syzbot


INFO: rcu detected stall in call_usermodehelper_exec_async (4)

Status: upstream: reported C repro on 2025/11/27 14:55
Subsystems: udf
[Documentation on labels]
Reported-by: syzbot+be81254ae29faa71cdfe@syzkaller.appspotmail.com
First crash: 191d, last: 16d
Cause bisection: failed (error log, bisect log)
  
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [udf?] INFO: rcu detected stall in call_usermodehelper_exec_async (4) 0 (1) 2025/11/27 14:55
Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in call_usermodehelper_exec_async (2) 1 1 169d 169d 0/3 auto-obsoleted due to no activity on 2025/10/01 17:46
linux-6.1 INFO: rcu detected stall in call_usermodehelper_exec_async 1 1 550d 550d 0/3 auto-obsoleted due to no activity on 2024/09/16 03:00
upstream INFO: rcu detected stall in call_usermodehelper_exec_async mm 1 1 2199d 2199d 0/29 closed as invalid on 2019/12/04 14:14
linux-5.15 INFO: rcu detected stall in call_usermodehelper_exec_async 1 1 892d 892d 0/3 auto-obsoleted due to no activity on 2023/10/09 16:55
upstream INFO: rcu detected stall in call_usermodehelper_exec_async (3) mm 1 23 299d 795d 0/29 auto-obsoleted due to no activity on 2025/05/14 21:52
upstream INFO: rcu detected stall in call_usermodehelper_exec_async (2) cgroups mm 1 1 1289d 1289d 0/29 auto-closed as invalid on 2022/08/28 20:38
upstream BUG: soft lockup in call_usermodehelper_exec_async mm 1 2 1494d 1545d 0/29 closed as dup on 2021/09/17 07:37
Last patch testing requests (1)
Created Duration User Patch Repo Result
2025/12/07 22:22 37m retest repro linux-next OK log

Sample crash report:
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P19080/1:b..l P28235/1:b..l P5919/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=162785, q=830 ncpus=1)
task:kworker/1:4     state:R  running task     stack:26232 pid:5919  tgid:5919  ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: events_power_efficient gc_worker
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6929
 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7256
 irqentry_exit+0x36/0x90 kernel/entry/common.c:211
 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:688
RIP: 0010:__seqprop_spinlock_sequence include/linux/seqlock.h:227 [inline]
RIP: 0010:nf_conntrack_get_ht include/net/netfilter/nf_conntrack.h:342 [inline]
RIP: 0010:gc_worker+0x2d5/0x16e0 net/netfilter/nf_conntrack_core.c:1548
Code: 00 00 48 c7 c7 48 ee 82 90 e8 17 00 1c f8 9c 5b 81 e3 00 02 00 00 31 ff 48 89 de e8 85 0a 40 f8 58 48 85 db 0f 85 d4 0f 00 00 <e8> 06 0f 40 f8 8b 1d f0 8f 06 07 41 89 dc 31 ff 41 83 e4 01 44 89
RSP: 0018:ffffc90004a7fb48 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff897c6989
RDX: ffff8880722a8000 RSI: ffffffff897c6998 RDI: 0000000000000007
RBP: ffffffff9af7a9ec R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff88814cc00000
R13: 0000000000040000 R14: dffffc0000000000 R15: 0000000000001770
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263
 process_scheduled_works kernel/workqueue.c:3346 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
task:kworker/u11:4   state:R  running task     stack:29800 pid:28235 tgid:28235 ppid:15449  task_flags:0x8040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6929
 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7256
 irqentry_exit+0x36/0x90 kernel/entry/common.c:211
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:lockdep_enabled kernel/locking/lockdep.c:124 [inline]
RIP: 0010:lock_acquire kernel/locking/lockdep.c:5844 [inline]
RIP: 0010:lock_acquire+0x127/0x350 kernel/locking/lockdep.c:5825
Code: 0d 42 0c ea 0e 85 c9 0f 84 b1 00 00 00 65 8b 05 c7 0b 09 12 85 c0 0f 85 a2 00 00 00 65 48 8b 05 07 ca 08 12 8b 90 2c 0b 00 00 <85> d2 0f 85 8c 00 00 00 9c 8f 04 24 fa 48 c7 c7 ec 7a b1 8d e8 20
RSP: 0018:ffffc9000438f928 EFLAGS: 00000246
RAX: ffff888030cdbc80 RBX: ffffffff8e3c45e0 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffffff816bc5f1 RDI: fffffbfff1c788bc
RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000035424 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 rcu_read_lock include/linux/rcupdate.h:867 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1195 [inline]
 unwind_next_frame+0xd1/0x20a0 arch/x86/kernel/unwind_orc.c:479
 arch_stack_walk+0x94/0x100 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
 save_stack+0x160/0x1f0 mm/page_owner.c:156
 __reset_page_owner+0x84/0x1a0 mm/page_owner.c:311
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1394 [inline]
 __free_frozen_pages+0x7df/0x1160 mm/page_alloc.c:2906
 discard_slab mm/slub.c:3326 [inline]
 __put_partials+0x130/0x170 mm/slub.c:3872
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x4d/0x120 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286
 __kasan_kmalloc+0x8a/0xb0 mm/kasan/common.c:408
 kasan_kmalloc include/linux/kasan.h:262 [inline]
 __do_kmalloc_node mm/slub.c:5646 [inline]
 __kmalloc_noprof+0x32f/0x880 mm/slub.c:5658
 kmalloc_noprof include/linux/slab.h:961 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 lsm_blob_alloc+0x68/0x90 security/security.c:690
 lsm_cred_alloc security/security.c:707 [inline]
 security_prepare_creds+0x30/0x270 security/security.c:3310
 prepare_kernel_cred+0x4a8/0x750 kernel/cred.c:617
 call_usermodehelper_exec_async+0x10a/0x4c0 kernel/umh.c:88
 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
task:syz-executor    state:R  running task     stack:25912 pid:19080 tgid:19080 ppid:5818   task_flags:0x40050c flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6929
 preempt_schedule_common+0x44/0xc0 kernel/sched/core.c:7113
 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
 __raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline]
 _raw_spin_unlock+0x3e/0x50 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:391 [inline]
 zap_pte_range mm/memory.c:1884 [inline]
 zap_pmd_range mm/memory.c:1946 [inline]
 zap_pud_range mm/memory.c:1975 [inline]
 zap_p4d_range mm/memory.c:1996 [inline]
 unmap_page_range+0xf71/0x41b0 mm/memory.c:2017
 unmap_single_vma.constprop.0+0x153/0x240 mm/memory.c:2060
 unmap_vmas+0x218/0x470 mm/memory.c:2104
 exit_mmap+0x1b2/0xb90 mm/mmap.c:1280
 __mmput+0x12a/0x410 kernel/fork.c:1133
 mmput+0x62/0x70 kernel/fork.c:1156
 exit_mm kernel/exit.c:582 [inline]
 do_exit+0x7c7/0x2bf0 kernel/exit.c:954
 do_group_exit+0xd3/0x2a0 kernel/exit.c:1107
 get_signal+0x2671/0x26d0 kernel/signal.c:3034
 arch_do_signal_or_restart+0x8f/0x790 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x85/0x130 kernel/entry/common.c:40
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x426/0xfa0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff2021857d3
RSP: 002b:00007ffff9506248 EFLAGS: 00000202 ORIG_RAX: 000000000000003d
RAX: fffffffffffffe00 RBX: 0000000000004a99 RCX: 00007ff2021857d3
RDX: 0000000040000000 RSI: 00007ffff950625c RDI: 00000000ffffffff
RBP: 00007ffff950625c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000008
R13: 0000000000000003 R14: 00007ffff9506548 R15: 0000000000000000
 </TASK>
rcu: rcu_preempt kthread starved for 1036 jiffies! g162785 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:28552 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6929
 __schedule_loop kernel/sched/core.c:7011 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:7026
 schedule_timeout+0x123/0x290 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x1ea/0xaf0 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x26d/0x380 kernel/rcu/tree.c:2285
