syzbot

INFO: task kworker/u8:7:2856 blocked for more than 143 seconds.
      Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:7    state:D stack:23848 pid:2856  tgid:2856  ppid:2      flags:0x00004000
Workqueue: writeback wb_workfn (flush-7:0)
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5409 [inline]
 __schedule+0x1781/0x49d0 kernel/sched/core.c:6736
 __schedule_loop kernel/sched/core.c:6813 [inline]
 schedule+0x14b/0x320 kernel/sched/core.c:6828
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6885
 __mutex_lock_common kernel/locking/mutex.c:684 [inline]
 __mutex_lock+0x6a4/0xd70 kernel/locking/mutex.c:752
 exfat_write_inode+0x69/0x120 fs/exfat/inode.c:105
 write_inode fs/fs-writeback.c:1498 [inline]
 __writeback_single_inode+0x69f/0xfd0 fs/fs-writeback.c:1715
 writeback_sb_inodes+0x8e4/0x1220 fs/fs-writeback.c:1941
 __writeback_inodes_wb+0x11b/0x260 fs/fs-writeback.c:2012
 wb_writeback+0x45b/0xc70 fs/fs-writeback.c:2119
 wb_check_background_flush fs/fs-writeback.c:2189 [inline]
 wb_do_writeback fs/fs-writeback.c:2277 [inline]
 wb_workfn+0xc33/0x1070 fs/fs-writeback.c:2304
 process_one_work kernel/workqueue.c:3254 [inline]
 process_scheduled_works+0xa00/0x1770 kernel/workqueue.c:3335
 worker_thread+0x86d/0xd70 kernel/workqueue.c:3416
 kthread+0x2f0/0x390 kernel/kthread.c:388
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/29:
 #0: ffffffff8e132020 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:298 [inline]
 #0: ffffffff8e132020 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:750 [inline]
 #0: ffffffff8e132020 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x2a0 kernel/locking/lockdep.c:6614
4 locks held by kworker/u8:7/2856:
 #0: ffff88801aacf148 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3229 [inline]
 #0: ffff88801aacf148 ((wq_completion)writeback){+.+.}-{0:0}, at: process_scheduled_works+0x8e0/0x1770 kernel/workqueue.c:3335
 #1: ffffc9000adafd00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3230 [inline]
 #1: ffffc9000adafd00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x91b/0x1770 kernel/workqueue.c:3335
 #2: ffff8880776c00e0 (&type->s_umount_key#44){.+.+}-{3:3}, at: super_trylock_shared+0x22/0xf0 fs/super.c:561
 #3: ffff8880243ec0e0 (&sbi->s_lock){+.+.}-{3:3}, at: exfat_write_inode+0x69/0x120 fs/exfat/inode.c:105
2 locks held by getty/4811:
 #0: ffff88802f5c90a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90002f162f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6b5/0x1e10 drivers/tty/n_tty.c:2201
3 locks held by syz-executor526/5058:

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

NMI backtrace for cpu 1
CPU: 1 PID: 29 Comm: khungtaskd Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 nmi_cpu_backtrace+0x49c/0x4d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x198/0x320 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
 watchdog+0xfb0/0xff0 kernel/hung_task.c:379
 kthread+0x2f0/0x390 kernel/kthread.c:388
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 5058 Comm: syz-executor526 Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
RIP: 0010:check_preemption_disabled+0x60/0x120 lib/smp_processor_id.c:19
Code: 00 48 3b 44 24 08 0f 85 ce 00 00 00 89 d8 48 83 c4 10 5b 41 5c 41 5e 41 5f c3 cc cc cc cc 48 c7 04 24 00 00 00 00 9c 8f 04 24 <f7> 04 24 00 02 00 00 74 c5 49 89 f6 49 89 ff 65 4c 8b 24 25 40 d0
RSP: 0018:ffffc900038af410 EFLAGS: 00000046
RAX: 0000000080000000 RBX: 0000000000000000 RCX: ffff88807f013c00
RDX: 0000000000000000 RSI: ffffffff8baac1e0 RDI: ffffffff8bfdff00
RBP: ffffc900038af5a8 R08: ffffffff8217705f R09: 1ffff1100f8029dc
R10: dffffc0000000000 R11: ffffed100f8029dd R12: 0000000000000246
R13: dffffc0000000000 R14: ffffffff82177076 R15: ffff88801d083980
FS:  0000555561aed380(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055746d6d7600 CR3: 000000001fe14000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <NMI>
 </NMI>
 <TASK>
 lockdep_hardirqs_off+0x75/0x110 kernel/locking/lockdep.c:4460
 trace_hardirqs_off+0x12/0x40 kernel/trace/trace_preemptirq.c:87
 lookup_bh_lru fs/buffer.c:1362 [inline]
 __find_get_block+0x176/0x10d0 fs/buffer.c:1397
 bdev_getblk+0x38/0x610 fs/buffer.c:1423
 __bread_gfp+0xac/0x430 fs/buffer.c:1474
 sb_bread include/linux/buffer_head.h:321 [inline]
 __exfat_ent_get fs/exfat/fatent.c:48 [inline]
 exfat_ent_get+0x14d/0x400 fs/exfat/fatent.c:97
 exfat_readdir fs/exfat/dir.c:187 [inline]
 exfat_iterate+0x1376/0x33e0 fs/exfat/dir.c:261
 wrap_directory_iterator+0x94/0xe0 fs/readdir.c:67
 iterate_dir+0x539/0x6f0 fs/readdir.c:110
 __do_sys_getdents64 fs/readdir.c:409 [inline]
 __se_sys_getdents64+0x20d/0x4f0 fs/readdir.c:394
 do_syscall_64+0xfb/0x240
 entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7f2ac62860a3
Code: c1 66 0f 1f 44 00 00 48 83 c4 08 48 89 ef 5b 5d e9 a2 48 fb ff 66 90 b8 ff ff ff 7f 48 39 c2 48 0f 47 d0 b8 d9 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 05 c3 0f 1f 40 00 48 c7 c2 b8 ff ff ff f7 d8
RSP: 002b:00007ffead525138 EFLAGS: 00000293 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 0000555561af6730 RCX: 00007f2ac62860a3
RDX: 0000000000008000 RSI: 0000555561af6730 RDI: 0000000000000004
RBP: 0000555561af6704 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000001000 R11: 0000000000000293 R12: ffffffffffffffb8
R13: 0000000000000010 R14: 0000555561af6700 R15: 00007ffead5273b0
 </TASK>
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.339 msecs