syzbot

INFO: task syz.1.86:6368 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.86        state:D stack:29024 pid:6368  tgid:6363  ppid:5800   task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 <TASK>
 context_switch kernel/sched/core.c:5298 [inline]
 __schedule+0x1553/0x5240 kernel/sched/core.c:6911
 __schedule_loop kernel/sched/core.c:6993 [inline]
 schedule+0x164/0x360 kernel/sched/core.c:7008
 percpu_rwsem_wait+0x317/0x480 kernel/locking/percpu-rwsem.c:164
 __percpu_down_read+0xfc/0x140 kernel/locking/percpu-rwsem.c:180
 percpu_down_read_internal include/linux/percpu-rwsem.h:67 [inline]
 percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
 __sb_start_write include/linux/fs/super.h:19 [inline]
 sb_start_write+0x18e/0x1c0 include/linux/fs/super.h:125
 mnt_want_write+0x41/0x90 fs/namespace.c:493
 filename_create+0x154/0x370 fs/namei.c:4921
 filename_mkdirat+0xd2/0x520 fs/namei.c:5265
 __do_sys_mkdirat fs/namei.c:5293 [inline]
 __se_sys_mkdirat+0x35/0x150 fs/namei.c:5290
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f17b909b687
RSP: 002b:00007f17b72b3e58 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007f17b72b3ee0 RCX: 00007f17b909b687
RDX: 00000000000001ff RSI: 0000200000000000 RDI: 00000000ffffff9c
RBP: 00002000000002c0 R08: 0000200000000240 R09: 0000000000000000
R10: 00002000000002c0 R11: 0000000000000246 R12: 0000200000000000
R13: 00007f17b72b3ea0 R14: 0000000000000000 R15: 0000000000000000
 </TASK>

Showing all locks held in the system:
6 locks held by kworker/u8:0/12:
5 locks held by kworker/u8:1/13:
1 lock held by khungtaskd/38:
 #0: ffffffff8ddcb980 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 #0: ffffffff8ddcb980 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
 #0: ffffffff8ddcb980 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
3 locks held by kworker/u8:8/1396:
 #0: ffff888019c44138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3251 [inline]
 #0: ffff888019c44138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0xa52/0x18c0 kernel/workqueue.c:3359
 #1: ffffc90005ee7c40 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3252 [inline]
 #1: ffffc90005ee7c40 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0xa8d/0x18c0 kernel/workqueue.c:3359
 #2: ffffffff8f15d4b8 (rtnl_mutex){+.+.}-{4:4}, at: linkwatch_event+0xe/0x60 net/core/link_watch.c:313
2 locks held by kworker/u8:14/3500:
2 locks held by dhcpcd/5463:
 #0: ffff888032b64928 (nlk_cb_mutex-ROUTE){+.+.}-{4:4}, at: netlink_dump+0xe4/0xe80 net/netlink/af_netlink.c:2267
 #1: ffffffff8f15d4b8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
 #1: ffffffff8f15d4b8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_dumpit+0x92/0x200 net/core/rtnetlink.c:6848
2 locks held by getty/5559:
 #0: ffff888036e710a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90003e762e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x462/0x13c0 drivers/tty/n_tty.c:2211
1 lock held by udevd/5927:
7 locks held by udevd/6022:
1 lock held by syz.1.86/6368:
 #0: ffff888029292480 (sb_writers#17){++++}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:493
2 locks held by syz-executor/8451:
 #0: ffffffff8e8b84e8 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 #0: ffffffff8e8b84e8 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
 #0: ffffffff8e8b84e8 (&ops->srcu#2){.+.+}-{0:0}, at: rtnl_link_ops_get+0x23/0x250 net/core/rtnetlink.c:570
 #1: ffffffff8f15d4b8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
 #1: ffffffff8f15d4b8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
 #1: ffffffff8f15d4b8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x8a1/0x1be0 net/core/rtnetlink.c:4093
4 locks held by syz.0.466/8595:
 #0: ffff888025569498 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_global_lock_killable drivers/block/loop.c:118 [inline]
 #0: ffff888025569498 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_configure+0x37b/0xdf0 drivers/block/loop.c:1016
 #1: ffff8880b893a0b8 ((lock)){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
 #1: ffff8880b893a0b8 ((lock)){+.+.}-{3:3}, at: __radix_tree_preload+0x141/0x870 lib/radix-tree.c:334
 #2: ffffffff8ddcb980 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 #2: ffffffff8ddcb980 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
 #2: ffffffff8ddcb980 (rcu_read_lock){....}-{1:3}, at: __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline]
 #2: ffffffff8ddcb980 (rcu_read_lock){....}-{1:3}, at: rt_spin_lock+0x1e0/0x400 kernel/locking/spinlock_rt.c:57
 #3: ffff888019c4f100 (&root->kernfs_idr_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
 #3: ffff888019c4f100 (&root->kernfs_idr_lock){+.+.}-{3:3}, at: __kernfs_new_node+0x111/0x960 fs/kernfs/dir.c:642
1 lock held by syz.3.471/8604:

