syzbot


INFO: task hung in fuse_simple_request (2)

Status: upstream: reported syz repro on 2025/10/25 20:31
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+0372270e0e72337a801e@syzkaller.appspotmail.com
First crash: 227d, last: 9d09h
Bug presence (1)
Date Name Commit Repro Result
2026/05/11 upstream (ToT) 5d6919055dec syz [report] INFO: task hung in __fuse_simple_request
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 597d 715d 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 186d 227d 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 957d 1055d 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 329d 329d 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 624d 2004d 0/29 upstream: reported C repro on 2020/12/13 21:13
linux-6.1 INFO: task hung in fuse_simple_request 1 6 934d 1022d 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 352d 465d 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 118d 718d 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 1575d 2085d 0/29 auto-obsoleted due to no activity on 2023/04/16 22:02

Sample crash report:
INFO: task syz.0.17:5951 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:25544 pid:5951  ppid:5907   flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 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+0x1204/0x1c70 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+0x368/0x660 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+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f06ed19cdd9
RSP: 002b:00007ffcefbe95d8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: ffffffffffffffda RBX: 00007ffcefbe96c0 RCX: 00007f06ed19cdd9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 000000000002834e R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b2d220000 R11: 0000000000000246 R12: 00007ffcefbe9700
R13: 00007f06ed415fac R14: 00000000000283d5 R15: 00007f06ed415fa0
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/29:
 #0: ffffffff8d1320e0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #0: ffffffff8d1320e0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #0: ffffffff8d1320e0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
4 locks held by kworker/u4:8/2115:
3 locks held by kworker/u4:9/2915:
2 locks held by getty/5527:
 #0: ffff88814c7ce0a0 (&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+0x433/0x1390 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 04/18/2026
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+0xf3d/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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 12 Comm: kworker/u4:1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: events_unbound cfg80211_wiphy_work
RIP: 0010:get_current arch/x86/include/asm/current.h:41 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x8/0x60 kernel/kcov.c:215
Code: 00 00 f3 0f 1e fa 53 48 89 fb e8 13 00 00 00 48 8b 3d dc f9 03 0d 48 89 de 5b e9 d3 67 57 00 cc cc cc f3 0f 1e fa 48 8b 04 24 <65> 48 8b 0d b0 93 7c 7e 65 8b 15 b1 93 7c 7e 81 e2 00 01 ff 00 74
RSP: 0018:ffffc90000117150 EFLAGS: 00000246
RAX: ffffffff813b4175 RBX: ffffffff8f19e1e2 RCX: 0000000000000003
RDX: ffffffff813b3f02 RSI: ffffffff8cfa07e0 RDI: 0000000000000004
RBP: ffffc90000117278 R08: ffff88801b27da00 R09: 0000000000000008
R10: 0000000000000009 R11: 0000000000000000 R12: ffffc90000117228
R13: dffffc0000000000 R14: 0000000000000004 R15: ffffffff8f19e1e6
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005555692014e8 CR3: 000000000cf32000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 unwind_next_frame+0x9b5/0x2970 arch/x86/kernel/unwind_orc.c:521
 arch_stack_walk+0x144/0x190 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0xaa/0x100 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
 kasan_kmalloc include/linux/kasan.h:198 [inline]
 __do_kmalloc_node mm/slab_common.c:1007 [inline]
 __kmalloc+0xb4/0x230 mm/slab_common.c:1020
 kmalloc include/linux/slab.h:604 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 ieee802_11_parse_elems_full+0xb9/0x20c0 net/mac80211/util.c:1616
 ieee802_11_parse_elems_crc net/mac80211/ieee80211_i.h:2337 [inline]
 ieee802_11_parse_elems net/mac80211/ieee80211_i.h:2344 [inline]
 ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1609 [inline]
 ieee80211_ibss_rx_queued_mgmt+0x4b5/0x2c80 net/mac80211/ibss.c:1642
 ieee80211_iface_process_skb net/mac80211/iface.c:1655 [inline]
 ieee80211_iface_work+0x717/0xc70 net/mac80211/iface.c:1709
 cfg80211_wiphy_work+0x225/0x260 net/wireless/core.c:437
 process_one_work kernel/workqueue.c:2653 [inline]
 process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
 worker_thread+0xa55/0xfc0 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 (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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
2026/05/31 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.