From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oo1-f72.google.com (mail-oo1-f72.google.com [209.85.161.72]) (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 056D438B14C for ; Wed, 2 Sep 2026 22:31:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.72 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788388300; cv=none; b=EDQjjL2avxkFak9pBrdEo9fPd7IsR0AMCTDC1iL31PbMLtUi0tr14ZLyP2L7deRtDmoC0y5ijeopM3cihWyxqsWNsQq3Zp3v1AZukseOvYZrTMzRpCaIEtNO847KOnnFndQWz+G6mxqXO0jkV3z4PnVAC2ASR3uBet76alGbL7w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788388300; c=relaxed/simple; bh=NLAws/3aTtmyrmhPm11IDzKhJlV7oE0jZENDzlOr84U=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=QZj1FytEhDmSL35S/+XHige0KxNjVkBONH0kliBLauaQ8meAd6bgeAz1dsMlAaOcW2P/0/lpZRiFbjExUhi5V1uLv062vYKxh+PA9CVCJuKIqm8oc0Z5IXICYBf1pP6wvmOYtAWjkItW7tAqSICspNnkjMe21PZfOMf487opYfQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.161.72 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oo1-f72.google.com with SMTP id 006d021491bc7-6b173742296so438224eaf.0 for ; Wed, 02 Sep 2026 15:31:36 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1788388293; x=1788993093; h=content-type:to:from:subject:message-id:in-reply-to:date :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to:content-type; bh=W+pl83gb4I7QNRSCAXRvNHTTFXcGygtvzShFK/lpDNA=; b=BCmEEW+TlbjWOfc2bgbdKowPkYeDBJiK++/PDsmVUtoOvNDlNE52PbTAfvD3g2ZuH0 5p4yjNLr1m/oFwHrNrrxox7mr3JZw0HOAFHJonnm29GhSYbp3ASXytNJ9Sk1XqTsJrs/ Vkz/V6W6FR5UPwyhtGtILz/suAgxPqtWaCorW74Sxy3TbOrIU7DfDT2Lulm2XgDTro0l C5x2ZnJaUwOdDmBpHJV2bpsC4Ga8sbP+lffl2T0vQMKVfV/NIqIPi1GvnAlA6oq6iF4N wsZYRQSG6tinq0wvlhMNWaCzQZXS4YfD17EkcBBCwuzwuV4u2fHkolHjvUxWSHjcxGss +Tqg== X-Forwarded-Encrypted: i=1; AKwUvBxtb9hJ8bx4v63jxa32Xb+qGhCP8zgxvEEnDxjktgJy7t1a1ReyvRsA90mghm2USwcctchZlQtiwhWKcIo=@vger.kernel.org X-Gm-Message-State: AFuF++kz6CCiKALbSTRxs8TnWsmyfR6sHNfsz0qom4sZBMJonXNhcvuk GSPeFN54YZmqmF6aztBYPFV/pSAYFM20xLdT5Ipa4zNeWMKj9nipG/s72r9rRwqFfjEMYMsAA0Q d8QGvPYUdlb0WlA2YMe9wEP1f/nNPJcQRwUfnaVm9/1+3JQV3c38385a1soI= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:61d:b0:6b1:9b72:213c with SMTP id 006d021491bc7-6b582a61f27mr1555358eaf.3.1788388293215; Wed, 02 Sep 2026 15:31:33 -0700 (PDT) Date: Wed, 02 Sep 2026 15:31:33 -0700 In-Reply-To: <6a90c2f3.4d659fcc.734b4.0017.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a98a3c5.27a413cd.1e878c.0010.GAE@google.com> Subject: Re: [syzbot] [nfs?] INFO: task hung in nfsd_nrthreads From: syzbot To: cel@kernel.org, dai.ngo@oracle.com, jlayton@kernel.org, linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, neil@brown.name, okorniev@redhat.com, syzkaller-bugs@googlegroups.com, tom@talpey.com Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: 89a312991dc6 Merge tag 'cifs-fixes-7.3-rc2' of https://git.. git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git console output: https://syzkaller.appspot.com/x/log.txt?x=14c74125580000 kernel config: https://syzkaller.appspot.com/x/.config?x=8c5c3949d762a91f dashboard link: https://syzkaller.appspot.com/bug?extid=86a9d43d89b86def6d59 compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=143c8b49580000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+86a9d43d89b86def6d59@syzkaller.appspotmail.com INFO: task syz-executor195:6046 blocked for more than 10 seconds. Not tainted syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor195 state:D stack:27704 pid:6046 tgid:6041 ppid:6040 task_flags:0x400040 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5520 [inline] __schedule+0x1259/0x6920 kernel/sched/core.c:7270 __schedule_loop kernel/sched/core.c:7347 [inline] schedule+0xdd/0x2c0 kernel/sched/core.c:7362 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7419 __mutex_lock_common kernel/locking/mutex.c:726 [inline] __mutex_lock+0xccb/0x1bd0 kernel/locking/mutex.c:821 nfsd_nrthreads+0x57/0xd0 fs/nfsd/nfssvc.c:252 write_threads+0x34a/0x600 fs/nfsd/nfsctl.c:445 nfsctl_transaction_write+0x106/0x1a0 fs/nfsd/nfsctl.c:114 vfs_write+0x2aa/0x1050 fs/read_write.c:685 ksys_write+0x12a/0x250 fs/read_write.c:739 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f39e2b76239 RSP: 002b:00007f39e2341208 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00007f39e2b76239 RDX: 0000000000000000 RSI: 00007f39e2be928b RDI: 0000000000000005 RBP: 0000000000000021 R08: 0000000000000000 R09: 00007f39e2341cdc R10: 0000000000000000 R11: 0000000000000246 R12: ffffffffffffffd0 R13: 0000000000000000 R14: 00007ffe7fef6410 R15: 00007ffe7fef64f8 Showing all locks held in the system: locks held by pr/ttyS0/16: 2, last CPU#2: #0: ffffffff8edd8338 (console_srcu){....}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:314 [inline] #0: ffffffff8edd8338 (console_srcu){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:439 [inline] #0: ffffffff8edd8338 (console_srcu){....}-{0:0}, at: console_srcu_read_lock+0x49/0x60 kernel/printk/printk.c:291 #1: ffffffff9bc63c78 (&port_lock_key){-.-.}-{3:3}, at: __uart_port_lock_irqsave include/linux/serial_core.h:613 [inline] #1: ffffffff9bc63c78 (&port_lock_key){-.-.}-{3:3}, at: univ8250_console_device_lock+0x64/0xc0 drivers/tty/serial/8250/8250_core.c:413 locks held by khungtaskd/44: 1, last CPU#1: #0: ffffffff8edec060 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #0: ffffffff8edec060 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #0: ffffffff8edec060 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6837 locks held by kworker/u33:5/140: 5, last CPU#0: #0: ffff88801c0e4140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1466/0x1b10 kernel/workqueue.c:3371 #1: ffffc900028f7d08 ((work_completion)(&(&kfence_timer)->work)){+.+.}-{0:0}, at: process_one_work+0xa2c/0x1b10 kernel/workqueue.c:3372 #2: ffffffff8ec7ca50 (cpu_hotplug_lock){++++}-{0:0}, at: static_key_disable+0x12/0x20 kernel/jump_label.c:247 #3: ffffffff8ef40280 (jump_label_mutex){+.+.}-{4:4}, at: jump_label_lock kernel/jump_label.c:27 [inline] #3: ffffffff8ef40280 (jump_label_mutex){+.+.}-{4:4}, at: static_key_disable_cpuslocked+0x110/0x1c0 kernel/jump_label.c:238 #4: ffffffff8ec9c340 (text_mutex){+.+.