syzbot

INFO: task kworker/u4:3:46 blocked for more than 143 seconds.
      Not tainted 6.1.90-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:3    state:D stack:19224 pid:46    ppid:2      flags:0x00004000
Workqueue: writeback wb_workfn (flush-7:0)
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5245 [inline]
 __schedule+0x142d/0x4550 kernel/sched/core.c:6558
 schedule+0xbf/0x180 kernel/sched/core.c:6634
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6693
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0x6b9/0xd80 kernel/locking/mutex.c:747
 exfat_write_inode+0x65/0x110 fs/exfat/inode.c:94
 write_inode fs/fs-writeback.c:1460 [inline]
 __writeback_single_inode+0x67d/0x11e0 fs/fs-writeback.c:1677
 writeback_sb_inodes+0xc2b/0x1b20 fs/fs-writeback.c:1903
 __writeback_inodes_wb+0x114/0x400 fs/fs-writeback.c:1974
 wb_writeback+0x4b1/0xe10 fs/fs-writeback.c:2079
 wb_check_background_flush fs/fs-writeback.c:2145 [inline]
 wb_do_writeback fs/fs-writeback.c:2233 [inline]
 wb_workfn+0xc9e/0x1020 fs/fs-writeback.c:2260
 process_one_work+0x8a9/0x11d0 kernel/workqueue.c:2292
 worker_thread+0xa47/0x1200 kernel/workqueue.c:2439
 kthread+0x28d/0x320 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
 </TASK>

Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/12:
 #0: ffffffff8d12ae50 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x29/0xe30 kernel/rcu/tasks.h:516
1 lock held by rcu_tasks_trace/13:
 #0: ffffffff8d12b650 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x29/0xe30 kernel/rcu/tasks.h:516
1 lock held by khungtaskd/28:
 #0: ffffffff8d12ac80 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 #0: ffffffff8d12ac80 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
 #0: ffffffff8d12ac80 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6494
4 locks held by kworker/u4:3/46:
 #0: ffff888142eee938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7a9/0x11d0 kernel/workqueue.c:2267
 #1: ffffc90000b77d20 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7a9/0x11d0 kernel/workqueue.c:2267
 #2: ffff88807a8fe0e0 (&type->s_umount_key#42){.+.+}-{3:3}, at: trylock_super+0x1b/0xf0 fs/super.c:415
 #3: ffff88807a8fc0e0 (&sbi->s_lock){+.+.}-{3:3}, at: exfat_write_inode+0x65/0x110 fs/exfat/inode.c:94
2 locks held by getty/3304:
 #0: ffff888028bbb098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
 #1: ffffc900031332f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6a7/0x1db0 drivers/tty/n_tty.c:2188
3 locks held by syz-executor204/3585:

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

NMI backtrace for cpu 0
CPU: 0 PID: 28 Comm: khungtaskd Not tainted 6.1.90-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
 nmi_cpu_backtrace+0x4e1/0x560 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x1b0/0x3f0 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+0xf88/0xfd0 kernel/hung_task.c:377
 kthread+0x28d/0x320 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 3585 Comm: syz-executor204 Not tainted 6.1.90-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
RIP: 0010:__this_cpu_preempt_check+0x0/0x10 lib/smp_processor_id.c:65
Code: 4c 89 fe 4c 89 f2 e8 4f e3 fd ff 48 8b 74 24 30 48 c7 c7 60 44 3d 8b e8 3e e3 fd ff e8 15 9b ff ff eb a9 e8 92 e6 ff ff 66 90 <48> 89 fe 48 c7 c7 e0 43 3d 8b e9 e1 fe ff ff cc eb 1e 0f 1f 00 48
RSP: 0018:ffffc90003cff598 EFLAGS: 00000046
RAX: 0000000000000200 RBX: 0000000000000200 RCX: ffff888028c13b80
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8afa0180
RBP: ffffc90003cff6c8 R08: ffffffff82010392 R09: ffffed100e69bd69
R10: 0000000000000000 R11: dffffc0000000001 R12: 0000000000000000
R13: 1ffff9200079febc R14: 0000000000000200 R15: 0000000000036938
FS:  0000555556328380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055ae7cc55c78 CR3: 000000002280d000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <NMI>
 </NMI>
 <TASK>
 lookup_bh_lru fs/buffer.c:1274 [inline]
 __find_get_block+0x1ac/0x1120 fs/buffer.c:1303
 __getblk_gfp+0x2d/0xa20 fs/buffer.c:1329
 __bread_gfp+0x2a/0x370 fs/buffer.c:1367
 sb_bread include/linux/buffer_head.h:338 [inline]
 __exfat_ent_get fs/exfat/fatent.c:48 [inline]
 exfat_ent_get+0x149/0x400 fs/exfat/fatent.c:97
 exfat_readdir fs/exfat/dir.c:183 [inline]
 exfat_iterate+0xccc/0x3280 fs/exfat/dir.c:257
 iterate_dir+0x224/0x560
 __do_sys_getdents64 fs/readdir.c:369 [inline]
 __se_sys_getdents64+0x209/0x4f0 fs/readdir.c:354
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f993f5da0a3
Code: c1 66 0f 1f 44 00 00 48 83 c4 08 48 89 ef 5b 5d e9 82 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:00007fffc1323a48 EFLAGS: 00000293 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 0000555556331730 RCX: 00007f993f5da0a3
RDX: 0000000000008000 RSI: 0000555556331730 RDI: 0000000000000004
RBP: 0000555556331704 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000001000 R11: 0000000000000293 R12: ffffffffffffffb8
R13: 0000000000000010 R14: 0000555556331700 R15: 00007fffc1325cc0
 </TASK>
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.459 msecs