syzbot
INFO: task hung in do_get_write_access
Status:
upstream: reported C repro on 2026/08/05 00:11
Reported-by: syzbot+9e3d85789d3996cc829c@syzkaller.appspotmail.com
First crash: 6d10h, last: 12h28m
Sample crash report:
INFO: task syz.0.237:4672 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.237 state:D stack:27632 pid:4672 ppid:4401 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5246 [inline]
__schedule+0x107f/0x4030 kernel/sched/core.c:6563
schedule+0xb9/0x180 kernel/sched/core.c:6639
io_schedule+0x7c/0xd0 kernel/sched/core.c:8799
bit_wait_io+0xd/0xc0 kernel/sched/wait_bit.c:209
__wait_on_bit+0x9b/0x2c0 kernel/sched/wait_bit.c:49
out_of_line_wait_on_bit+0x138/0x190 kernel/sched/wait_bit.c:64
wait_on_bit_io include/linux/wait_bit.h:101 [inline]
do_get_write_access+0x605/0xf20 fs/jbd2/transaction.c:1115
jbd2_journal_get_write_access+0x108/0x140 fs/jbd2/transaction.c:1250
__ext4_journal_get_write_access+0x24b/0x6e0 fs/ext4/ext4_jbd2.c:235
ext4_reserve_inode_write+0x201/0x290 fs/ext4/inode.c:5945
__ext4_mark_inode_dirty+0x161/0x760 fs/ext4/inode.c:6119
ext4_dirty_inode+0xbf/0x100 fs/ext4/inode.c:6156
__mark_inode_dirty+0x2e7/0xe80 fs/fs-writeback.c:2500
generic_update_time fs/inode.c:1946 [inline]
inode_update_time fs/inode.c:1959 [inline]
__file_update_time+0x21d/0x240 fs/inode.c:2147
file_update_time+0x2f3/0x370 fs/inode.c:2178
ext4_page_mkwrite+0x1a9/0x10d0 fs/ext4/inode.c:6274
do_page_mkwrite+0x16b/0x5c0 mm/memory.c:3009
do_shared_fault mm/memory.c:4694 [inline]
do_fault mm/memory.c:4762 [inline]
handle_pte_fault mm/memory.c:5029 [inline]
__handle_mm_fault mm/memory.c:5171 [inline]
handle_mm_fault+0x199c/0x3d40 mm/memory.c:5292
do_user_addr_fault+0x58e/0xb20 arch/x86/mm/fault.c:1338
handle_page_fault arch/x86/mm/fault.c:1429 [inline]
exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1482
asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0033:0x7ff9b8a667f1
RSP: 002b:00007ffc33793840 EFLAGS: 00010202
RAX: 0000001b2fc64000 RBX: 0000000000000000 RCX: 000000000003fde8
RDX: 0000001b2fc63fff RSI: 0000000000000008 RDI: 00007ff9b9955720
RBP: 00007ff9b9955720 R08: 0000000000000000 R09: 00007ff9b8e26038
R10: 00007ff9b9955700 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000003
</TASK>
Showing all locks held in the system:
7 locks held by kworker/u4:0/9:
#0: ffff888019647938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#1: ffffc900000e7d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#2: ffff88807dc6e0e0 (&type->s_umount_key#31){++++}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
#3: ffff88807dc70c18 (&sbi->s_writepages_rwsem){.+.+}-{0:0}, at: ext4_writepages+0x213/0x2e70 fs/ext4/inode.c:2717
#4: ffff88807dc72990 (jbd2_handle){++++}-{0:0}, at: start_this_handle+0x2014/0x2240 fs/jbd2/transaction.c:463
#5: ffff8880727a0288 (&ei->i_data_sem){++++}-{3:3}, at: ext4_map_blocks+0x914/0x1a90 fs/ext4/inode.c:674
#6: ffffe8ffffd33c58 (&lg->lg_mutex){+.+.}-{3:3}, at: ext4_mb_group_or_file fs/ext4/mballoc.c:5306 [inline]
#6: ffffe8ffffd33c58 (&lg->lg_mutex){+.+.}-{3:3}, at: ext4_mb_initialize_context+0x7f0/0xb80 fs/ext4/mballoc.c:5349
1 lock held by rcu_tasks_kthre/12:
#0: ffffffff8cb2e4f0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xef0 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
#0: ffffffff8cb2ed10 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xef0 kernel/rcu/tasks.h:517
1 lock held by khungtaskd/27:
