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INFO: task hung in blkdev_get_by_dev (2)

Status: upstream: reported C repro on 2025/07/08 23:59
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+db3344a4206d7ddec894@syzkaller.appspotmail.com
First crash: 104d, last: 4d18h
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2025/09/28 upstream (ToT) 8f9736633f8c C [report] INFO: task hung in bdev_open
▶ ▼ Similar bugs (11)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: task hung in blkdev_get_by_dev origin:lts-only 1 C done 25 344d 631d 3/3 fixed on 2025/01/02 10:34
linux-5.15 INFO: task hung in blkdev_get_by_dev (2) 1 1 772d 772d 0/3 auto-obsoleted due to no activity on 2023/12/18 22:46
upstream INFO: task hung in blkdev_get_by_dev (3) block 1 1 1322d 1322d 0/29 auto-closed as invalid on 2022/05/08 09:47
linux-5.15 INFO: task hung in blkdev_get_by_dev 1 1 904d 904d 0/3 auto-obsoleted due to no activity on 2023/08/23 09:06
linux-5.15 INFO: task hung in blkdev_get_by_dev (4) 1 3 147d 147d 0/3 auto-obsoleted due to no activity on 2025/09/04 06:30
linux-5.15 INFO: task hung in blkdev_get_by_dev (3) 1 17 408d 628d 0/3 auto-obsoleted due to no activity on 2024/12/17 17:06
upstream INFO: task hung in blkdev_get_by_dev fs 1 1 1701d 1701d 0/29 auto-closed as invalid on 2021/05/23 22:12
upstream INFO: task hung in blkdev_get_by_dev (4) block 1 1 1151d 1151d 0/29 auto-obsoleted due to no activity on 2022/11/25 11:03
linux-6.6 INFO: task hung in blkdev_get_by_dev origin:upstream 1 C 24 10d 122d 0/2 upstream: reported C repro on 2025/06/21 06:39
upstream INFO: task hung in blkdev_get_by_dev (2) block 1 1727 1354d 1433d 0/29 closed as dup on 2021/11/21 14:02
upstream INFO: task hung in blkdev_get_by_dev (5) block 1 C error error 32 192d 964d 0/29 upstream: reported C repro on 2023/03/02 18:11

Sample crash report:
INFO: task udevd:3637 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:udevd           state:D stack:24640 pid:3637  ppid:1      flags:0x00004002
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_preempt_disabled+0xf/0x20 kernel/sched/core.c:6696
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0x555/0xaf0 kernel/locking/mutex.c:747
 blkdev_get_by_dev+0x13d/0xa60 block/bdev.c:815
 blkdev_open+0x11e/0x2e0 block/fops.c:500
 do_dentry_open+0x7e9/0x10d0 fs/open.c:882
 do_open fs/namei.c:3626 [inline]
 path_openat+0x25c6/0x2e70 fs/namei.c:3783
 do_filp_open+0x1c1/0x3c0 fs/namei.c:3810
 do_sys_openat2+0x142/0x490 fs/open.c:1318
 do_sys_open fs/open.c:1334 [inline]
 __do_sys_openat fs/open.c:1350 [inline]
 __se_sys_openat fs/open.c:1345 [inline]
 __x64_sys_openat+0x135/0x160 fs/open.c:1345
 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: 0033:0x7f22b64a7407
RSP: 002b:00007ffefd44c190 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f22b6b53880 RCX: 00007f22b64a7407
RDX: 00000000000a0800 RSI: 0000563b0ab14520 RDI: ffffffffffffff9c
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 0000563ae7807100 R14: 0000000000000000 R15: 00007ffefd44c420
 </TASK>
INFO: task syz.0.23:4458 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.23        state:D stack:27808 pid:4458  ppid:4387   flags:0x00004006
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_preempt_disabled+0xf/0x20 kernel/sched/core.c:6696
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0x555/0xaf0 kernel/locking/mutex.c:747
 blkdev_put+0xfe/0x710 block/bdev.c:913
 blkdev_close+0x51/0x80 block/fops.c:514
 __fput+0x22c/0x920 fs/file_table.c:320
 task_work_run+0x1ca/0x250 kernel/task_work.c:203
 get_signal+0x11a6/0x1350 kernel/signal.c:2648
 arch_do_signal_or_restart+0xb0/0x1230 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fdc3c98eec9
RSP: 002b:00007fdc3d766038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: 0000000000000000 RBX: 00007fdc3cbe5fa0 RCX: 00007fdc3c98eec9
RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000003
RBP: 00007fdc3ca11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdc3cbe6038 R14: 00007fdc3cbe5fa0 R15: 00007ffe7fe8bfd8
 </TASK>

Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/12:
 #0: ffffffff8cb2b570 (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: ffffffff8cb2bd90 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
1 lock held by khungtaskd/28:
 #0: ffffffff8cb2abe0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 #0: ffffffff8cb2abe0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
 #0: ffffffff8cb2abe0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6513
5 locks held by kworker/u4:4/73:
1 lock held by udevd/3637:
 #0: ffff88802486f4c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0x13d/0xa60 block/bdev.c:815
2 locks held by getty/4028:
 #0: ffff88823bd2c098 (&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
1 lock held by udevd/4297:
 #0: ffff88802486f4c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0x13d/0xa60 block/bdev.c:815
1 lock held by syz.0.23/4458:
 #0: ffff88802486f4c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_put+0xfe/0x710 block/bdev.c:913
1 lock held by syz.1.183/4829:
 #0: ffff8880248e2198 (&nbd->config_lock){+.+.}-{3:3}, at: nbd_ioctl+0x140/0xeb0 drivers/block/nbd.c:1535
1 lock held by syz.1.183/4830:
 #0: ffff8880248e2198 (&nbd->config_lock){+.+.}-{3:3}, at: nbd_ioctl+0x140/0xeb0 drivers/block/nbd.c:1535
1 lock held by syz.1.183/4831:
 #0: ffff8880248e2198 (&nbd->config_lock){+.+.}-{3:3}, at: nbd_ioctl+0x140/0xeb0 drivers/block/nbd.c:1535

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

NMI backtrace for cpu 1
CPU: 1 PID: 28 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 3626 Comm: klogd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:instrument_atomic_write include/linux/instrumented.h:87 [inline]
RIP: 0010:atomic_long_set include/linux/atomic/atomic-instrumented.h:1279 [inline]
RIP: 0010:desc_read+0x1b3/0x3f0 kernel/printk/printk_ringbuffer.c:534
Code: 4d 85 e4 75 18 e9 86 01 00 00 e8 68 05 1a 00 4c 8b 64 24 20 4d 85 e4 0f 84 73 01 00 00 e8 55 05 1a 00 4c 89 e7 be 08 00 00 00 <e8> 28 28 6a 00 4c 89 e0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df
RSP: 0018:ffffc90003297958 EFLAGS: 00000293
RAX: ffffffff8166c99b RBX: 00000000ffffec5e RCX: ffff88807ca78000
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffc90003297ae0
RBP: ffffffff8ca19410 R08: dffffc0000000000 R09: fffffbfff1943283
R10: fffffbfff1943283 R11: 1ffffffff1943282 R12: ffffc90003297ae0
R13: 0000000000000002 R14: 00000000ffffec5e R15: 80000000ffffec5e
FS:  00007f75cdf12c80(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fcb5c4a9f98 CR3: 000000007e5d0000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1763 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1831 [inline]
 _prb_read_valid+0x5ff/0xa10 kernel/printk/printk_ringbuffer.c:1891
 prb_read_valid+0x39/0x60 kernel/printk/printk_ringbuffer.c:1940
 syslog_print+0x2be/0x590 kernel/printk/printk.c:1543
 do_syslog+0x7bd/0x8b0 kernel/printk/printk.c:1679
 __do_sys_syslog kernel/printk/printk.c:1771 [inline]
 __se_sys_syslog kernel/printk/printk.c:1769 [inline]
 __x64_sys_syslog+0x78/0x90 kernel/printk/printk.c:1769
 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: 0033:0x7f75ce0dca37
Code: 73 01 c3 48 8b 0d c1 f3 0c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 67 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 91 f3 0c 00 f7 d8 64 89 01 48
RSP: 002b:00007ffc10593368 EFLAGS: 00000206 ORIG_RAX: 0000000000000067
RAX: ffffffffffffffda RBX: 00007f75ce27c490 RCX: 00007f75ce0dca37
RDX: 00000000000003ff RSI: 00007f75ce27c490 RDI: 0000000000000002
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000004000 R11: 0000000000000206 R12: 00007f75ce27c490
R13: 00007f75ce259dfe R14: 00007f75ce27c4c2 R15: 00007f75ce27c4c2
 </TASK>

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/28 16:00 linux-6.1.y 7b34dc04e4ff 001c9061 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: task hung in blkdev_get_by_dev
2025/10/17 03:12 linux-6.1.y c2fda4b3f577 19568248 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: task hung in blkdev_get_by_dev
2025/09/28 13:02 linux-6.1.y 7b34dc04e4ff 001c9061 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: task hung in blkdev_get_by_dev
2025/09/14 20:09 linux-6.1.y 3db754f56897 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: task hung in blkdev_get_by_dev
2025/08/28 18:02 linux-6.1.y f89b6e15694c e12e5ba4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: task hung in blkdev_get_by_dev
2025/08/19 15:34 linux-6.1.y 0bc96de781b4 254a27c1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: task hung in blkdev_get_by_dev
2025/07/08 23:58 linux-6.1.y 04d1ccaa9c28 4d9fdfa4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: task hung in blkdev_get_by_dev
* Struck through repros no longer work on HEAD.