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INFO: task hung in fuse_flush (2)

Status: premoderation: reported on 2026/03/28 15:06
Reported-by: syzbot+9d657051ee1aa9362378@syzkaller.appspotmail.com
First crash: 58d, last: 27d
▶ ▼ Similar bugs (14)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-6-12 INFO: task hung in fuse_flush 1 2 219d 248d 0/1 auto-obsoleted due to no activity on 2026/01/16 20:08
upstream INFO: task hung in fuse_flush (5) fuse 1 3 442d 447d 0/29 auto-obsoleted due to no activity on 2025/06/08 10:49
linux-4.19 INFO: task hung in fuse_flush 1 1 1894d 1894d 0/1 auto-closed as invalid on 2021/07/16 16:14
linux-6.1 INFO: task hung in fuse_flush 1 1 452d 452d 0/3 auto-obsoleted due to no activity on 2025/06/08 05:58
upstream INFO: task hung in fuse_flush (2) fuse 1 2 1218d 1227d 0/29 auto-obsoleted due to no activity on 2023/04/24 00:25
upstream INFO: task hung in fuse_flush (4) fuse 1 6 555d 701d 0/29 auto-obsoleted due to no activity on 2025/02/15 08:56
upstream INFO: task hung in fuse_flush fuse 1 2 1663d 1751d 0/29 auto-closed as invalid on 2022/02/03 03:15
linux-6.1 INFO: task hung in fuse_flush (2) 1 1 351d 351d 0/3 auto-obsoleted due to no activity on 2025/09/17 09:24
linux-5.15 INFO: task hung in fuse_flush 1 1 702d 702d 0/3 auto-obsoleted due to no activity on 2024/09/30 23:08
linux-4.19 INFO: task hung in fuse_flush (2) 1 1 1703d 1703d 0/1 auto-closed as invalid on 2022/01/24 04:40
linux-4.14 INFO: task hung in fuse_flush 1 C inconclusive 19 1259d 1580d 0/1 upstream: reported C repro on 2022/01/26 21:17
linux-4.19 INFO: task hung in fuse_flush (3) 1 109 1217d 1579d 0/1 upstream: reported on 2022/01/27 11:57
upstream INFO: task hung in fuse_flush (3) fuse 1 1 971d 971d 0/29 auto-obsoleted due to no activity on 2023/12/26 21:09
linux-6.6 INFO: task hung in fuse_flush 1 1 104d 104d 0/2 auto-obsoleted due to no activity on 2026/05/21 19:59

Sample crash report:
INFO: task syz.3.1069:3322 blocked for more than 122 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.1069      state:D stack:0     pid:3322  tgid:3322  ppid:292    flags:0x00000006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:6026 [inline]
 __schedule+0x1399/0x1fa0 kernel/sched/core.c:7880
 __schedule_loop kernel/sched/core.c:7961 [inline]
 schedule+0xc5/0x240 kernel/sched/core.c:7976
 schedule_preempt_disabled+0x14/0x30 kernel/sched/core.c:8033
 rwsem_down_write_slowpath+0x5b0/0x1bb0 kernel/locking/rwsem.c:1239
 __down_write_common kernel/locking/rwsem.c:1383 [inline]
 __down_write kernel/locking/rwsem.c:1392 [inline]
 down_write+0x163/0x2b0 kernel/locking/rwsem.c:1659
 inode_lock include/linux/fs.h:817 [inline]
 fuse_flush+0x799/0x2020 fs/fuse/file.c:580
 filp_flush fs/open.c:1552 [inline]
 filp_close+0xc0/0x160 fs/open.c:1565
 __range_close fs/file.c:726 [inline]
 __close_range+0x344/0x4e0 fs/file.c:796
 __do_sys_close_range fs/open.c:1618 [inline]
 __se_sys_close_range fs/open.c:1615 [inline]
 __x64_sys_close_range+0x7e/0x90 fs/open.c:1615
 x64_sys_call+0x1686/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:437
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7fca0ef9cdd9
RSP: 002b:00007ffcac43df18 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: ffffffffffffffda RBX: 00007fca0f217da0 RCX: 00007fca0ef9cdd9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007fca0f217da0 R08: 0000000000000006 R09: 0000000000000000
R10: 00007fca0f217cb0 R11: 0000000000000246 R12: 000000000002cf6f
R13: 00007fca0f21609c R14: 000000000002cd52 R15: 00007fca0f216090
 </TASK>
INFO: task syz.3.1069:3323 blocked for more than 128 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.1069      state:D stack:0     pid:3323  tgid:3322  ppid:292    flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:6026 [inline]
 __schedule+0x1399/0x1fa0 kernel/sched/core.c:7880
 __schedule_loop kernel/sched/core.c:7961 [inline]
 schedule+0xc5/0x240 kernel/sched/core.c:7976
 schedule_timeout+0xc7/0x3b0 kernel/time/timer.c:2596
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common kernel/sched/completion.c:116 [inline]
 wait_for_common+0x369/0x650 kernel/sched/completion.c:127
 wait_for_completion+0x1c/0x40 kernel/sched/completion.c:148
 fuse_direct_IO+0xa05/0x1310 fs/fuse/file.c:3268
 generic_file_direct_write+0x192/0x3b0 mm/filemap.c:4219
 fuse_cache_write_iter fs/fuse/file.c:1530 [inline]