}-{4:4}, at: arch_jump_label_transform_apply+0x17/0x30 arch/x86/kernel/jump_label.c:145 locks held by getty/5533: 2, on CPU#2: #0: ffff88802b7970a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243 #1: ffffc9000337e2e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x419/0x14e0 drivers/tty/n_tty.c:2211 locks held by syz-executor195/6044: 4, on CPU#3: #0: ffff888026dccef0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259 #1: ffff8880264cc460 (sb_writers#13){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:739 #2: ffffffff8f287680 (nfsd_mutex){+.+.}-{4:4}, at: write_ports+0xa5/0xcc0 fs/nfsd/nfsctl.c:867 #3: ffffffff90fbb440 (rpcb_create_local_mutex){+.+.}-{4:4}, at: rpcb_create_local+0x100/0x270 net/sunrpc/rpcb_clnt.c:353 locks held by syz-executor195/6046: 3, on CPU#0: #0: ffff88803d290d30 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259 #1: ffff8880264cc460 (sb_writers#13){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:739 #2: ffffffff8f287680 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nrthreads+0x57/0xd0 fs/nfsd/nfssvc.c:252 ============================================= NMI backtrace for cpu 1 CPU: 1 UID: 0 PID: 44 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 nmi_cpu_backtrace.cold+0x12d/0x151 lib/nmi_backtrace.c:123 nmi_trigger_cpumask_backtrace+0x21f/0x2a0 lib/nmi_backtrace.c:66 trigger_all_cpu_backtrace include/linux/nmi.h:164 [inline] __sys_info lib/sys_info.c:157 [inline] sys_info+0x141/0x190 lib/sys_info.c:165 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline] watchdog+0xcb1/0x1030 kernel/hung_task.c:561 kthread+0x373/0x450 kernel/kthread.c:436 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 Sending NMI from CPU 1 to CPUs 0,2-3: NMI backtrace for cpu 0 CPU: 0 UID: 0 PID: 140 Comm: kworker/u33:5 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Workqueue: events_unbound toggle_allocation_gate RIP: 0010:csd_lock_wait kernel/smp.c:363 [inline] RIP: 0010:smp_call_function_many_cond+0x8f0/0x18c0 kernel/smp.c:1002 Code: 48 b8 00 00 00 00 00 fc ff df 48 8b 4c 24 08 49 89 ce 83 e1 07 49 c1 ee 03 49 89 cd 49 01 c6 41 83 c5 03 e8 b2 bf 0c 00 f3 90 <41> 0f b6 06 41 38 c5 7c 08 84 c0 0f 85 ca 0d 00 00 8b 45 08 31 ff RSP: 0018:ffffc900028f78a0 EFLAGS: 00000293 RAX: 0000000000000000 RBX: 0000000000000002 RCX: 0000000000000000 RDX: ffff8880257c8000 RSI: ffffffff81ff305e RDI: ffff8880257c8000 RBP: ffff88806a641900 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: ffffed1004af92b3 R13: 0000000000000003 R14: ffffed100d4c8321 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff8880d5b61000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fe4bdf736e8 CR3: 000000000eb96000 CR4: 0000000000352ef0 Call Trace: on_each_cpu include/linux/smp.h:71 [inline] smp_text_poke_sync_each_cpu arch/x86/kernel/alternative.c:2602 [inline] smp_text_poke_batch_finish+0x337/0xc60 arch/x86/kernel/alternative.c:2812 arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146 jump_label_update+0x37a/0x550 kernel/jump_label.c:910 static_key_disable_cpuslocked+0x162/0x1c0 kernel/jump_label.c:240 static_key_disable+0x1a/0x20 kernel/jump_label.c:248 toggle_allocation_gate mm/kfence/core.c:909 [inline] toggle_allocation_gate+0x149/0x2d0 mm/kfence/core.c:894 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396 