INFO: task hung in __block_write_begin_int

Status: upstream: reported on 2026/09/17 10:59
Reported-by: syzbot+fc6be79c8bce296e5d65@syzkaller.appspotmail.com
First crash: 11d, last: 11d
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in __block_write_begin_int fs 1 1 3109d 3109d 0/29 closed as invalid on 2018/03/27 11:14
linux-6.6 INFO: task hung in __block_write_begin_int 1 1 10d 10d 0/2 upstream: reported on 2026/09/18 17:26

Sample crash report:
INFO: task syz.2.364:6284 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.364       state:D stack:0     pid:6284  ppid:4334   flags:0x00000009
Call trace:
 __switch_to+0x2f4/0x550 arch/arm64/kernel/process.c:555
 context_switch kernel/sched/core.c:5246 [inline]
 __schedule+0xdb4/0x1a6c kernel/sched/core.c:6563
 schedule+0xc4/0x170 kernel/sched/core.c:6639
 io_schedule+0x84/0x154 kernel/sched/core.c:8799
 bit_wait_io+0x1c/0xac kernel/sched/wait_bit.c:209
 __wait_on_bit kernel/sched/wait_bit.c:49 [inline]
 out_of_line_wait_on_bit+0x168/0x208 kernel/sched/wait_bit.c:64
 wait_on_bit_io include/linux/wait_bit.h:101 [inline]
 __wait_on_buffer fs/buffer.c:122 [inline]
 wait_on_buffer include/linux/buffer_head.h:385 [inline]
 __block_write_begin_int+0x1220/0x13c0 fs/buffer.c:2029
 __block_write_begin fs/buffer.c:2041 [inline]
 block_write_begin+0x98/0x11c fs/buffer.c:2102
 blkdev_write_begin+0x44/0x58 block/fops.c:407
 generic_perform_write+0x240/0x508 mm/filemap.c:3862
 blkdev_write_iter+0x3c8/0x5c4 block/fops.c:601
 call_write_iter include/linux/fs.h:2271 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x3c8/0x7c8 fs/read_write.c:584
 ksys_pwrite64 fs/read_write.c:699 [inline]
 __do_sys_pwrite64 fs/read_write.c:709 [inline]
 __se_sys_pwrite64 fs/read_write.c:706 [inline]
 __arm64_sys_pwrite64+0x178/0x210 fs/read_write.c:706
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
INFO: task syz.0.401:6520 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.401       state:D stack:0     pid:6520  ppid:4336   flags:0x00000009
Call trace:
 __switch_to+0x2f4/0x550 arch/arm64/kernel/process.c:555
 context_switch kernel/sched/core.c:5246 [inline]
 __schedule+0xdb4/0x1a6c kernel/sched/core.c:6563
 schedule+0xc4/0x170 kernel/sched/core.c:6639
 io_schedule+0x84/0x154 kernel/sched/core.c:8799
 bit_wait_io+0x1c/0xac kernel/sched/wait_bit.c:209
 __wait_on_bit kernel/sched/wait_bit.c:49 [inline]
 out_of_line_wait_on_bit+0x168/0x208 kernel/sched/wait_bit.c:64
 wait_on_bit_io include/linux/wait_bit.h:101 [inline]
 __wait_on_buffer fs/buffer.c:122 [inline]
 wait_on_buffer include/linux/buffer_head.h:385 [inline]
 __block_write_begin_int+0x1220/0x13c0 fs/buffer.c:2029
 __block_write_begin fs/buffer.c:2041 [inline]
 block_write_begin+0x98/0x11c fs/buffer.c:2102
 blkdev_write_begin+0x44/0x58 block/fops.c:407
 generic_perform_write+0x240/0x508 mm/filemap.c:3862
 blkdev_write_iter+0x3c8/0x5c4 block/fops.c:601
 call_write_iter include/linux/fs.h:2271 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x3c8/0x7c8 fs/read_write.c:584
 ksys_pwrite64 fs/read_write.c:699 [inline]
 __do_sys_pwrite64 fs/read_write.c:709 [inline]
 __se_sys_pwrite64 fs/read_write.c:706 [inline]
 __arm64_sys_pwrite64+0x178/0x210 fs/read_write.c:706
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/12:
 #0: ffff800015597db0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x40/0xc48 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
 #0: ffff8000155985d0
 (rcu_tasks_trace.tasks_gp_mutex
){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x40/0xc48 kernel/rcu/tasks.h:517
3 locks held by kworker/0:1/14:
 #0: ffff0000c0020938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x69c/0x13bc kernel/workqueue.c:-1
 #1: ffff80001cbc7c40 ((work_completion)(&wdata->init_worker)){+.+.}-{0:0}, at: process_one_work+0x6e8/0x13bc kernel/workqueue.c:2267
 #2: ffff0001166803a0 (&wdata->state.sync){+.+.}-{3:3}
, at: wiimote_cmd_acquire_noint drivers/hid/hid-wiimote.h:327 [inline]
, at: wiimote_init_hotplug drivers/hid/hid-wiimote-core.c:1103 [inline]
, at: wiimote_init_worker+0xb34/0x2434 drivers/hid/hid-wiimote-core.c:1215
1 lock held by khungtaskd/28:
