From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oo1-f79.google.com (mail-oo1-f79.google.com [209.85.161.79]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7DE352571C5 for ; Tue, 13 Jan 2026 16:49:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.79 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768322975; cv=none; b=PTEEL3UPECPi/AndKvyABRr+WZL2GRgcDo6VfdWl9NyvHkQZib1t6x0SiVYIz+d5c0oDtI5da3z5uPoKnTsfwSTWjCNL/TROhCprpsnII/7UfP/E4gxZjyPsTZsCfz+Z85Ozi0pZ5hgRv9Qk+jMagmDcOvxjOBCYfzOibOpUtrE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768322975; c=relaxed/simple; bh=JKV6GmAoHH6oMG9RtZl5ikrn+qQp/xRkZ93O5+SeUjA=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; 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List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:a1a5:b0:65f:6df9:215f with SMTP id 006d021491bc7-65f6df92832mr3738213eaf.32.1768322972506; Tue, 13 Jan 2026 08:49:32 -0800 (PST) Date: Tue, 13 Jan 2026 08:49:32 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6966779c.050a0220.1a12f3.09f0.GAE@google.com> Subject: [syzbot] [kernfs?] INFO: rcu detected stall in cleanup_net (8) From: syzbot To: davem@davemloft.net, dsahern@kernel.org, edumazet@google.com, gregkh@linuxfoundation.org, horms@kernel.org, kuba@kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, syzkaller-bugs@googlegroups.com, tj@kernel.org Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 008d3547aae5 Add linux-next specific files for 20251210 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=147c3a1a580000 kernel config: https://syzkaller.appspot.com/x/.config?x=a94030c847137a18 dashboard link: https://syzkaller.appspot.com/bug?extid=0604401cc084920f6c3d compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13f9deb4580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1406b992580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/f5497242418d/disk-008d3547.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/46fd6edd4284/vmlinux-008d3547.xz kernel image: https://storage.googleapis.com/syzbot-assets/61e6e2e573e8/bzImage-008d3547.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+0604401cc084920f6c3d@syzkaller.appspotmail.com rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P5930/1:b..l rcu: (detected by 1, t=10502 jiffies, g=11645, q=51 ncpus=2) task:kworker/u8:12 state:R running task stack:22432 pid:5930 tgid:5930 ppid:2 task_flags:0x4208060 flags:0x00080000 Workqueue: netns cleanup_net Call Trace: context_switch kernel/sched/core.c:5256 [inline] __schedule+0x14bc/0x5000 kernel/sched/core.c:6863 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7190 irqentry_exit+0x5d8/0x660 kernel/entry/common.c:216 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 RIP: 0010:rcu_is_watching+0x67/0xb0 kernel/rcu/tree.c:752 Code: 89 f7 e8 0c 71 80 00 48 c7 c3 d8 f6 7f 92 49 03 1e 48 89 d8 48 c1 e8 03 42 0f b6 04 38 84 c0 75 34 8b 03 65 ff 0d 79 1d d7 10 <74> 11 83 e0 04 c1 e8 02 5b 41 5e 41 5f e9 97 d8 b6 09 cc e8 71 d5 RSP: 0018:ffffc900043af018 EFLAGS: 00000286 RAX: 000000000003f46c RBX: ffff8880b86336d8 RCX: 1e5222b0fc0eb100 RDX: 000000005b9ddbdf RSI: ffffffff8bc07c40 RDI: ffffffff8bc07c00 RBP: dffffc0000000000 R08: ffffffff81743f85 R09: ffffffff8df41a60 R10: ffffc900043af158 R11: ffffffff81ada810 R12: 1ffff92000875e21 R13: ffffc900043af140 R14: ffffffff8d9b1dd0 R15: dffffc0000000000 rcu_read_lock include/linux/rcupdate.h:868 [inline] class_rcu_constructor include/linux/rcupdate.h:1195 [inline] unwind_next_frame+0xd4/0x2390 arch/x86/kernel/unwind_orc.c:479 arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122 kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 [inline] __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2540 [inline] slab_free mm/slub.c:6668 [inline] kfree+0x1c0/0x660 mm/slub.c:6876 devinet_sysctl_unregister net/ipv4/devinet.c:2729 [inline] inetdev_destroy net/ipv4/devinet.c:334 [inline] inetdev_event+0x78e/0x15b0 net/ipv4/devinet.c:1655 notifier_call_chain+0x19d/0x3a0 kernel/notifier.c:85 call_netdevice_notifiers_extack net/core/dev.c:2269 [inline] call_netdevice_notifiers net/core/dev.c:2283 [inline] unregister_netdevice_many_notify+0x1867/0x2340 net/core/dev.c:12400 unregister_netdevice_many net/core/dev.c:12463 [inline] default_device_exit_batch+0x964/0x9e0 net/core/dev.c:13055 ops_exit_list net/core/net_namespace.c:205 [inline] ops_undo_list+0x525/0x990 net/core/net_namespace.c:252 cleanup_net+0x4d8/0x7a0 net/core/net_namespace.c:696 process_one_work+0x93a/0x15a0 kernel/workqueue.c:3279 process_scheduled_works kernel/workqueue.c:3362 [inline] worker_thread+0x9b0/0xee0 kernel/workqueue.c:3443 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 rcu: rcu_preempt kthread starved for 10553 jiffies! g11645 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:27736 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5256 [inline] __schedule+0x14bc/0x5000 kernel/sched/core.c:6863 __schedule_loop kernel/sched/core.c:6945 [inline] schedule+0x165/0x360 kernel/sched/core.c:6960 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 rcu: Stack dump where RCU GP kthread last ran: CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:82 Code: 13 ee 02 00 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 73 c0 0c 00 f3 0f 1e fa fb f4 cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 RSP: 0018:ffffc90000197de0 EFLAGS: 000002c6 RAX: 2bdaeed9ae4cb000 RBX: ffffffff8197971a RCX: 2bdaeed9ae4cb000 RDX: 0000000000000001 RSI: ffffffff8d791c9e RDI: ffffffff8bc07c60 RBP: ffffc90000197f10 R08: ffff8880b87336db R09: 1ffff110170e66db R10: dffffc0000000000 R11: ffffed10170e66dc R12: ffffffff8f820770 R13: 1ffff110039dcb70 R14: 0000000000000001 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff888125f34000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffee7189228 CR3: 00000000753b0000 CR4: 00000000003526f0 Call Trace: arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline] default_idle+0x13/0x20 arch/x86/kernel/process.c:767 default_idle_call+0x73/0xb0 kernel/sched/idle.c:122 cpuidle_idle_call kernel/sched/idle.c:191 [inline] do_idle+0x1ea/0x520 kernel/sched/idle.c:332 cpu_startup_entry+0x44/0x60 kernel/sched/idle.c:430 start_secondary+0x101/0x110 arch/x86/kernel/smpboot.c:312 common_startup_64+0x13e/0x147 --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing. If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup