From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oa1-f77.google.com (mail-oa1-f77.google.com [209.85.160.77]) (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 9A50A1EB19B for ; Sun, 16 Aug 2026 15:09:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.77 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786892979; cv=none; b=F23QqLPcSGWQC09uUPdh+ytTZPHJGuMEK0ykPj7blnd0dPOL10xVDBZ31GbN+i9JuFyyKsWVVmw9LGJeMheAN69CJ2RVB5qE3QGL4GCGsTP4AQpZliT9VuzEdDTed1CGC4gxanhb1ZbBB0vQY44JiMXHcW3em6tvSxKadXTMklw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786892979; c=relaxed/simple; bh=JlCT7Tjz2b9m7+URJCo3zLEgfl+7Y78A4svG4WZIAis=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=eiuPnD6YppiwIIHcsTv6H/rdcOb+y9hAiJXobil6JUfF2dUNScqmL7lqpibWqK5lttgC86+5yxIBdgXyfDBO4cIjNNWyfWulHKo8KiZ9Hw/YWqZP65mpOMu1Evy/gtHxyVY/+LQvvhjsN9mtN3txXOdmOnpAfIbTcoyGpKNOBdA= 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=209.85.160.77 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-oa1-f77.google.com with SMTP id 586e51a60fabf-456ae656699so3205593fac.0 for ; Sun, 16 Aug 2026 08:09:37 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786892976; x=1787497776; 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=UrfefYR3alXM+nZyPeL2keqEf+3xxZ4A+CBJes0IpY0=; b=UAkLtVVh7d4jKBQa54ImSWuwtHdzfMwgH+Ukv6FIwIedU0puO9TNnMe6JAWoyQD5sC X6djUsGcrxrAMgUJzM29FgIyvpY9btvtMJ6ULWoHcZs1YlyMLyjW/OmHKk0FuwuzgttN ftN28w5rMMsT6GtB/U+OG28UdkXBS8+uUsc7Qb2ecaRLrq+RtidooJsh9zSSKzFEANVN K+P6aWSQc3+339mQw0qhv9uxSuQxD73zD0kR8pab/5Ch5fTRENRB2ZQ4Vzoml3lAWrJj H5cJDsmUrKBGdvmfb2pKMCc0H9oMtNgjJaeoxo5RzwijIQ8ezGYvNzNkHpu6GgMVyAtp 85eg== X-Forwarded-Encrypted: i=1; AHgh+Roee5d2b17I14UQjVglPz+uKohL74AnFDF+c261Y4sOtMx4x98blUFTR8JowdH3n0vheKibmLReEWqJ6AI=@vger.kernel.org X-Gm-Message-State: AOJu0YxIj/hmGYCrKJ+KfkG7JwIkOKAPNnPjF2xp3AEKvG3yHE0PHxcQ JxYvGIthbG3UXWn3Mp/cAtPMJDSdAMXzDGG5T8kNb8kKlxtKP2AqRWpHL2RcOqaLJq1yIoQyeGZ C0ZnX/r+rKKWsdBrZr9jCvIdYwJJ/UWnK4bPtnJ+X1RtzucRblpcHm6VKbTU= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:3447:b0:4af:88b7:94a5 with SMTP id 5614622812f47-4b2412b0729mr16974943b6e.5.1786892976599; Sun, 16 Aug 2026 08:09:36 -0700 (PDT) Date: Sun, 16 Aug 2026 08:09:36 -0700 In-Reply-To: <68b016f0.a00a0220.1337b0.0004.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a81d2b0.dbb3a75c.20434b.0035.GAE@google.com> Subject: Re: [syzbot] [block?] INFO: task hung in queue_limits_commit_update_frozen From: syzbot To: axboe@kernel.dk, hch@lst.de, josef@toxicpanda.com, krystianmkaniewski@gmail.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, nbd@other.debian.org, netdev@vger.kernel.org, syzbot@kernel.org, syzbot@lists.linux.dev, syzkaller-bugs@googlegroups.com, syzkaller-upstream-moderation@googlegroups.com Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: e6a5d573d24c net: dsa: drop explicit NULL comparisons git tree: net-next console+strace: https://syzkaller.appspot.com/x/log.txt?x=17149949580000 kernel config: https://syzkaller.appspot.com/x/.config?x=f2baeae6059376eb dashboard link: https://syzkaller.appspot.com/bug?extid=f272bbfbf8498ddadea5 compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=135696c6580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15dd4679580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/ec03d2a9ef9c/disk-e6a5d573.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/4d46598728d1/vmlinux-e6a5d573.xz kernel image: https://storage.googleapis.com/syzbot-assets/cae584a81da1/bzImage-e6a5d573.