process_scheduled_works kernel/workqueue.c:3479 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560 kthread+0x373/0x450 kernel/kthread.c:436 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 NMI backtrace for cpu 3 CPU: 3 UID: 0 PID: 0 Comm: swapper/3 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:64 Code: 28 9c 02 e9 c3 4f 03 00 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa eb 07 0f 00 2d c3 56 1c 00 fb f4 cc cc cc cc 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90 RSP: 0018:ffffc900001a7e00 EFLAGS: 00000202 RAX: 00000000000486e5 RBX: ffff88801f698000 RCX: ffffffff8bcf6115 RDX: 0000000000000001 RSI: ffffffff8e3eb021 RDI: ffffffff8c620e80 RBP: ffffed1003ed3000 R08: 0000000000000001 R09: ffffed100d4e67bd R10: ffff88806a733deb R11: 0000000000000001 R12: 0000000000000000 R13: 0000000000000000 R14: 1ffff92000034fc4 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff8880d5e61000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055dbdf281fa0 CR3: 00000000374a8000 CR4: 0000000000352ef0 Call Trace: arch_safe_halt arch/x86/include/asm/paravirt.h:62 [inline] default_idle+0x9/0x10 arch/x86/kernel/process.c:768 default_idle_call+0x6c/0xb0 kernel/sched/idle.c:122 cpuidle_idle_call kernel/sched/idle.c:199 [inline] do_idle+0x3ae/0x5b0 kernel/sched/idle.c:355 cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:454 start_secondary+0x21d/0x2d0 arch/x86/kernel/smpboot.c:312 common_startup_64+0x13e/0x158 NMI backtrace for cpu 2 CPU: 2 UID: 0 PID: 16 Comm: pr/ttyS0 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:io_serial_out+0x8f/0xb0 drivers/tty/serial/8250/8250_port.c:416 Code: 48 8d 7d 40 44 89 e1 48 b8 00 00 00 00 00 fc ff df 48 89 fa d3 e3 48 c1 ea 03 80 3c 02 00 75 1c 66 03 5d 40 44 89 e8 89 da ee <5b> 5d 41 5c 41 5d e9 16 ae 22 06 e8 01 1b cf fc eb a0 e8 8a 1b cf RSP: 0018:ffffc900001379e0 EFLAGS: 00000002 RAX: 000000000000000d RBX: 00000000000003f8 RCX: 0000000000000000 RDX: 00000000000003f8 RSI: ffffffff85afe815 RDI: ffffffff9bc63ca0 RBP: ffffffff9bc63c60 R08: 0000000000000001 R09: 000000000000001f R10: 0000000000000000 R11: 6220363430363a49 R12: 0000000000000000 R13: 000000000000000d R14: 0000000000000008 R15: ffffc90000137da8 FS: 0000000000000000(0000) GS:ffff8880d5d61000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fe4bdf736e8 CR3: 000000002b9dc000 CR4: 0000000000352ef0 Call Trace: serial_port_out include/linux/serial_core.h:817 [inline] serial8250_console_putchar drivers/tty/serial/8250/8250_port.c:3287 [inline] __serial8250_console_fifo_write+0x20f/0x290 drivers/tty/serial/8250/8250_port.c:3356 serial8250_console_fifo_write drivers/tty/serial/8250/8250_port.c:3378 [inline] __serial8250_console_write drivers/tty/serial/8250/8250_port.c:3429 [inline] serial8250_console_write+0xf46/0x1330 drivers/tty/serial/8250/8250_port.c:3493 nbcon_emit_next_record+0x8f7/0xa70 kernel/printk/nbcon.c:1070 nbcon_emit_one+0x1a8/0x2b0 kernel/printk/nbcon.c:1157 nbcon_kthread_func+0x613/0x7d0 kernel/printk/nbcon.c:1271 kthread+0x373/0x450 kernel/kthread.c:436 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 --- 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.