syzbot


INFO: task hung in fuse_simple_request (2)

Status: upstream: reported on 2025/10/25 20:31
Reported-by: syzbot+0372270e0e72337a801e@syzkaller.appspotmail.com
First crash: 48d, last: 8d02h
Similar bugs (9)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: task hung in fuse_simple_request (2) 1 3 419d 537d 0/3 auto-obsoleted due to no activity on 2025/01/28 01:40
linux-5.15 INFO: task hung in fuse_simple_request (4) 1 2 8d02h 48d 0/3 upstream: reported on 2025/10/25 20:54
linux-5.15 INFO: task hung in fuse_simple_request 1 12 778d 876d 0/3 auto-obsoleted due to no activity on 2024/02/03 13:59
linux-6.6 INFO: task hung in fuse_simple_request 1 1 150d 150d 0/2 auto-obsoleted due to no activity on 2025/10/23 13:22
upstream INFO: task hung in fuse_simple_request fuse 1 C inconclusive error 273 445d 1825d 0/29 upstream: reported C repro on 2020/12/13 21:13
linux-6.1 INFO: task hung in fuse_simple_request 1 6 755d 844d 0/3 auto-obsoleted due to no activity on 2024/02/26 14:29
linux-5.15 INFO: task hung in fuse_simple_request (3) 1 9 173d 287d 0/3 auto-obsoleted due to no activity on 2025/09/30 15:49
linux-6.1 INFO: task hung in fuse_simple_request (2) origin:upstream 1 syz 26 8d01h 539d 0/3 upstream: reported syz repro on 2024/06/21 20:45
upstream INFO: task can't die in request_wait_answer fuse 1 C error 14 1396d 1906d 0/29 auto-obsoleted due to no activity on 2023/04/16 22:02

Sample crash report:
INFO: task syz.0.487:7994 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.487       state:D stack:24232 pid:7994  ppid:5794   flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 request_wait_answer fs/fuse/dev.c:407 [inline]
 __fuse_request_send fs/fuse/dev.c:426 [inline]
 fuse_simple_request+0x1195/0x1bb0 fs/fuse/dev.c:513
 fuse_flush+0x5b0/0x830 fs/fuse/file.c:537
 filp_flush fs/open.c:1533 [inline]
 filp_close+0xb1/0x150 fs/open.c:1546
 __range_close fs/file.c:698 [inline]
 __close_range+0x342/0x630 fs/file.c:755
 __do_sys_close_range fs/open.c:1599 [inline]
 __se_sys_close_range fs/open.c:1596 [inline]
 __x64_sys_close_range+0x7a/0x90 fs/open.c:1596
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f0f28f8f749
RSP: 002b:00007ffc4e2397b8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: ffffffffffffffda RBX: 00007f0f291e7da0 RCX: 00007f0f28f8f749
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f0f291e7da0 R08: 0000000000000090 R09: 000000084e239aaf
R10: 00000000003ffd4c R11: 0000000000000246 R12: 000000000004bf78
R13: 00007f0f291e6180 R14: ffffffffffffffff R15: 00007ffc4e2398d0
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/29:
 #0: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #0: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #0: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
3 locks held by kworker/u4:6/1328:
2 locks held by getty/5549:
 #0: ffff8880316480a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000328b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x425/0x1380 drivers/tty/n_tty.c:2217
2 locks held by kworker/1:3/5778:
 #0: ffff888017870938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
 #0: ffff888017870938 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
 #1: ffffc90004557d00 (free_ipc_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
 #1: ffffc90004557d00 (free_ipc_work){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
1 lock held by syz-executor/5786:
 #0: ffffffff8cd358f8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:324 [inline]
 #0: ffffffff8cd358f8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x360/0x830 kernel/rcu/tree_exp.h:1004
2 locks held by kworker/1:6/5858:
 #0: ffff888017872538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
 #0: ffff888017872538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
 #1: ffffc90004a8fd00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
 #1: ffffc90004a8fd00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
3 locks held by kworker/0:5/5876:
1 lock held by syz-executor/8171:

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

NMI backtrace for cpu 1
CPU: 1 PID: 29 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x39b/0x3d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x2f0 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+0xf41/0xf80 kernel/hung_task.c:379
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 6193 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:native_save_fl arch/x86/include/asm/irqflags.h:32 [inline]
RIP: 0010:arch_local_save_flags arch/x86/include/asm/irqflags.h:89 [inline]
RIP: 0010:arch_local_irq_save arch/x86/include/asm/irqflags.h:107 [inline]
RIP: 0010:debug_check_no_locks_freed+0xc4/0x3c0 kernel/locking/lockdep.c:6582
Code: 7b 02 00 00 83 3d f7 21 e3 0c 00 0f 84 66 01 00 00 48 89 5c 24 38 48 c7 84 24 80 00 00 00 00 00 00 00 9c 8f 84 24 80 00 00 00 <48> 8b 84 24 80 00 00 00 48 89 44 24 30 fa 4c 89 74 24 28 49 8d 9e
RSP: 0018:ffffc9000b2f7140 EFLAGS: 00000202
RAX: 0000000000000000 RBX: 1ffff9200165ee30 RCX: 0000000000000000
RDX: dffffc0000000000 RSI: 0000000000001000 RDI: ffff88804bb86000
RBP: ffffc9000b2f7240 R08: ffffffff8e4a93ef R09: 1ffffffff1c9527d
R10: dffffc0000000000 R11: fffffbfff1c9527e R12: ffff88804bb86000
R13: 0000000000001000 R14: ffff88802e078000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055b1e5a73000 CR3: 000000002dabb000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 free_pages_prepare mm/page_alloc.c:1158 [inline]
 free_unref_page_prepare+0x1d3/0x8e0 mm/page_alloc.c:2336
 free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2475
 release_pages+0x1fa0/0x2220 mm/swap.c:1022
 __folio_batch_release+0x71/0xe0 mm/swap.c:1042
 folio_batch_release include/linux/pagevec.h:83 [inline]
 shmem_undo_range+0x5d0/0x1a40 mm/shmem.c:1026
 shmem_truncate_range mm/shmem.c:1135 [inline]
 shmem_evict_inode+0x273/0xa70 mm/shmem.c:1264
 evict+0x486/0x870 fs/inode.c:705
 __dentry_kill+0x431/0x650 fs/dcache.c:611
 shrink_dentry_list+0x39f/0x6a0 fs/dcache.c:1206
 shrink_dcache_parent+0xac/0x3c0 fs/dcache.c:-1
 do_one_tree+0x23/0xe0 fs/dcache.c:1686
 shrink_dcache_for_umount+0x69/0x110 fs/dcache.c:1703
 generic_shutdown_super+0x67/0x2b0 fs/super.c:665
 kill_anon_super fs/super.c:1303 [inline]
 kill_litter_super+0x76/0xb0 fs/super.c:1313
 deactivate_locked_super+0x97/0x100 fs/super.c:481
 cleanup_mnt+0x429/0x4c0 fs/namespace.c:1259
 task_work_run+0x1ce/0x250 kernel/task_work.c:239
 exit_task_work include/linux/task_work.h:43 [inline]
 do_exit+0x90b/0x23c0 kernel/exit.c:883
 do_group_exit+0x21b/0x2d0 kernel/exit.c:1024
 __do_sys_exit_group kernel/exit.c:1035 [inline]
 __se_sys_exit_group kernel/exit.c:1033 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1033
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd65bd8f749
Code: Unable to access opcode bytes at 0x7fd65bd8f71f.
RSP: 002b:00007ffded5e4718 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007fd65be1585d RCX: 00007fd65bd8f749
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000043
RBP: 00007fd65be1586f R08: 00007ffded5e24b7 R09: 00000000000927c0
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00000000000927c0 R14: 0000000000070fb6 R15: 00007ffded5e48c0
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/05 05:11 linux-6.6.y 4791134e4aeb d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in fuse_simple_request
2025/10/25 20:31 linux-6.6.y 4a243110dc88 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in fuse_simple_request
* Struck through repros no longer work on HEAD.