Re: [syzbot] [ext4?] INFO: task jbd2/sda1-NUM:NUM blocked in I/O wait for more than NUM seconds.

syzbot
2026-05-01T14:48:23Z

syzbot has found a reproducer for the following issue on:

HEAD commit: 26fd6bff2c05 Merge tag 'mtd/fixes-for-7.1-rc2' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1229bece580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d0f0911eedbc130a
dashboard link: https://syzkaller.appspot.com/bug?extid=c7604c9fdd7580cca4e0
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17f37506580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=171441ce580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7d72741f9879/disk-26fd6bff.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b02c6a1eba87/vmlinux-26fd6bff.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4f218b09b68f/bzImage-26fd6bff.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c7604c9fdd7580cca4e0@syzkaller.appspotmail.com

INFO: task jbd2/sda1-8:4955 blocked in I/O wait for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:jbd2/sda1-8 state:D stack:26088 pid:4955 tgid:4955 ppid:2 task_flags:0x240040 flags:0x00080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5387 [inline]
__schedule+0x10e9/0x6820 kernel/sched/core.c:7188
__schedule_loop kernel/sched/core.c:7267 [inline]
schedule+0xdd/0x390 kernel/sched/core.c:7282
io_schedule+0x8a/0xf0 kernel/sched/core.c:8109
bit_wait_io+0xd/0xe0 kernel/sched/wait_bit.c:250
__wait_on_bit+0x65/0x180 kernel/sched/wait_bit.c:52
out_of_line_wait_on_bit+0xdc/0x110 kernel/sched/wait_bit.c:67
wait_on_bit_io include/linux/wait_bit.h:105 [inline]
__wait_on_buffer+0x64/0x70 fs/buffer.c:123
wait_on_buffer include/linux/buffer_head.h:420 [inline]
jbd2_journal_commit_transaction+0x388a/0x6870 fs/jbd2/commit.c:837
kjournald2+0x200/0x760 fs/jbd2/journal.c:201
kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
INFO: task syz.0.189:6070 blocked in I/O wait for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.189 state:D stack:28240 pid:6070 tgid:6070 ppid:5783 task_flags:0x440040 flags:0x00080002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5387 [inline]
__schedule+0x10e9/0x6820 kernel/sched/core.c:7188
__schedule_loop kernel/sched/core.c:7267 [inline]
schedule+0xdd/0x390 kernel/sched/core.c:7282
io_schedule+0x8a/0xf0 kernel/sched/core.c:8109
bit_wait_io+0xd/0xe0 kernel/sched/wait_bit.c:250
__wait_on_bit+0x65/0x180 kernel/sched/wait_bit.c:52
out_of_line_wait_on_bit+0xdc/0x110 kernel/sched/wait_bit.c:67
wait_on_bit_io include/linux/wait_bit.h:105 [inline]
do_get_write_access+0x84f/0x1220 fs/jbd2/transaction.c:1113
jbd2_journal_get_write_access+0x1d6/0x280 fs/jbd2/transaction.c:1263
__ext4_journal_get_write_access+0x6a/0x340 fs/ext4/ext4_jbd2.c:241
ext4_reserve_inode_write+0x1b7/0x330 fs/ext4/inode.c:6375
__ext4_mark_inode_dirty+0x18f/0x890 fs/ext4/inode.c:6550
ext4_dirty_inode+0xd9/0x130 fs/ext4/inode.c:6587
__mark_inode_dirty+0x1f3/0x1720 fs/fs-writeback.c:2623
generic_update_time fs/inode.c:2192 [inline]
file_update_time_flags+0x46b/0x500 fs/inode.c:2422
ext4_page_mkwrite+0x324/0x1890 fs/ext4/inode.c:6753
do_page_mkwrite+0x17a/0x440 mm/memory.c:3668
do_shared_fault mm/memory.c:5969 [inline]
do_fault+0x3b5/0x1750 mm/memory.c:6031
do_pte_missing mm/memory.c:4550 [inline]
handle_pte_fault mm/memory.c:6411 [inline]
__handle_mm_fault+0x187d/0x2a00 mm/memory.c:6549
handle_mm_fault+0x36d/0xa20 mm/memory.c:6718
do_user_addr_fault+0x5a3/0x12f0 arch/x86/mm/fault.c:1334
handle_page_fault arch/x86/mm/fault.c:1474 [inline]
exc_page_fault+0x6f/0xd0 arch/x86/mm/fault.c:1527
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
RIP: 0033:0x7f97a466a883
RSP: 002b:00007ffc3f813c60 EFLAGS: 00010246
RAX: 000000000003fde8 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000001b2e124000 RSI: 0000000000040000 RDI: 00007f97a49db710
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 00007ffc3f813ef0
</TASK>

