INFO: task hung in fuse_simple_request (2)

Status: upstream: reported syz repro on 2025/10/25 20:31
Bug presence: origin:upstream
Labels: missing-backport
[Documentation on labels]
Reported-by: syzbot+0372270e0e72337a801e@syzkaller.appspotmail.com
First crash: 375d, last: 4d18h
▶ ▼ Bug presence (3)
Date Name Commit Repro Result
2026/10/31 linux-6.6.y (ToT) b5a1dc3ad482 syz [report] INFO: task hung in fuse_simple_request
2026/05/11 upstream (ToT) 5d6919055dec syz [report] INFO: task hung in __fuse_simple_request
2026/10/31 upstream (ToT) 2a500a04d6f9 syz Didn't crash
▶ ▼ Similar bugs (10)
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 746d 864d 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 335d 375d 0/3 auto-obsoleted due to no activity on 2026/03/15 05:05
linux-5.15 INFO: task hung in fuse_simple_request 1 12 1105d 1203d 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 477d 477d 0/2 auto-obsoleted due to no activity on 2025/10/23 13:22
upstream INFO: task hung in fuse_simple_request fuse 1 syz, C inconclusive error 273 772d 2152d 0/29 upstream: reported C repro on 2020/12/13 21:13
linux-5.15 INFO: task hung in fuse_simple_request (5) 1 1 87d 87d 0/3 upstream: reported on 2026/08/09 12:03
linux-6.1 INFO: task hung in fuse_simple_request 1 6 1082d 1171d 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 500d 614d 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 error 27 266d 866d 0/3 upstream: reported syz repro on 2024/06/21 20:45
upstream INFO: task can't die in request_wait_answer fuse 1 syz, C error 14 1723d 2233d 0/29 auto-obsoleted due to no activity on 2023/04/16 22:02
▶ ▼ Fix bisection attempts (1)
Created Duration User Patch Repo Result
2026/07/24 16:50 2h29m bisect fix linux-6.6.y OK (0) job log log

Sample crash report:
INFO: task syz.0.17:5948 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.17        state:D stack:25384 pid:5948  ppid:5904   flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 request_wait_answer fs/fuse/dev.c:407 [inline]
 __fuse_request_send fs/fuse/dev.c:426 [inline]
 fuse_simple_request+0x11e8/0x1c40 fs/fuse/dev.c:513
 fuse_flush+0x667/0x8b0 fs/fuse/file.c:549
 filp_flush fs/open.c:1533 [inline]
 filp_close+0xb1/0x150 fs/open.c:1546
 __range_close fs/file.c:698 [inline]
 __close_range+0x379/0x690 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:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f46b219ce59
RSP: 002b:00007ffe971e5598 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: ffffffffffffffda RBX: 00007f46b2417da0 RCX: 00007f46b219ce59
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f46b2417da0 R08: 0000000000000006 R09: 0000000000000000
R10: 00007f46b2417cb0 R11: 0000000000000246 R12: 0000000000028a2f
R13: 00007f46b2415fac R14: 00000000000287cc R15: 00007f46b2415fa0
 </TASK>
INFO: task syz.0.17:5950 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.17        state:D stack:26824 pid:5950  ppid:5904   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 request_wait_answer fs/fuse/dev.c:407 [inline]
 __fuse_request_send fs/fuse/dev.c:426 [inline]
 fuse_simple_request+0x11e8/0x1c40 fs/fuse/dev.c:513
 fuse_do_getattr+0x38c/0x6d0 fs/fuse/dir.c:1269
 fuse_update_get_attr+0x62d/0x1090 fs/fuse/dir.c:1326
 vfs_getattr fs/stat.c:176 [inline]
 vfs_statx+0x1ac/0x680 fs/stat.c:248
 vfs_fstatat+0x12a/0x1b0 fs/stat.c:299
 __do_sys_newfstatat fs/stat.c:463 [inline]
 __se_sys_newfstatat fs/stat.c:457 [inline]
 __x64_sys_newfstatat+0x149/0x1f0 fs/stat.c:457
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f46b219ce59
RSP: 002b:00007f46b30d1028 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
RAX: ffffffffffffffda RBX: 00007f46b2416090 RCX: 00007f46b219ce59
RDX: 0000000000000000 RSI: 00002000000008c0 RDI: ffffffffffffff9c
RBP: 00007f46b2232e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f46b2416128 R14: 00007f46b2416090 R15: 00007ffe971e5438
 </TASK>

Showing all locks held in the system:
5 locks held by kworker/u4:1/12:
1 lock held by khungtaskd/29:
 #0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
4 locks held by kworker/u4:3/48:
2 locks held by getty/5528:
 #0: ffff8880310320a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x428/0x1370 drivers/tty/n_tty.c:2217

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

NMI backtrace for cpu 0
CPU: 0 PID: 29 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a6/0x3e0 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+0xf59/0xfa0 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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 48 Comm: kworker/u4:3 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Workqueue: bat_events batadv_nc_worker
RIP: 0010:check_region_inline mm/kasan/generic.c:-1 [inline]
RIP: 0010:kasan_check_range+0x10/0x290 mm/kasan/generic.c:187
Code: c0 c3 0f 0b b8 ea ff ff ff c3 0f 0b b8 ea ff ff ff c3 cc cc cc cc cc cc cc cc 66 0f 1f 00 b0 01 48 85 f6 0f 84 b4 01 00 00 55 <41> 57 41 56 41 55 41 54 53 4c 8d 04 37 49 39 f8 0f 82 13 02 00 00
RSP: 0018:ffffc90000b8f7b0 EFLAGS: 00000002
RAX: 0000000000000001 RBX: 0000000000000001 RCX: ffffffff81681162
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff911bc5e8
RBP: ffffc90000b8fa08 R08: dffffc0000000000 R09: 1ffffffff22378bd
R10: dffffc0000000000 R11: fffffbfff22378be R12: 0000000000000000
R13: ffff88801d672928 R14: 000000000000076f R15: ffff88801d672928
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5bda1fdff8 CR3: 000000000cf32000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 instrument_atomic_read include/linux/instrumented.h:68 [inline]
 _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
 hlock_class kernel/locking/lockdep.c:228 [inline]
 check_wait_context kernel/locking/lockdep.c:4798 [inline]
 __lock_acquire+0x952/0x7d80 kernel/locking/lockdep.c:5087
 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
 rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 rcu_read_lock include/linux/rcupdate.h:786 [inline]
 batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:408 [inline]
 batadv_nc_worker+0xef/0x600 net/batman-adv/network-coding.c:719
 process_one_work kernel/workqueue.c:2653 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2730
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2811
 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>

Crashes (10):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/22 07:33 linux-6.6.y d1cfde2d5d15 43bfcdb0 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in fuse_simple_request
2026/05/10 06:11 linux-6.6.y 3b9f64db0496 29233ece .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in fuse_simple_request
2026/08/07 03:44 linux-6.6.y 80dfb0405055 c38879ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in fuse_simple_request
2026/05/31 15:28 linux-6.6.y 0a40c6fbd105 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in fuse_simple_request
2026/05/31 07:37 linux-6.6.y 0a40c6fbd105 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in fuse_simple_request
2026/05/19 08:29 linux-6.6.y eac8889a3a1c 9f74d399 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in fuse_simple_request
2026/03/01 12:13 linux-6.6.y 7a137e9bfa0e 43249bac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in fuse_simple_request
2026/02/11 23:18 linux-6.6.y 1b4ef5214f17 75707236 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in fuse_simple_request
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.