#0: ffffffff8cb2db60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
#0: ffffffff8cb2db60 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
#0: ffffffff8cb2db60 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6527
2 locks held by getty/4028:
#0: ffff8880301ac098 (&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+0x41e/0x1360 drivers/tty/n_tty.c:2198
3 locks held by syz.0.237/4672:
#0: ffff88807c10cc58 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:136 [inline]
#0: ffff88807c10cc58 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5320 [inline]
#0: ffff88807c10cc58 (&mm->mmap_lock){++++}-{3:3}, at: lock_mm_and_find_vma+0x2e/0x2f0 mm/memory.c:5382
#1: ffff88807dc6e558 (sb_pagefaults){.+.+}-{0:0}, at: __sb_start_write include/linux/fs.h:1891 [inline]
#1: ffff88807dc6e558 (sb_pagefaults){.+.+}-{0:0}, at: sb_start_pagefault include/linux/fs.h:1995 [inline]
#1: ffff88807dc6e558 (sb_pagefaults){.+.+}-{0:0}, at: ext4_page_mkwrite+0x192/0x10d0 fs/ext4/inode.c:6273
#2: ffff88807dc72990 (jbd2_handle){++++}-{0:0}, at: start_this_handle+0x2014/0x2240 fs/jbd2/transaction.c:463
2 locks held by syz-executor/4673:
#0: ffff88807dc6e460 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x3d/0x90 fs/namespace.c:402
#1: ffff8880746b3628 (&type->i_mutex_dir_key#3/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:793 [inline]
#1: ffff8880746b3628 (&type->i_mutex_dir_key#3/1){+.+.}-{3:3}, at: filename_create+0x20b/0x450 fs/namei.c:3884
=============================================
NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<TASK>
dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
nmi_cpu_backtrace+0x3e6/0x460 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+0xf0e/0xf50 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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 64 Comm: kworker/u4:4 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: events_unbound cfg80211_wiphy_work
RIP: 0010:check_preemption_disabled+0x1/0x110 lib/smp_processor_id.c:13
Code: 80 a3 bc 8c 4c 89 f6 e8 dd 53 0d fa e9 6e ff ff ff 00 00 cc cc 00 00 cc cc 48 c7 c7 80 5d df 8a 48 c7 c6 c0 5d df 8a eb 00 55 <41> 57 41 56 53 48 83 ec 10 65 48 8b 04 25 28 00 00 00 48 89 44 24
RSP: 0018:ffffc900015b79f0 EFLAGS: 00000046
RAX: 1ffff110032768da RBX: 383630c611630b32 RCX: 0000000000000001
RDX: 0000000000000004 RSI: ffffffff8a8c2920 RDI: ffffffff8adf5de0
RBP: ffffc900015b7b08 R08: ffffffff8e210aef R09: 1ffffffff1c4215d
R10: dffffc0000000000 R11: fffffbfff1c4215e R12: ffff8880193b4780
R13: dffffc0000000000 R14: ffff8880193b46d0 R15: 1ffff920002b6f4c
FS: 0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1b1cebf400 CR3: 000000000c88e000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
lockdep_recursion_finish kernel/locking/lockdep.c:467 [inline]
lock_release+0x558/0x920 kernel/locking/lockdep.c:5698
__raw_spin_unlock include/linux/spinlock_api_smp.h:141 [inline]
_raw_spin_unlock+0x12/0x40 kernel/locking/spinlock.c:186
spin_unlock include/linux/spinlock.h:391 [inline]
kcov_remote_start+0x145/0x7e0 kernel/kcov.c:886
kcov_remote_start_common include/linux/kcov.h:50 [inline]
ieee80211_iface_work+0x1f5/0xc70 net/mac80211/iface.c:1728
cfg80211_wiphy_work+0x224/0x260 net/wireless/core.c:433
process_one_work+0x8ab/0x1160 kernel/workqueue.c:2292
worker_thread+0xaf5/0x12a0 kernel/workqueue.c:2439
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
Struck through repros no longer work on HEAD.