=============================================

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 38 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:161 [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:346 [inline]
 watchdog+0xfd9/0x1030 kernel/hung_task.c:515
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 8595 Comm: syz.0.466 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:__bfs kernel/locking/lockdep.c:1815 [inline]
RIP: 0010:__bfs_backwards kernel/locking/lockdep.c:1860 [inline]
RIP: 0010:check_irq_usage kernel/locking/lockdep.c:2796 [inline]
RIP: 0010:check_prev_add kernel/locking/lockdep.c:3169 [inline]
RIP: 0010:check_prevs_add kernel/locking/lockdep.c:3284 [inline]
RIP: 0010:validate_chain kernel/locking/lockdep.c:3908 [inline]
RIP: 0010:__lock_acquire+0x197b/0x2cf0 kernel/locking/lockdep.c:5237
Code: 13 25 ff 0f 00 00 39 05 5f 58 b6 11 73 06 89 05 57 58 b6 11 48 8b 02 48 89 df 4c 39 e8 0f 84 2c fe ff ff 4c 89 60 30 48 8b 00 <4c> 39 e8 75 f4 48 89 df e9 18 fe ff ff 48 89 fb 48 c7 c7 d0 8c c9
RSP: 0018:ffffc9000725e5a8 EFLAGS: 00000002
RAX: ffffffff95fd9018 RBX: 00000000000003cd RCX: 00000000000000c8
RDX: ffffffff95de0b48 RSI: ffff88802c2d4980 RDI: 00000000000003cd
RBP: a9217127da4edf36 R08: ffffc9000725e570 R09: 0000000000000020
R10: dffffc0000000000 R11: ffffffff81a0a150 R12: ffffffff95e93738
R13: ffffffff92f9fb58 R14: ffff88802c2d3d00 R15: 00000000000000c7
FS:  00007f0c1c8fe6c0(0000) GS:ffff888126432000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3d3b51dd58 CR3: 000000002d5f6000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
 _raw_spin_lock_nested+0x32/0x50 kernel/locking/spinlock.c:378
 raw_spin_rq_lock_nested+0x31/0x150 kernel/sched/core.c:647
 raw_spin_rq_lock kernel/sched/sched.h:1618 [inline]
 _task_rq_lock+0xbc/0x470 kernel/sched/core.c:747
 class_task_rq_lock_constructor kernel/sched/sched.h:1920 [inline]
 migrate_disable_switch kernel/sched/core.c:2366 [inline]
 __schedule+0x16d3/0x5240 kernel/sched/core.c:6795
 __schedule_loop kernel/sched/core.c:6993 [inline]
 schedule_rtlock+0x30/0x70 kernel/sched/core.c:7072
 rtlock_slowlock_locked+0x3638/0x3c80 kernel/locking/rtmutex.c:1868
 rtlock_slowlock kernel/locking/rtmutex.c:1895 [inline]
 rtlock_lock kernel/locking/spinlock_rt.c:43 [inline]
 __rt_spin_lock kernel/locking/spinlock_rt.c:49 [inline]
 rt_spin_lock+0x165/0x400 kernel/locking/spinlock_rt.c:57
 spin_lock include/linux/spinlock_rt.h:45 [inline]
 __kernfs_new_node+0x111/0x960 fs/kernfs/dir.c:642
 kernfs_new_node+0x102/0x210 fs/kernfs/dir.c:718
 kernfs_create_dir_ns+0x44/0x130 fs/kernfs/dir.c:1088
 internal_create_group+0x425/0x1180 fs/sysfs/group.c:176
 loop_sysfs_init drivers/block/loop.c:731 [inline]
 loop_configure+0x97a/0xdf0 drivers/block/loop.c:1076
 lo_ioctl+0x447/0x1fc0 drivers/block/loop.c:1534
 blkdev_ioctl+0x5e6/0x750 block/ioctl.c:804
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f0c1e6ac4ab
Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00
RSP: 002b:00007f0c1c8fddb0 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007f0c1e6ac4ab
RDX: 0000000000000003 RSI: 0000000000004c00 RDI: 0000000000000004
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
R13: 00007f0c1c8fdee0 R14: 00007f0c1c8fdea0 R15: 00007f0c144de000
 </TASK>