INFO: rcu detected stall in call_usermodehelper_exec_async (4)

Status: upstream: reported C repro on 2025/11/27 14:55
Subsystems: mm
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+be81254ae29faa71cdfe@syzkaller.appspotmail.com
First crash: 497d, last: 8d01h
Cause bisection: failed (error log, bisect log)
  
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
733f030e assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ INFO: rcu detected stall in call_usermodehelper_exec_async (4) 2026/06/01 04:41 2026/06/01 04:41 2026/06/01 05:40 6b4a8443
6790da8f assessment-security 💥 INFO: rcu detected stall in call_usermodehelper_exec_async (4) 2026/05/15 10:21 2026/05/15 10:21 2026/05/15 10:22 9cd3beaa
▶ ▼ 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 (8)
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 475d 475d 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 856d 856d 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 2505d 2505d 0/29 closed as invalid on 2019/12/04 14:14
linux-6.1 INFO: rcu detected stall in call_usermodehelper_exec_async (3) 1 1 125d 125d 0/3 auto-obsoleted due to no activity on 2026/09/17 01:12
linux-5.15 INFO: rcu detected stall in call_usermodehelper_exec_async 1 1 1198d 1198d 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 605d 1101d 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 1595d 1595d 0/29 auto-closed as invalid on 2022/08/28 20:38
upstream BUG: soft lockup in call_usermodehelper_exec_async mm 1 2 1800d 1851d 0/29 closed as dup on 2021/09/17 07:37
▶ ▼ Last patch testing requests (2)
Created Duration User Patch Repo Result
2026/09/20 10:48 0m retest repro net error job log
2025/12/07 22:22 37m retest repro linux-next no crash log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5962/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=16285, q=1507 ncpus=2)
task:modprobe        state:R  running task     stack:25368 pid:5962  tgid:5962  ppid:34     task_flags:0x400000 flags:0x00080001
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5533 [inline]
 __schedule+0x17db/0x58f0 kernel/sched/core.c:7284
 preempt_schedule_irq+0x4b/0x90 kernel/sched/core.c:7606
 irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:539 [inline]
 irqentry_exit+0x14f/0x910 kernel/entry/common.c:167
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:lock_acquire+0x232/0x350 kernel/locking/lockdep.c:5947
Code: ff ff ff e8 b0 9d 43 0a f7 44 24 10 00 02 00 00 0f 84 38 ff ff ff 65 48 8b 05 42 48 f2 11 48 3b 44 24 50 75 33 fb 48 83 c4 58 <5b> 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc 48 8d 3d 87 56 da
RSP: 0018:ffffc9000346f0e0 EFLAGS: 00000292
RAX: 4674474cacde2900 RBX: 0000000000000000 RCX: 0000000000000046
RDX: 000000000a2ce7fc RSI: ffffffff8e69f4bd RDI: ffffffff8c6dad80
RBP: ffff88802eb85dc0 R08: ffffffff8177f1df R09: 0000000000000000
R10: ffffc9000346f218 R11: ffffffff81b2a310 R12: ffffffff8ed5c8a0
R13: 0000000000000002 R14: 0000000000000000 R15: 0000000000000246
 rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 rcu_read_lock include/linux/rcupdate.h:849 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1216 [inline]
 unwind_next_frame+0xac/0x2550 arch/x86/kernel/unwind_orc.c:495
 arch_stack_walk+0x11b/0x150 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:351 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:377
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4683 [inline]
 slab_alloc_node mm/slub.c:4996 [inline]
 kmem_cache_alloc_noprof+0x2b9/0x600 mm/slub.c:5010
 ptlock_alloc mm/memory.c:7721 [inline]
 ptlock_init include/linux/mm.h:3884 [inline]
 pmd_ptlock_init include/linux/mm.h:3996 [inline]
 pagetable_pmd_ctor include/linux/mm.h:4024 [inline]
 pmd_alloc_one_noprof include/asm-generic/pgalloc.h:146 [inline]
 __pmd_alloc+0xc1/0x5c0 mm/memory.c:6962
 pmd_alloc include/linux/mm.h:3710 [inline]
 __handle_mm_fault mm/memory.c:6656 [inline]
 handle_mm_fault+0xe9d/0x3750 mm/memory.c:6876
 do_user_addr_fault+0x746/0x1340 arch/x86/mm/fault.c:1394
 handle_page_fault arch/x86/mm/fault.c:1483 [inline]
 exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1536
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595
RIP: 0010:rep_stos_alternative+0x40/0x80 arch/x86/lib/clear_page_64.S:76
Code: c9 75 f6 c3 cc cc cc cc 48 89 07 48 83 c7 08 83 e9 08 74 ef 83 f9 08 73 ef eb de 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 <48> 89 07 48 89 47 08 48 89 47 10 48 89 47 18 48 89 47 20 48 89 47
RSP: 0018:ffffc9000346fa00 EFLAGS: 00050206
RAX: 0000000000000000 RBX: 0000561433cd9010 RCX: 0000000000000ff8
RDX: 00000000085da2bd RSI: ffffffff8e69f4bd RDI: 0000561433cd9008
RBP: dffffc0000000000 R08: ffffffff821ed4ef R09: 0000000000000000
R10: dffffc0000000000 R11: ffffed1005d70bb9 R12: 0000561433cd9008
R13: 0000000000000008 R14: 0000000000000ff8 R15: ffff888031db4118
 __clear_user arch/x86/include/asm/uaccess_64.h:190 [inline]
 clear_user arch/x86/include/asm/uaccess_64.h:207 [inline]
 padzero fs/binfmt_elf.c:134 [inline]
 elf_load+0x4bc/0x6a0 fs/binfmt_elf.c:433
