From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ot1-f80.google.com (mail-ot1-f80.google.com [209.85.210.80]) (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 6823C199230 for ; Mon, 22 Dec 2025 03:48:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.80 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766375311; cv=none; b=gxI35y399OnJO18Vswuzzk6pMrZSx9UEmIXMRL2amkG9vemf6tUC6EDqU9AjkRCjgVp4kL/LJhYhKlX67Hi1WME2foAzdc2Bk+5PnmvYHGgu4Ps3/WbPJTJ4fqW2XyGk8/HMb/DJNXz5M+VOvS0p4iJcQZk4kE1n5yi6fpYZ8ZU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766375311; c=relaxed/simple; bh=KVaKQ81mbJBXdvk/UbvYDDz7h7cMKud+nTsj1J6ekCE=; 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:a05:6820:330d:b0:65d:762:749a with SMTP id 006d021491bc7-65d0e94d689mr3139229eaf.7.1766375308236; Sun, 21 Dec 2025 19:48:28 -0800 (PST) Date: Sun, 21 Dec 2025 19:48:28 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6948bf8c.050a0220.1b4e0c.0030.GAE@google.com> Subject: [syzbot] [tomoyo?] [mm?] INFO: rcu detected stall in sys_newfstat (4) From: syzbot To: jmorris@namei.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, paul@paul-moore.com, penguin-kernel@I-love.SAKURA.ne.jp, serge@hallyn.com, syzkaller-bugs@googlegroups.com, takedakn@nttdata.co.jp, tomoyo-users_en@lists.sourceforge.net Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 12b95d29eb97 Add linux-next specific files for 20251217 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=16bbd31a580000 kernel config: https://syzkaller.appspot.com/x/.config?x=9b53f0e28d100777 dashboard link: https://syzkaller.appspot.com/bug?extid=5fb7dcd004f42cb418d7 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=11355d92580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/0264b4454f47/disk-12b95d29.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/72a383625b53/vmlinux-12b95d29.xz kernel image: https://storage.googleapis.com/syzbot-assets/6499b25d444f/bzImage-12b95d29.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+5fb7dcd004f42cb418d7@syzkaller.appspotmail.com rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P5966/1:b..l rcu: (detected by 0, t=10502 jiffies, g=13749, q=681 ncpus=2) task:udevd state:R running task stack:24376 pid:5966 tgid:5966 ppid:5200 task_flags:0x400140 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5258 [inline] __schedule+0x150e/0x5070 kernel/sched/core.c:6866 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7193 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:lock_acquire+0x16c/0x340 kernel/locking/lockdep.c:5872 Code: 00 00 00 00 9c 8f 44 24 30 f7 44 24 30 00 02 00 00 0f 85 cd 00 00 00 f7 44 24 08 00 02 00 00 74 01 fb 65 48 8b 05 74 3f 25 11 <48> 3b 44 24 58 0f 85 e5 00 00 00 48 83 c4 60 5b 41 5c 41 5d 41 5e RSP: 0018:ffffc900035174d8 EFLAGS: 00000206 RAX: 550ae36b7d32a800 RBX: 0000000000000000 RCX: 550ae36b7d32a800 RDX: 0000000002aa642d RSI: ffffffff8dc9133e RDI: ffffffff8be243e0 RBP: ffffffff81746f85 R08: ffffffff81746f85 R09: ffffffff8e33f8a0 R10: ffffc90003517698 R11: ffffffff81addf20 R12: 0000000000000002 R13: ffffffff8e33f8a0 R14: 0000000000000000 R15: 0000000000000246 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+0xc2/0x23d0 arch/x86/kernel/unwind_orc.c:495 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:6674 [inline] kfree+0x1c0/0x660 mm/slub.c:6882 tomoyo_realpath_from_path+0x598/0x5d0 security/tomoyo/realpath.c:286 tomoyo_get_realpath security/tomoyo/file.c:151 [inline] tomoyo_path_perm+0x213/0x4b0 security/tomoyo/file.c:822 security_inode_getattr+0x12f/0x330 security/security.c:1869 vfs_getattr fs/stat.c:259 [inline] vfs_fstat fs/stat.c:281 [inline] __do_sys_newfstat fs/stat.c:555 [inline] __se_sys_newfstat fs/stat.c:550 [inline] __x64_sys_newfstat+0xfc/0x200 fs/stat.c:550 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fcf92911ad7 RSP: 002b:00007ffe4ab44048 EFLAGS: 00000246 ORIG_RAX: 0000000000000005 RAX: ffffffffffffffda RBX: 00005558e4439050 RCX: 00007fcf92911ad7 RDX: 0000000000000000 RSI: 00007ffe4ab44090 RDI: 0000000000000009 RBP: 0000000000000001 R08: 0000000000000620 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00005558ba62e95f R13: 00005558ba63f660 R14: 0000000000000000 R15: 0000000000000009 rcu: rcu_preempt kthread starved for 10446 jiffies! g13749 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:27728 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5258 [inline] __schedule+0x150e/0x5070 kernel/sched/core.c:6866 __schedule_loop kernel/sched/core.c:6948 [inline] schedule+0x165/0x360 kernel/sched/core.c:6963 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: 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 be 21 00 f3 0f 1e fa fb f4 48 ee 02 00 cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 RSP: 0018:ffffffff8e007d80 EFLAGS: 000002c6 RAX: da29ab50f81b1900 RBX: ffffffff8197c88a RCX: da29ab50f81b1900 RDX: 0000000000000001 RSI: ffffffff8daa76bd RDI: ffffffff8be243e0 RBP: ffffffff8e007ea8 R08: ffff8880b86336db R09: 1ffff110170c66db R10: dffffc0000000000 R11: ffffed10170c66dc R12: ffffffff8fc3b070 R13: 1ffffffff1c129b8 R14: 0000000000000000 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8881259e1000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b31163fff CR3: 0000000077280000 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 rest_init+0x2de/0x300 init/main.c:757 start_kernel+0x3a7/0x400 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