583
 #1: ffffffff8e555a00 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: debug_objects_fill_pool+0x6f/0xd0 lib/debugobjects.c:741
 #2: ffff88813fe37758 (&n->list_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
 #2: ffff88813fe37758 (&n->list_lock){+.+.}-{3:3}, at: get_from_partial_node+0x54/0x480 mm/slub.c:3810
2 locks held by getty/5553:
 #0: ffff888036cf50a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90003e762e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x462/0x13c0 drivers/tty/n_tty.c:2211
2 locks held by syz-executor/5795:
 #0: ffffffff8e555a00 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: debug_objects_fill_pool+0x6f/0xd0 lib/debugobjects.c:741
 #1: ffff88813fe37758 (&n->list_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
 #1: ffff88813fe37758 (&n->list_lock){+.+.}-{3:3}, at: get_from_partial_node+0x54/0x480 mm/slub.c:3810
4 locks held by udevd/5804:
2 locks held by syz-executor/5808:
 #0: ffffffff8e555a00 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: debug_objects_fill_pool+0x6f/0xd0 lib/debugobjects.c:741
 #1: ffff88813fe37758 (&n->list_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
 #1: ffff88813fe37758 (&n->list_lock){+.+.}-{3:3}, at: get_from_partial_node+0x54/0x480 mm/slub.c:3810
3 locks held by kworker/1:5/5911:
 #0: ffff888019c07938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3251 [inline]
 #0: ffff888019c07938 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0xa52/0x18c0 kernel/workqueue.c:3359
 #1: ffffc90004e97c40 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3252 [inline]
 #1: ffffc90004e97c40 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_scheduled_works+0xa8d/0x18c0 kernel/workqueue.c:3359
 #2: ffff8880608a2260 (&data->fib_lock){+.+.}-{4:4}, at: nsim_fib_event_work+0x222/0x3e0 drivers/net/netdevsim/fib.c:1490
4 locks held by udevd/5945:
 #0: ffff888036bce258 (&group->inotify_data.idr_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
 #0: ffff888036bce258 (&group->inotify_data.idr_lock){+.+.}-{3:3}, at: inotify_remove_from_idr+0x34/0x510 fs/notify/inotify/inotify_user.c:460
 #1: ffffffff8ddcba40 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 #1: ffffffff8ddcba40 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
 #1: ffffffff8ddcba40 (rcu_read_lock){....}-{1:3}, at: __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline]
 #1: ffffffff8ddcba40 (rcu_read_lock){....}-{1:3}, at: rt_spin_lock+0x1e0/0x400 kernel/locking/spinlock_rt.c:57
 #2: ffffffff8e555a00 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: debug_objects_fill_pool+0x6f/0xd0 lib/debugobjects.c:741
 #3: ffff88813fe37758 (&n->list_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
 #3: ffff88813fe37758 (&n->list_lock){+.+.}-{3:3}, at: get_from_partial_node+0x54/0x480 mm/slub.c:3810
2 locks held by syz-executor/7132:
 #0: ffffffff8e555a00 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: debug_objects_fill_pool+0x6f/0xd0 lib/debugobjects.c:741
 #1: ffff88813fe37758 (&n->list_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
 #1: ffff88813fe37758 (&n->list_lock){+.+.}-{3:3}, at: get_from_partial_node+0x54/0x480 mm/slub.c:3810
7 locks held by syz.4.210/7172:
2 locks held by syz.4.210/7181:
 #0: ffff88803b90bb28 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1261
 #1: ffff8880401257d0 (&type->i_mutex_dir_key#3){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1043 [inline]
 #1: ffff8880401257d0 (&type->i_mutex_dir_key#3){++++}-{4:4}, at: dir_relax_shared include/linux/fs.h:3602 [inline]
 #1: ffff8880401257d0 (&type->i_mutex_dir_key#3){++++}-{4:4}, at: ext4_readdir+0x1ebc/0x41b0 fs/ext4/dir.c:315
1 lock held by syz-executor/7216:
 #0: ffff8880653400d0 (&type->s_umount_key#59){++++}-{4:4}, at: __super_lock fs/super.c:58 [inline]
 #0: ffff8880653400d0 (&type->s_umount_key#59){++++}-{4:4}, at: __super_lock_excl fs/super.c:73 [inline]
 #0: ffff8880653400d0 (&type->s_umount_key#59){++++}-{4:4}, at: deactivate_super+0xa9/0xe0 fs/super.c:508
2 locks held by syz-executor/8576:
1 lock held by syz-executor/8582:
2 locks held by syz.6.492/8759:
3 locks held by syz.1.493/8764:
6 locks held by syz.3.495/8778:
 #0: ffff88802b5aa480 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:493
 #1: ffff88804035f778 (&type->i_mutex_dir_key#8){++++}-{4:4}, at: inode_lock include/linux/fs.h:1028 [inline]
 #1: ffff88804035f778 (&type->i_mutex_dir_key#8){++++}-{4:4}, at: open_last_lookups fs/namei.c:4580 [inline]
 #1: ffff88804035f778 (&type->i_mutex_dir_key#8){++++}-{4:4}, at: path_openat+0xb5e/0x38a0 fs/namei.c:4827