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+f272bbfbf8498ddadea5@syzkaller.appspotmail.com INFO: task syz-executor261:5647 blocked for more than 143 seconds. Not tainted syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor261 state:D stack:24224 pid:5647 tgid:5646 ppid:5643 task_flags:0x480140 flags:0x00080002 Call Trace: context_switch kernel/sched/core.c:5510 [inline] __schedule+0x17d9/0x56c0 kernel/sched/core.c:7234 __schedule_loop kernel/sched/core.c:7311 [inline] schedule+0x164/0x2b0 kernel/sched/core.c:7326 blk_mq_freeze_queue_wait+0x101/0x180 block/blk-mq.c:191 blk_mq_freeze_queue include/linux/blk-mq.h:956 [inline] queue_limits_commit_update_frozen+0x55/0xd0 block/blk-settings.c:590 nbd_set_size+0x454/0x680 drivers/block/nbd.c:374 nbd_genl_size_set drivers/block/nbd.c:2106 [inline] nbd_genl_reconfigure+0x7e9/0x1e80 drivers/block/nbd.c:2410 genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2556 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x7bb/0x940 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1900 sock_sendmsg_nosec+0x13a/0x180 net/socket.c:775 __sock_sendmsg net/socket.c:790 [inline] ____sys_sendmsg+0x54e/0x850 net/socket.c:2684 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2738 __sys_sendmsg net/socket.c:2770 [inline] __do_sys_sendmsg net/socket.c:2775 [inline] __se_sys_sendmsg net/socket.c:2773 [inline] __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2773 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f289ec90aa9 RSP: 002b:00007f289ec611d8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f289ed3bb88 RCX: 00007f289ec90aa9 RDX: 0000000000080000 RSI: 0000200000000c40 RDI: 0000000000000006 RBP: 00007f289ed3bb80 R08: 35203a6b63617473 R09: 35203a6b63617473 R10: 35203a6b63617473 R11: 0000000000000246 R12: 00007f289ed0c4a0 R13: 0000200000000c00 R14: 0000200000000c50 R15: 0000200000000c40 Showing all locks held in the system: 1 lock held by khungtaskd/31: #0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline] #0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775 2 locks held by kworker/u9:0/50: #0: ffff888026e67940 ((wq_completion)nbd0-recv){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline] #0: ffff888026e67940 ((wq_completion)nbd0-recv){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3405 #1: ffffc90000bb7c40 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline] #1: ffffc90000bb7c40 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3405 7 locks held by kworker/u8:4/62: #0: ffff88801b06c140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline] #0: ffff88801b06c140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3405 #1: ffffc9000203fc40 ((work_completion)(&(&kfence_timer)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline] #1: ffffc9000203fc40 ((work_completion)(&(&kfence_timer)->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3405 #2: ffffffff8e9e75f0 (cpu_hotplug_lock){++++}-{0:0}, at: lock_timer_base kernel/time/timer.c:1004 [inline] #2: ffffffff8e9e75f0 (cpu_hotplug_lock){++++}-{0:0}, at: __mod_timer+0x1a9/0xed0 kernel/time/timer.c:1085 #3: ffffffff9a991198 (&obj_hash[i].lock){-.-.}-{2:2}, at: debug_object_activate+0xb7/0x420 lib/debugobjects.c:873 #4: ffffffff8e9fd1a0 (text_mutex){+.+.}-{4:4}, at: arch_jump_label_transform_apply+0x17/0x30 arch/x86/kernel/jump_label.c:145 #5: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #5: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline] #5: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: __pte_offset_map+0x29/0x240 mm/pgtable-generic.c:290 #6: ffff88801b060618 (ptlock_ptr(ptdesc)#2){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:342 [inline] #6: ffff88801b060618 (ptlock_ptr(ptdesc)#2){+.+.