 #0: ffff800015597440
 (
rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0xc/0x44 include/linux/rcupdate.h:349
5 locks held by udevd/3939:
 #0: ffff0001004582f0 (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0xb4/0xc24 fs/seq_file.c:182
 #1: ffff0000f1970c88 (
&of->mutex
){+.+.}-{3:3}
, at: kernfs_seq_start+0x58/0x3b8 fs/kernfs/file.c:172
 #2: ffff000105946e88 (
kn->active#4
){++++}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
){++++}-{0:0}, at: kernfs_seq_start+0xa4/0x3b8 fs/kernfs/file.c:173
 #3: ffff0000d9c41120 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:885 [inline]
 #3: ffff0000d9c41120 (&dev->mutex){....}-{3:3}, at: uevent_show+0x168/0x328 drivers/base/core.c:2669
 #4: ffff000114d803a0 (&wdata->state.sync){+.+.}-{3:3}, at: wiimote_cmd_acquire drivers/hid/hid-wiimote.h:322 [inline]
 #4: ffff000114d803a0 (&wdata->state.sync){+.+.}-{3:3}, at: wiimod_battery_get_property+0x78/0x230 drivers/hid/hid-wiimote-modules.c:214
2 locks held by getty/4080:
 #0: ffff0000d6e3f098 (&tty->ldisc_sem){++++}-{0:0}, at: ldsem_down_read+0x3c/0x4c drivers/tty/tty_ldsem.c:340
 #1: ffff800020a7e2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x2e8/0xfa8 drivers/tty/n_tty.c:2198
1 lock held by syz.2.364/6284:
 #0: ffff0000c521a840 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: inode_lock_shared include/linux/fs.h:774 [inline]
 #0: ffff0000c521a840 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: blkdev_write_iter+0x3bc/0x5c4 block/fops.c:600
1 lock held by syz.0.401/6520:
 #0: ffff0000c521a840 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: inode_lock_shared include/linux/fs.h:774 [inline]
 #0: ffff0000c521a840 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: blkdev_write_iter+0x3bc/0x5c4 block/fops.c:600
3 locks held by udevd/9817:
 #0: ffff0000dc7b3110 (&evdev->mutex){+.+.}-{3:3}, at: evdev_open_device drivers/input/evdev.c:398 [inline]
 #0: ffff0000dc7b3110 (&evdev->mutex){+.+.}-{3:3}, at: evdev_open+0x228/0x474 drivers/input/evdev.c:492
 #1: ffff0000dc7b12c0 (&dev->mutex#2){+.+.}-{3:3}, at: input_open_device+0x54/0x288 drivers/input/input.c:630
 #2: ffff000114d803a0 (&wdata->state.sync){+.+.}-{3:3}, at: wiimote_cmd_acquire drivers/hid/hid-wiimote.h:322 [inline]
 #2: ffff000114d803a0 (&wdata->state.sync){+.+.}-{3:3}, at: wiimod_ir_change+0x134/0x76c drivers/hid/hid-wiimote-modules.c:636
2 locks held by kworker/0:8/10279:
 #0: ffff0000c4410938 ((wq_completion)md_misc){+.+.}-{0:0}, at: process_one_work+0x69c/0x13bc kernel/workqueue.c:-1
 #1: ffff800023947c40 ((work_completion)(&mddev->del_work)){+.+.}-{0:0}, at: process_one_work+0x6e8/0x13bc kernel/workqueue.c:2267
3 locks held by syz.5.961/18369:
 #0: 
ffff0000fe770fe8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x118/0x17c fs/file.c:1038
 #1: 
ffff0000df472460 (sb_writers#13){.+.+}-{0:0}, at: vfs_write+0x254/0x7c8 fs/read_write.c:580
 #2: ffff8000158242c8 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xbc/0x9f0 fs/nfsd/nfsctl.c:846
3 locks held by syz.5.961/18384:
 #0: ffff0000fe6ab268 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x118/0x17c fs/file.c:1038
 #1: 
ffff0000df472460
 (sb_writers
#13){.+.+}-{0:0}, at: vfs_write+0x254/0x7c8 fs/read_write.c:580
 #2: ffff8000158242c8 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_svc+0x74/0x948 fs/nfsd/nfssvc.c:783
3 locks held by syz.1.960/18370:
 #0: ffff0000fe240fe8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x118/0x17c fs/file.c:1038
 #1: ffff0000df198460 (sb_writers#13){.+.+}-{0:0}, at: vfs_write+0x254/0x7c8 fs/read_write.c:580
 #2: ffff8000158242c8 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_svc+0x74/0x948 fs/nfsd/nfssvc.c:783
3 locks held by syz.3.1065/25722:
 #0: ffff0000fa95d768 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x118/0x17c fs/file.c:1038
 #1: ffff0000dc354460 (sb_writers#13){.+.+}-{0:0}, at: vfs_write+0x254/0x7c8 fs/read_write.c:580
 #2: ffff8000158242c8 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xbc/0x9f0 fs/nfsd/nfsctl.c:846
3 locks held by syz.3.1065/25737:
 #0: 
ffff0000ce053c68 (&f->f_pos_lock
){+.+.}-{3:3}
, at: __fdget_pos+0x118/0x17c fs/file.c:1038