 #2: ffff88804035f4b8 (&ni->ni_lock/6){+.+.}-{4:4}, at: ni_lock_dir fs/ntfs3/ntfs_fs.h:1222 [inline]
 #2: ffff88804035f4b8 (&ni->ni_lock/6){+.+.}-{4:4}, at: ntfs_lookup+0xf3/0x1d0 fs/ntfs3/namei.c:84
 #3: ffff88804035f588 (&indx->run_lock){++++}-{4:4}, at: indx_read_ra+0x2d7/0xc00 fs/ntfs3/index.c:1065
 #4: ffffffff8ddcba40 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 #4: ffffffff8ddcba40 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
 #4: ffffffff8ddcba40 (rcu_read_lock){....}-{1:3}, at: blk_mq_dispatch_queue_requests+0x552/0x800 block/blk-mq.c:2908
 #5: ffff8880258f3160 (&lo->lo_work_lock){+.+.}-{3:3}, at: spin_lock_irq include/linux/spinlock_rt.h:96 [inline]
 #5: ffff8880258f3160 (&lo->lo_work_lock){+.+.}-{3:3}, at: loop_queue_work drivers/block/loop.c:803 [inline]
 #5: ffff8880258f3160 (&lo->lo_work_lock){+.+.}-{3:3}, at: loop_queue_rq+0x23c/0xb00 drivers/block/loop.c:1889
2 locks held by dhcpcd-run-hook/8794:

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 37 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:161 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x135/0x170 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:346 [inline]
 watchdog+0xfd9/0x1030 kernel/hung_task.c:515
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
 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: 8759 Comm: syz.6.492 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:__lock_is_held kernel/locking/lockdep.c:5601 [inline]
RIP: 0010:lock_is_held_type+0x89/0x150 kernel/locking/lockdep.c:5940
Code: 2b 07 41 83 bd b0 0b 00 00 00 7e 48 4c 89 eb 48 81 c3 b8 0b 00 00 45 31 ff 49 83 ff 31 73 24 48 89 df 4c 89 f6 e8 f7 01 00 00 <85> c0 75 2a 49 ff c7 49 63 85 b0 0b 00 00 48 83 c3 28 49 39 c7 7c
RSP: 0018:ffffc900079a70d0 EFLAGS: 00000046
RAX: 0000000000000000 RBX: ffff88802ff20c08 RCX: 0000000080000003
RDX: 0000000000000008 RSI: ffff88801ffcc7f0 RDI: ffff88802ff20c08
RBP: 00000000ffffffff R08: ffffffff8f6a5cb7 R09: 1ffffffff1ed4b96
R10: dffffc0000000000 R11: ffffffff819756e0 R12: 0000000000000046
R13: ffff88802ff20000 R14: ffff88801ffcc7f0 R15: 0000000000000002
FS:  00007f2632d166c0(0000) GS:ffff888126339000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2f318ff8 CR3: 000000003cdc2000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 lock_is_held include/linux/lockdep.h:249 [inline]
 select_task_rq_fair+0xac/0x4360 kernel/sched/fair.c:8597
 select_task_rq kernel/sched/core.c:3521 [inline]
 try_to_wake_up+0x4db/0x1380 kernel/sched/core.c:4230
 kick_pool+0x47d/0x640 kernel/workqueue.c:1298
 __queue_work+0xcd3/0xff0 kernel/workqueue.c:2355
 queue_work_on+0x106/0x1d0 kernel/workqueue.c:2405
 queue_work include/linux/workqueue.h:669 [inline]
 xlog_cil_push_now fs/xfs/xfs_log_cil.c:1749 [inline]
 xlog_cil_force_seq+0x363/0x8c0 fs/xfs/xfs_log_cil.c:1927
 xlog_cil_force fs/xfs/xfs_log_priv.h:585 [inline]
 xfs_log_force+0x1ad/0x950 fs/xfs/xfs_log.c:2802
 xfs_qm_dqflush+0x987/0x11c0 fs/xfs/xfs_dquot.c:1435
 xfs_qm_flush_one+0x13c/0x200 fs/xfs/xfs_qm.c:1442
 xfs_qm_dquot_walk+0x28a/0x5d0 fs/xfs/xfs_qm.c:90
 xfs_qm_quotacheck+0x3ba/0x6f0 fs/xfs/xfs_qm.c:1525
 xfs_qm_mount_quotas+0x26a/0x670 fs/xfs/xfs_qm.c:1646
 xfs_mountfs+0x1b16/0x22e0 fs/xfs/xfs_mount.c:1189
 xfs_fs_fill_super+0x11b5/0x1600 fs/xfs/xfs_super.c:1938
 get_tree_bdev_flags+0x431/0x4f0 fs/super.c:1694
 vfs_get_tree+0x92/0x2a0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3763 [inline]
 do_new_mount+0x341/0xd30 fs/namespace.c:3839
 do_mount fs/namespace.c:4172 [inline]
 __do_sys_mount fs/namespace.c:4361 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4338
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2634abda0a
Code: 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2632d15e58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f2632d15ee0 RCX: 00007f2634abda0a
RDX: 0000200000009740 RSI: 0000200000009780 RDI: 00007f2632d15ea0
RBP: 0000200000009740 R08: 00007f2632d15ee0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000200000009780
R13: 00007f2632d15ea0 R14: 0000000000009764 R15: 0000200000000000
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/22 22:49 upstream 8d8bd2a5aa98 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs INFO: task hung in ext4_readdir
2026/02/15 12:27 upstream c22e26bd0906 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs INFO: task hung in ext4_readdir
2026/02/13 20:32 upstream c22e26bd0906 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs INFO: task hung in ext4_readdir
* Struck through repros no longer work on HEAD.