}-{3:3}, at: pte_offset_map_lock+0x13d/0x210 mm/pgtable-generic.c:404 2 locks held by getty/5362: #0: ffff88803616f0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243 #1: ffffc900032332e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360 drivers/tty/n_tty.c:2211 1 lock held by udevd/5644: #0: ffff888026e70350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xde/0xd70 block/bdev.c:948 6 locks held by syz-executor261/5647: #0: ffffffff90099b68 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217 #1: ffffffff900999a0 (genl_mutex){+.+.}-{4:4}, at: genl_lock net/netlink/genetlink.c:35 [inline] #1: ffffffff900999a0 (genl_mutex){+.+.}-{4:4}, at: genl_op_lock net/netlink/genetlink.c:60 [inline] #1: ffffffff900999a0 (genl_mutex){+.+.}-{4:4}, at: genl_rcv_msg+0x10b/0x7a0 net/netlink/genetlink.c:1208 #2: ffff888026e60260 (&nbd->config_lock){+.+.}-{4:4}, at: nbd_genl_reconfigure+0x4bc/0x1e80 drivers/block/nbd.c:2401 #3: ffff888026f747c8 (&q->limits_lock){+.+.}-{4:4}, at: queue_limits_start_update include/linux/blkdev.h:1103 [inline] #3: ffff888026f747c8 (&q->limits_lock){+.+.}-{4:4}, at: nbd_set_size+0x263/0x680 drivers/block/nbd.c:354 #4: ffff888026f74190 (&q->q_usage_counter(io)#49){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:956 [inline] #4: ffff888026f74190 (&q->q_usage_counter(io)#49){++++}-{0:0}, at: queue_limits_commit_update_frozen+0x55/0xd0 block/blk-settings.c:590 #5: ffff888026f741c8 (&q->q_usage_counter(queue)#33){+.+.}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:956 [inline] #5: ffff888026f741c8 (&q->q_usage_counter(queue)#33){+.+.}-{0:0}, at: queue_limits_commit_update_frozen+0x55/0xd0 block/blk-settings.c:590 ============================================= NMI backtrace for cpu 1 CPU: 1 UID: 0 PID: 31 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:122 nmi_trigger_cpumask_backtrace+0x17a/0x380 lib/nmi_backtrace.c:65 trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline] __sys_info lib/sys_info.c:157 [inline] sys_info+0x135/0x170 lib/sys_info.c:165 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline] watchdog+0xfd7/0x1030 kernel/hung_task.c:561 kthread+0x388/0x470 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 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 07/24/2026 RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:64 Code: bb 7c 02 c3 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 b3 ce 15 00 fb f4 4c 07 03 00 cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90 RSP: 0018:ffffffff8e807de0 EFLAGS: 00000246 RAX: 00000000000de999 RBX: ffffffff819b433c RCX: 0000000080000001 RDX: 0000000000000001 RSI: ffffffff8e23666e RDI: ffffffff8c4bbf80 RBP: ffffffff8e807eb8 R08: ffff8880b86338db R09: 1ffff110170c671b R10: dffffc0000000000 R11: ffffed10170c671c R12: 0000000000000000 R13: 1ffffffff1d11de8 R14: 1ffffffff1d00fc4 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff888124f4c000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000561f5d89e168 CR3: 000000000e946000 CR4: 00000000003526f0 Call Trace: arch_safe_halt arch/x86/kernel/process.c:767 [inline] default_idle+0x9/0x20 arch/x86/kernel/process.c:768 default_idle_call+0x72/0xb0 kernel/sched/idle.c:122 cpuidle_idle_call kernel/sched/idle.c:199 [inline] do_idle+0x1cc/0x540 kernel/sched/idle.c:355 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:454 rest_init+0x2de/0x300 init/main.c:717 start_kernel+0x392/0x3e0 init/main.c:1175 x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310 x86_64_start_kernel+0x137/0x1b0 arch/x86/kernel/head64.c:291 common_startup_64+0x13e/0x157 --- 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.