 fuse_file_write_iter+0x1800/0x2830 fs/fuse/file.c:1869
 do_iter_readv_writev+0x62f/0x820 fs/read_write.c:-1
 vfs_writev+0x4a8/0xe50 fs/read_write.c:1076
 do_writev+0x151/0x2e0 fs/read_write.c:1123
 __do_sys_writev fs/read_write.c:1196 [inline]
 __se_sys_writev fs/read_write.c:1193 [inline]
 __x64_sys_writev+0x81/0x90 fs/read_write.c:1193
 x64_sys_call+0x1fbb/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:21
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7fca0ef9cdd9
RSP: 002b:00007fca0d9f7028 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007fca0f215fa0 RCX: 00007fca0ef9cdd9
RDX: 0000000000000020 RSI: 0000200000000400 RDI: 0000000000000005
RBP: 00007fca0f032d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fca0f216038 R14: 00007fca0f215fa0 R15: 00007ffcac43ddb8
 </TASK>
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 37 Comm: khungtaskd Not tainted syzkaller #0 4fe7cc6f12681e33e5673a6fddc2b9988498c256
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x140/0x1c0 lib/dump_stack.c:120
 dump_stack+0x19/0x20 lib/dump_stack.c:129
 nmi_cpu_backtrace+0x2ba/0x2d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x142/0x2c0 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:41
 trigger_all_cpu_backtrace include/linux/nmi.h:158 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:267 [inline]
 watchdog+0xdad/0xf00 kernel/hung_task.c:423
 kthread+0x2c9/0x370 kernel/kthread.c:389
 ret_from_fork+0x67/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 306 Comm: kworker/1:2 Not tainted syzkaller #0 4fe7cc6f12681e33e5673a6fddc2b9988498c256
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: events_power_efficient neigh_periodic_work
RIP: 0010:find_match+0x59/0x10e0 net/ipv6/route.c:778
Code: 00 00 fc ff df e8 57 8c 8d fc 48 89 5d d0 48 83 c3 17 48 89 d8 48 c1 e8 03 42 0f b6 04 38 84 c0 0f 85 9a 0c 00 00 44 0f b6 3b <44> 89 fe 83 e6 01 31 ff e8 2a 8f 8d fc 44 89 f8 83 e0 01 0f 85 c8
RSP: 0018:ffffc900002301f8 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff88810bbf60d7 RCX: ffff88810a335f00
RDX: 0000000000000100 RSI: 0000000000000001 RDI: ffff88810bbf60c0
RBP: ffffc900002302b0 R08: ffffc90000230540 R09: ffffc90000230550
R10: ffffc900002306b0 R11: fffff520000460da R12: 0000000000000001
R13: ffffc90000230540 R14: 0000000000000003 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f68220db6ac CR3: 000000010cb12000 CR4: 00000000003526b0
Call Trace:
 <IRQ>
 __find_rr_leaf+0x24e/0x840 net/ipv6/route.c:869
 find_rr_leaf net/ipv6/route.c:890 [inline]
 rt6_select net/ipv6/route.c:934 [inline]
 fib6_table_lookup+0x2ee/0x9e0 net/ipv6/route.c:2242
 ip6_pol_route+0x17a/0x1370 net/ipv6/route.c:2278
 ip6_pol_route_input+0x5a/0x80 net/ipv6/route.c:2335
 pol_lookup_func include/net/ip6_fib.h:626 [inline]
 fib6_rule_lookup+0x4ee/0x6d0 net/ipv6/fib6_rules.c:117
 ip6_route_input_lookup net/ipv6/route.c:2347 [inline]
 ip6_route_input+0x62e/0x8f0 net/ipv6/route.c:2643
 ip6_rcv_finish_core net/ipv6/ip6_input.c:66 [inline]
 ip6_rcv_finish+0x15a/0x3c0 net/ipv6/ip6_input.c:77
 NF_HOOK include/linux/netfilter.h:317 [inline]
 ipv6_rcv+0xf1/0x240 net/ipv6/ip6_input.c:309
 __netif_receive_skb_one_core net/core/dev.c:5789 [inline]
 __netif_receive_skb net/core/dev.c:5902 [inline]
 process_backlog+0x44b/0xad0 net/core/dev.c:6238
 __napi_poll+0xd3/0x610 net/core/dev.c:6889
 napi_poll net/core/dev.c:6958 [inline]
 net_rx_action+0x5ea/0xd80 net/core/dev.c:7080
 handle_softirqs+0x1aa/0x630 kernel/softirq.c:621
 __do_softirq+0xf/0x16 kernel/softirq.c:659
 do_softirq+0xb8/0x110 kernel/softirq.c:503
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x74/0x80 kernel/softirq.c:430
 __raw_write_unlock_bh include/linux/rwlock_api_smp.h:281 [inline]
 _raw_write_unlock_bh+0x33/0x70 kernel/locking/spinlock.c:366
 neigh_periodic_work+0xa73/0xbc0 net/core/neighbour.c:1024
 process_one_work kernel/workqueue.c:3261 [inline]
 process_scheduled_works+0x7d4/0x1020 kernel/workqueue.c:3342
 worker_thread+0xc51/0x1370 kernel/workqueue.c:3423
 kthread+0x2c9/0x370 kernel/kthread.c:389
 ret_from_fork+0x67/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/29 00:56 android16-6.12 c96ce3cae8c3 95008c03 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in fuse_flush
2026/03/28 15:05 android16-6.12 2dda9e2ebc9a b5ceaad2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in fuse_flush
* Struck through repros no longer work on HEAD.