From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-il1-f205.google.com (mail-il1-f205.google.com [209.85.166.205]) (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 784A831281E for ; Thu, 27 Nov 2025 14:55:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.166.205 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764255327; cv=none; b=sC8fD9NRjD8zDzd9ySB9AjeNGU+u4UvwO7PaOlxxwSizGNC2jQ2GiUvoVUFyGS6z7YpS0uQJ/2ZERy5JeXbPaL+Lqk8cSjwIbHuvaZXgDjrDl/qwCUd69H5eySQPzCrrPC7ggyVamY8u/QSLUAQPvbP9kV6ipEeOvSULURQl2Fg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764255327; c=relaxed/simple; bh=astQzhTI9C/hsh59wtzNs2arXWbfcbsTEJ/7GsXTzQo=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; 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List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a92:cd44:0:b0:433:68e3:7679 with SMTP id e9e14a558f8ab-435dd043b29mr76588715ab.8.1764255324606; Thu, 27 Nov 2025 06:55:24 -0800 (PST) Date: Thu, 27 Nov 2025 06:55:24 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6928665c.a70a0220.d98e3.0109.GAE@google.com> Subject: [syzbot] [udf?] INFO: rcu detected stall in call_usermodehelper_exec_async (4) From: syzbot To: brauner@kernel.org, jack@suse.com, jack@suse.cz, kees@kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: d724c6f85e80 Add linux-next specific files for 20251121 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=16f1f742580000 kernel config: https://syzkaller.appspot.com/x/.config?x=68d11c703cf8e4a0 dashboard link: https://syzkaller.appspot.com/bug?extid=be81254ae29faa71cdfe 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=12c3ea12580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1064d8b4580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/0ccfc806f65a/disk-d724c6f8.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/c2ec31ffb05e/vmlinux-d724c6f8.xz kernel image: https://storage.googleapis.com/syzbot-assets/c25d9c0c1917/bzImage-d724c6f8.xz mounted in repro: https://storage.googleapis.com/syzbot-assets/9174536af225/mount_0.gz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+be81254ae29faa71cdfe@syzkaller.appspotmail.com rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P6121/1:b..l rcu: (detected by 1, t=10502 jiffies, g=13961, q=394 ncpus=2) task:modprobe state:R running task stack:26056 pid:6121 tgid:6121 ppid:13 task_flags:0x400000 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5257 [inline] __schedule+0x14bc/0x5030 kernel/sched/core.c:6864 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7191 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:unwind_next_frame+0xaa5/0x2390 arch/x86/kernel/unwind_orc.c:581 Code: 00 49 89 df 49 c1 ef 03 41 0f b6 04 2f 84 c0 0f 85 88 13 00 00 0f b6 76 01 83 e6 07 83 fe 04 4c 89 64 24 10 0f 84 49 04 00 00 <83> fe 03 0f 84 f3 01 00 00 83 fe 02 0f 85 a1 07 00 00 4c 89 7c 24 RSP: 0018:ffffc90003287898 EFLAGS: 00000293 RAX: 0000000000000000 RBX: ffffffff900ba31f RCX: ffffffff8f90e4cc RDX: ffffffff900ba31a RSI: 0000000000000002 RDI: ffffffff8bbf8180 RBP: dffffc0000000000 R08: 0000000000000003 R09: ffffffff81745035 R10: ffffc900032879b8 R11: ffffffff81adcc20 R12: ffffc90003287f48 R13: ffffc900032879b8 R14: ffffc90003287968 R15: 1ffffffff2017463 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:56 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:77 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:252 [inline] __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:284 kasan_slab_free include/linux/kasan.h:234 [inline] slab_free_hook mm/slub.c:2540 [inline] slab_free mm/slub.c:6663 [inline] kfree+0x1c0/0x680 mm/slub.c:6871 kernel_execve+0x3c7/0x9f0 fs/exec.c:1922 call_usermodehelper_exec_async+0x210/0x360 kernel/umh.c:109 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 10537 jiffies! g13961 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0 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:27064 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5257 [inline] __schedule+0x14bc/0x5030 kernel/sched/core.c:6864 __schedule_loop kernel/sched/core.c:6946 [inline] schedule+0x165/0x360 kernel/sched/core.c:6961 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: Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 UID: 0 PID: 0 Comm: swapper/0 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: cc cc cc cc 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 33 70 0c 00 f3 0f 1e fa fb f4 c8 f2 02 00 cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 RSP: 0018:ffffffff8dc07d80 EFLAGS: 000002c6 RAX: 9d3ae734e5c61000 RBX: ffffffff8197acb7 RCX: 9d3ae734e5c61000 RDX: 0000000000000001 RSI: ffffffff8d78f71d RDI: ffffffff8bbf81e0 RBP: ffffffff8dc07ea8 R08: ffff8880b86336db R09: 1ffff110170c66db R10: dffffc0000000000 R11: ffffed10170c66dc R12: ffffffff8f7deb70 R13: 0000000000000000 R14: 0000000000000000 R15: 1ffffffff1b92a60 FS: 0000000000000000(0000) GS:ffff888125eba000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fc4b4703020 CR3: 000000002998e000 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:190 [inline] do_idle+0x1e7/0x510 kernel/sched/idle.c:330 cpu_startup_entry+0x44/0x60 kernel/sched/idle.c:428 rest_init+0x2de/0x300 init/main.c:757 start_kernel+0x3a7/0x410 init/main.c:1206 x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310 x86_64_start_kernel+0x143/0x1c0 arch/x86/kernel/head64.c:291 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