 load_elf_binary+0x1161/0x28d0 fs/binfmt_elf.c:1188
 search_binary_handler fs/exec.c:1779 [inline]
 exec_binprm fs/exec.c:1811 [inline]
 bprm_execve+0x930/0x1590 fs/exec.c:1867
 kernel_execve+0x8c3/0x9c0 fs/exec.c:2011
 call_usermodehelper_exec_async+0x20f/0x360 kernel/umh.c:107
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: rcu_preempt kthread starved for 2980 jiffies! g16285 f0x0 RCU_GP_WAIT_FQS(5) ->state=R ->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:27496 pid:17    tgid:17    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5533 [inline]
 __schedule+0x17db/0x58f0 kernel/sched/core.c:7284
 __schedule_loop kernel/sched/core.c:7361 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7376
 schedule_timeout+0x152/0x2c0 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x30c/0x11f0 kernel/rcu/tree.c:2122
 rcu_gp_kthread+0x9e/0x2b0 kernel/rcu/tree.c:2330
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 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: 5764 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:csd_lock_wait kernel/smp.c:363 [inline]
RIP: 0010:csd_lock kernel/smp.c:396 [inline]
RIP: 0010:smp_call_function_many_cond+0x63e/0x1500 kernel/smp.c:944
Code: 07 e8 f6 53 0c 00 eb 3f f3 90 48 b8 00 00 00 00 00 fc ff df 41 0f b6 04 04 84 c0 75 0f f7 03 01 00 00 00 74 1d e8 d2 53 0c 00 <eb> dc 89 d9 80 e1 07 80 c1 03 38 c1 7c e5 48 89 df e8 cc 56 7c 00
RSP: 0018:ffffc9000369f320 EFLAGS: 00000293
RAX: ffffffff81bb9a3e RBX: ffff8880b8643708 RCX: ffff88802febbe80
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc9000369f470 R08: ffff88802febd41f R09: 1ffff11005fd7a83
R10: dffffc0000000000 R11: 0000000000000000 R12: 1ffff110170c86e1
R13: 0000000000000000 R14: ffff8880b8643700 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff888124dc7000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8b41de0e9c CR3: 00000000772a6000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __flush_tlb_multi arch/x86/include/asm/paravirt.h:46 [inline]
 flush_tlb_multi arch/x86/mm/tlb.c:1361 [inline]
 flush_tlb_mm_range+0x8ff/0x1090 arch/x86/mm/tlb.c:1435
 tlb_flush arch/x86/include/asm/tlb.h:23 [inline]
 tlb_flush_mmu_tlbonly include/asm-generic/tlb.h:509 [inline]
 tlb_flush_mmu+0x1af/0xa30 mm/mmu_gather.c:423
 tlb_finish_mmu+0xf4/0x220 mm/mmu_gather.c:549
 free_ldt_pgtables+0x192/0x360 arch/x86/kernel/ldt.c:411
 arch_exit_mmap arch/x86/include/asm/mmu_context.h:229 [inline]
 exit_mmap+0x1bf/0x9f0 mm/mmap.c:1300
 __mmput+0x118/0x420 kernel/fork.c:1193
 exit_mm+0x18e/0x240 kernel/exit.c:592
 do_exit+0x6cd/0x2360 kernel/exit.c:974
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1129
 get_signal+0x121b/0x12c0 kernel/signal.c:3112
 arch_do_signal_or_restart+0xbb/0x860 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop+0x10e/0x770 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:343 [inline]
 do_syscall_64+0x328/0x520 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f44f4d592d7
Code: Unable to access opcode bytes at 0x7f44f4d592ad.
RSP: 002b:00007ffc62735090 EFLAGS: 00000202 ORIG_RAX: 000000000000003d
RAX: fffffffffffffe00 RBX: 000055556ce62500 RCX: 00007f44f4d592d7
RDX: 0000000040000000 RSI: 00007ffc627350ec RDI: ffffffffffffffff
RBP: 00007ffc627350ec R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 00007ffc62735168
R13: 0000000000000002 R14: 00007ffc62735348 R15: 0000000000000000
 </TASK>

Crashes (19):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/04 10:40 net 6dc989ea46b9 57bbd979 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in call_usermodehelper_exec_async
2026/09/02 01:19 net 1d2929d0850f 587f6b29 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in call_usermodehelper_exec_async
2026/07/27 07:21 upstream 4235cb24ec1e 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in call_usermodehelper_exec_async
2026/07/11 15:21 upstream d96fcfe1b7f9 d78ea535 .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
2026/07/04 05:36 upstream 71dfdfb0209b fcece630 .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
2026/03/27 19:54 upstream 46b513250491 ef441708 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in call_usermodehelper_exec_async
2026/03/07 18:48 upstream 4ae12d8bd9a8 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in call_usermodehelper_exec_async
2025/11/08 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
2026/07/13 20:44 net 3f1f75536668 a870962e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in call_usermodehelper_exec_async
2026/06/23 16:19 net a986fde914d8 4b1d8f01 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in call_usermodehelper_exec_async
2026/06/07 03:51 net 9772589b57e4 cc095639 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in call_usermodehelper_exec_async
2026/05/31 00:49 net 78ef59e7a645 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in call_usermodehelper_exec_async
2025/12/31 03:21 net 1adaea51c61b d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-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.