Showing all locks held in the system:
1 lock held by ksoftirqd/1/23:
#0: ffff8880b853b3e0 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2c/0x140 kernel/sched/core.c:652
1 lock held by khungtaskd/30:
#0: ffffffff8e7e52e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#0: ffffffff8e7e52e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
#0: ffffffff8e7e52e0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6775
6 locks held by kworker/u8:3/47:
#0: ffff88801c6ca140 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x12d6/0x1980 kernel/workqueue.c:3277
#1: ffffc90000b77d08 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x973/0x1980 kernel/workqueue.c:3278
#2: ffff8880389060d8 (&type->s_umount_key#33){++++}-{4:4}, at: super_trylock_shared+0x1e/0xf0 fs/super.c:565
#3: ffff888038904c18 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: do_writepages+0x278/0x600 mm/page-writeback.c:2575
#4: ffff888038902938 (jbd2_handle){++++}-{0:0}, at: start_this_handle+0xfaa/0x13a0 fs/jbd2/transaction.c:444
#5: ffff88807928f290 (&ei->i_data_sem){++++}-{4:4}, at: ext4_map_blocks+0x45a/0xd30 fs/ext4/inode.c:823
2 locks held by getty/5383:
#0: ffff88802dace0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
#1: ffffc9000322b2e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x419/0x14f0 drivers/tty/n_tty.c:2211
3 locks held by syz.0.189/6070:
#0: ffff88807e006bc8 (vm_lock){++++}-{0:0}, at: lock_vma_under_rcu+0x11d/0x590 mm/mmap_lock.c:310
#1: ffff888038906508 (sb_pagefaults){.+.+}-{0:0}, at: do_page_mkwrite+0x17a/0x440 mm/memory.c:3668
#2: ffff888038902938 (jbd2_handle){++++}-{0:0}, at: start_this_handle+0xfaa/0x13a0 fs/jbd2/transaction.c:444
3 locks held by syz-executor/6077:
#0: ffff888038906410 (sb_writers#4){.+.+}-{0:0}, at: filename_create+0x10d/0x400 fs/namei.c:4943
#1: ffff8880792b1f98 (&type->i_mutex_dir_key#3/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1074 [inline]
#1: ffff8880792b1f98 (&type->i_mutex_dir_key#3/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2914 [inline]
#1: ffff8880792b1f98 (&type->i_mutex_dir_key#3/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2938 [inline]
#1: ffff8880792b1f98 (&type->i_mutex_dir_key#3/1){+.+.}-{4:4}, at: filename_create+0x1c0/0x400 fs/namei.c:4950
#2: ffff888038902938 (jbd2_handle){++++}-{0:0}, at: start_this_handle+0xfaa/0x13a0 fs/jbd2/transaction.c:444

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 30 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
nmi_cpu_backtrace.cold+0x12d/0x151 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x1d7/0x230 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
__sys_info lib/sys_info.c:157 [inline]
sys_info+0x141/0x190 lib/sys_info.c:165
check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
watchdog+0xcb1/0x1030 kernel/hung_task.c:561
kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 1057 Comm: kworker/u8:7 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:smp_call_function_many_cond+0xdd4/0x1700 kernel/smp.c:871
Code: 00 00 0f 84 1e 05 00 00 e8 c9 6a 0c 00 83 c5 01 bf 07 00 00 00 48 63 dd 48 89 de e8 96 65 0c 00 48 83 fb 07 0f 86 22 fb ff ff <44> 8b 64 24 58 44 8b 7c 24 5c e8 9d 6a 0c 00 8b 5c 24 4c bf 01 00
RSP: 0018:ffffc90003d37870 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffffffff81fb686f
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888029b83d80
RBP: 0000000000000000 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffc90003d37958
R13: ffff8880b843c6c0 R14: ffff8880b843c601 R15: ffff8880b853c710
FS: 0000000000000000(0000) GS:ffff88812447d000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055a400fed660 CR3: 000000000e596000 CR4: 00000000003526f0
Call Trace:
<TASK>
on_each_cpu_cond_mask+0x40/0x90 kernel/smp.c:1057
on_each_cpu include/linux/smp.h:72 [inline]
smp_text_poke_sync_each_cpu arch/x86/kernel/alternative.c:2773 [inline]
smp_text_poke_batch_finish+0x976/0xc60 arch/x86/kernel/alternative.c:3045
arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
jump_label_update+0x37a/0x550 kernel/jump_label.c:910
static_key_enable_cpuslocked+0x1bc/0x270 kernel/jump_label.c:210
static_key_enable+0x1a/0x20 kernel/jump_label.c:223
toggle_allocation_gate mm/kfence/core.c:906 [inline]
toggle_allocation_gate+0xfe/0x2d0 mm/kfence/core.c:898
process_one_work+0xa0e/0x1980 kernel/workqueue.c:3302
process_scheduled_works kernel/workqueue.c:3385 [inline]
worker_thread+0x5ef/0xe50 kernel/workqueue.c:3466
kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
----------------
Code disassembly (best guess):
0: 00 00 add %al,(%rax)
2: 0f 84 1e 05 00 00 je 0x526
8: e8 c9 6a 0c 00 call 0xc6ad6
d: 83 c5 01 add $0x1,%ebp
10: bf 07 00 00 00 mov $0x7,%edi
15: 48 63 dd movslq %ebp,%rbx
18: 48 89 de mov %rbx,%rsi
1b: e8 96 65 0c 00 call 0xc65b6
20: 48 83 fb 07 cmp $0x7,%rbx
24: 0f 86 22 fb ff ff jbe 0xfffffb4c
* 2a: 44 8b 64 24 58 mov 0x58(%rsp),%r12d <-- trapping instruction
2f: 44 8b 7c 24 5c mov 0x5c(%rsp),%r15d
34: e8 9d 6a 0c 00 call 0xc6ad6
39: 8b 5c 24 4c mov 0x4c(%rsp),%ebx
3d: bf .byte 0xbf
3e: 01 00 add %eax,(%rax)

---
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