 #1: 
ffff0000dc354460
 (
sb_writers#13){.+.+}-{0:0}, at: vfs_write+0x254/0x7c8 fs/read_write.c:580
 #2: ffff8000158242c8 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_svc+0x74/0x948 fs/nfsd/nfssvc.c:783
3 locks held by syz.7.1073/26945:
 #0: ffff0000cb651768 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x118/0x17c fs/file.c:1038
 #1: ffff0000d9970460 (sb_writers#13){.+.+}-{0:0}, at: vfs_write+0x254/0x7c8 fs/read_write.c:580
 #2: ffff8000158242c8 (nfsd_mutex){+.+.}-{3:3}, at: write_versions+0xa4/0xa34 fs/nfsd/nfsctl.c:681
3 locks held by syz.7.1073/26967:
 #0: ffff0000fe8f6368 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x118/0x17c fs/file.c:1038
 #1: ffff0000d9970460 (sb_writers#13){.+.+}-{0:0}, at: vfs_write+0x254/0x7c8 fs/read_write.c:580
 #2: ffff8000158242c8 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xbc/0x9f0 fs/nfsd/nfsctl.c:846
3 locks held by syz.7.1073/26987:
 #0: ffff0000cacd0ae8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x118/0x17c fs/file.c:1038
 #1: ffff0000d9970460 (sb_writers#13){.+.+}-{0:0}, at: vfs_write+0x254/0x7c8 fs/read_write.c:580
 #2: ffff8000158242c8 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_svc+0x74/0x948 fs/nfsd/nfssvc.c:783
3 locks held by syz.8.1196/6765:
 #0: ffff0000d3cd7268 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x118/0x17c fs/file.c:1038
 #1: ffff000100562460 (sb_writers#13){.+.+}-{0:0}, at: vfs_write+0x254/0x7c8 fs/read_write.c:580
 #2: ffff8000158242c8 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xbc/0x9f0 fs/nfsd/nfsctl.c:846
3 locks held by syz.8.1196/6785:
 #0: ffff000106a699e8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x118/0x17c fs/file.c:1038
 #1: ffff000100562460 (sb_writers#13){.+.+}-{0:0}, at: vfs_write+0x254/0x7c8 fs/read_write.c:580
 #2: ffff8000158242c8 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_svc+0x74/0x948 fs/nfsd/nfssvc.c:783
2 locks held by syz.9.1272/13696:
 #0: ffff00010fd6da20 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:885 [inline]
 #0: ffff00010fd6da20 (&dev->mutex){....}-{3:3}, at: __device_driver_lock drivers/base/dd.c:1099 [inline]
 #0: ffff00010fd6da20 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal+0x9c/0x6e4 drivers/base/dd.c:1302
 #1: ffff0000dc7b12c0 (&dev->mutex#2){+.+.}-{3:3}, at: input_disconnect_device drivers/input/input.c:757 [inline]
 #1: ffff0000dc7b12c0 (&dev->mutex#2){+.+.}-{3:3}, at: __input_unregister_device+0x38/0x55c drivers/input/input.c:2291
3 locks held by syz.0.1284/14842:
 #0: ffff0000fa94efe8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x118/0x17c fs/file.c:1038
 #1: ffff0000d1800460 (sb_writers#13){.+.+}-{0:0}, at: vfs_write+0x254/0x7c8 fs/read_write.c:580
 #2: ffff8000158242c8 (nfsd_mutex){+.+.}-{3:3}, at: write_versions+0xa4/0xa34 fs/nfsd/nfsctl.c:681
3 locks held by syz.0.1284/14864:
 #0: ffff0000ffed6868 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x118/0x17c fs/file.c:1038
 #1: ffff0000d1800460 (sb_writers#13){.+.+}-{0:0}, at: vfs_write+0x254/0x7c8 fs/read_write.c:580
 #2: ffff8000158242c8 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xbc/0x9f0 fs/nfsd/nfsctl.c:846
3 locks held by syz.0.1284/14881:
 #0: ffff0000fe6cb4e8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x118/0x17c fs/file.c:1038
 #1: ffff0000d1800460 (sb_writers#13){.+.+}-{0:0}, at: vfs_write+0x254/0x7c8 fs/read_write.c:580
 #2: ffff8000158242c8 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_svc+0x74/0x948 fs/nfsd/nfssvc.c:783
1 lock held by syz.2.1291/14934:
 #0: ffff000100bf1a20 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:885 [inline]
 #0: ffff000100bf1a20 (&dev->mutex){....}-{3:3}, at: __device_driver_lock drivers/base/dd.c:1099 [inline]
 #0: ffff000100bf1a20 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal+0x9c/0x6e4 drivers/base/dd.c:1302

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


Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/17 10:59 linux-6.1.y 1a8763b93150 95928915 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 INFO: task hung in __block_write_begin_int
* Struck through repros no longer work on HEAD.