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 UID: 0 PID: 3413 Comm: kworker/R-bat_e Tainted: G     U              syzkaller #0 PREEMPT(full) 
Tainted: [U]=USER
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: bat_events batadv_tt_purge
RIP: 0010:__sanitizer_cov_trace_pc+0x66/0x70 kernel/kcov.c:235
Code: 82 58 16 00 00 83 f8 02 75 20 48 8b 8a 60 16 00 00 8b 92 5c 16 00 00 48 8b 01 48 83 c0 01 48 39 d0 73 07 48 89 01 48 89 34 c1 <c3> cc cc cc cc 0f 1f 44 00 00 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90000a07c60 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffffffff8984759a
RDX: ffff888030d38000 RSI: ffffffff8984789c RDI: 0000000000000007
RBP: ffff888162872b40 R08: 0000000000000007 R09: 0000000000000007
R10: 0000000000000000 R11: ffff888162872bf8 R12: ffffc90000a07d58
R13: 0000000000000000 R14: ffffffff898474d0 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff888124b0d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055947acf8088 CR3: 00000000798e2000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 nf_nat_ipv6_out net/netfilter/nf_nat_proto.c:999 [inline]
 nf_nat_ipv6_out+0x3cc/0x4c0 net/netfilter/nf_nat_proto.c:972
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0xbe/0x200 net/netfilter/core.c:623
 nf_hook+0x471/0x7a0 include/linux/netfilter.h:273
 NF_HOOK include/linux/netfilter.h:316 [inline]
 br_nf_post_routing+0x8bd/0x1190 net/bridge/br_netfilter_hooks.c:966
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0xbe/0x200 net/netfilter/core.c:623
 nf_hook+0x45e/0x780 include/linux/netfilter.h:273
 NF_HOOK include/linux/netfilter.h:316 [inline]
 br_forward_finish+0xcd/0x130 net/bridge/br_forward.c:66
 br_nf_hook_thresh+0x307/0x410 net/bridge/br_netfilter_hooks.c:1167
 br_nf_forward_finish+0x66a/0xba0 net/bridge/br_netfilter_hooks.c:662
 NF_HOOK include/linux/netfilter.h:318 [inline]
 NF_HOOK include/linux/netfilter.h:312 [inline]
 br_nf_forward_ip.part.0+0x609/0x810 net/bridge/br_netfilter_hooks.c:716
 br_nf_forward_ip net/bridge/br_netfilter_hooks.c:676 [inline]
 br_nf_forward+0xf0f/0x1be0 net/bridge/br_netfilter_hooks.c:773
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0xbe/0x200 net/netfilter/core.c:623
 nf_hook+0x45e/0x780 include/linux/netfilter.h:273
 NF_HOOK include/linux/netfilter.h:316 [inline]
 __br_forward+0x1be/0x5b0 net/bridge/br_forward.c:115
 deliver_clone net/bridge/br_forward.c:131 [inline]
 maybe_deliver+0xf1/0x180 net/bridge/br_forward.c:191
 br_flood+0x17c/0x650 net/bridge/br_forward.c:238
 br_handle_frame_finish+0x1117/0x1f00 net/bridge/br_input.c:229
 br_nf_hook_thresh+0x307/0x410 net/bridge/br_netfilter_hooks.c:1167
 br_nf_pre_routing_finish_ipv6+0x76a/0xfc0 net/bridge/br_netfilter_ipv6.c:154
 NF_HOOK include/linux/netfilter.h:318 [inline]
 br_nf_pre_routing_ipv6+0x3cd/0x8c0 net/bridge/br_netfilter_ipv6.c:184
 br_nf_pre_routing+0x860/0x15b0 net/bridge/br_netfilter_hooks.c:508
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:291 [inline]
 br_handle_frame+0xb28/0x14e0 net/bridge/br_input.c:442
 __netif_receive_skb_core.constprop.0+0xa25/0x4bd0 net/core/dev.c:5966
 __netif_receive_skb_one_core+0xb0/0x1e0 net/core/dev.c:6077
 __netif_receive_skb+0x1d/0x160 net/core/dev.c:6192
 process_backlog+0x439/0x15e0 net/core/dev.c:6544
 __napi_poll.constprop.0+0xba/0x550 net/core/dev.c:7594
 napi_poll net/core/dev.c:7657 [inline]
 net_rx_action+0x97f/0xef0 net/core/dev.c:7784
 handle_softirqs+0x219/0x8e0 kernel/softirq.c:622
 do_softirq kernel/softirq.c:523 [inline]
 do_softirq+0xb2/0xf0 kernel/softirq.c:510
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x100/0x120 kernel/softirq.c:450
 spin_unlock_bh include/linux/spinlock.h:396 [inline]
 batadv_tt_global_purge net/batman-adv/translation-table.c:2250 [inline]
 batadv_tt_purge+0x25f/0xb80 net/batman-adv/translation-table.c:3510
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263
 process_scheduled_works kernel/workqueue.c:3346 [inline]
 rescuer_thread+0x620/0xea0 kernel/workqueue.c:3523
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
net_ratelimit: 4366 callbacks suppressed
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:f2:49:8b:d8:19:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:f2:49:8b:d8:19:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
net_ratelimit: 6583 callbacks suppressed
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:f2:49:8b:d8:19:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:f2:49:8b:d8:19:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:f2:49:8b:d8:19:1b, vlan:0)

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/08 20:08 upstream e811c33b1f13 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in call_usermodehelper_exec_async
2025/10/30 20:52 upstream e53642b87a4f fd2207e7 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in call_usermodehelper_exec_async
2025/08/19 15:22 upstream be48bcf004f9 523f460e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in call_usermodehelper_exec_async
2025/07/19 17:01 upstream 4871b7cb27f4 7117feec .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in call_usermodehelper_exec_async
2025/07/11 04:54 upstream bc9ff192a6c9 3cda49cf .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in call_usermodehelper_exec_async
2025/06/01 16:48 upstream 7d4e49a77d99 3d2f584d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in call_usermodehelper_exec_async
2025/11/23 14:41 linux-next d724c6f85e80 4fb8ef37 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci-upstream-linux-next-kasan-gce-root INFO: rcu detected stall in call_usermodehelper_exec_async
* Struck through repros no longer work on HEAD.