Re: [syzbot] [net?] INFO: task hung in linkwatch_event (4)

[syzbot <syzbot+2ba2d70f288cf61174e4@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    932d2d1fcb2b Merge tag 'dlm-6.12' of git://git.kernel.org/..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=120d6607980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c208b3605ba9ec44
dashboard link: https://syzkaller.appspot.com/bug?extid=2ba2d70f288cf61174e4
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1069b69f980000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-932d2d1f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/fbcb7198214b/vmlinux-932d2d1f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/418eaebf4817/bzImage-932d2d1f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2ba2d70f288cf61174e4@syzkaller.appspotmail.com

INFO: task kworker/u4:3:5245 blocked for more than 143 seconds.
      Not tainted 6.11.0-syzkaller-05442-g932d2d1fcb2b #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:3    state:D stack:23120 pid:5245  tgid:5245  ppid:2      flags:0x00004000
Workqueue: events_unbound linkwatch_event
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5188 [inline]
 __schedule+0x1800/0x4a60 kernel/sched/core.c:6529
 __schedule_loop kernel/sched/core.c:6606 [inline]
 schedule+0x14b/0x320 kernel/sched/core.c:6621
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6678
 __mutex_lock_common kernel/locking/mutex.c:684 [inline]
 __mutex_lock+0x6a4/0xd70 kernel/locking/mutex.c:752
 linkwatch_event+0xe/0x60 net/core/link_watch.c:276
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0xa63/0x1850 kernel/workqueue.c:3310
 worker_thread+0x870/0xd30 kernel/workqueue.c:3391
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/0:1/9:
 #0: ffff88801ac75948 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3204 [inline]
 #0: ffff88801ac75948 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1850 kernel/workqueue.c:3310
 #1: ffffc900003b7d00 ((reg_check_chans).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3205 [inline]
 #1: ffffc900003b7d00 ((reg_check_chans).work){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1850 kernel/workqueue.c:3310
 #2: ffffffff8fcc4d08 (rtnl_mutex){+.+.}-{3:3}, at: reg_check_chans_work+0x99/0xfd0 net/wireless/reg.c:2480
2 locks held by kworker/u4:0/11:
 #0: ffff88801ac79148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3204 [inline]
 #0: ffff88801ac79148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1850 kernel/workqueue.c:3310
 #1: ffffc900003d7d00 ((work_completion)(&sub_info->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3205 [inline]
 #1: ffffc900003d7d00 ((work_completion)(&sub_info->work)){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1850 kernel/workqueue.c:3310
1 lock held by khungtaskd/25:
 #0: ffffffff8e938b60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
 #0: ffffffff8e938b60 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffffffff8e938b60 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x2a0 kernel/locking/lockdep.c:6701
2 locks held by kworker/u4:10/2886:
2 locks held by dhcpcd/4810:
 #0: ffff88801ca91c40 (&vma->vm_lock->lock){++++}-{3:3}, at: vma_start_read include/linux/mm.h:700 [inline]
 #0: ffff88801ca91c40 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x2f9/0x6e0 mm/memory.c:6015
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __perform_reclaim mm/page_alloc.c:3898 [inline]
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_direct_reclaim mm/page_alloc.c:3923 [inline]
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_slowpath+0xcfb/0x2390 mm/page_alloc.c:4329
1 lock held by dhcpcd/4811:
 #0: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __perform_reclaim mm/page_alloc.c:3898 [inline]
 #0: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_direct_reclaim mm/page_alloc.c:3923 [inline]
 #0: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_slowpath+0xcfb/0x2390 mm/page_alloc.c:4329
2 locks held by getty/4894:
 #0: ffff88801dfa10a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000039b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6a6/0x1e00 drivers/tty/n_tty.c:2211
2 locks held by syz-execprog/5124:
 #0: ffff88803fe4bc40 (&vma->vm_lock->lock){++++}-{3:3}, at: vma_start_read include/linux/mm.h:700 [inline]
 #0: ffff88803fe4bc40 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x2f9/0x6e0 mm/memory.c:6015
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __perform_reclaim mm/page_alloc.c:3898 [inline]
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_direct_reclaim mm/page_alloc.c:3923 [inline]
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_slowpath+0xcfb/0x2390 mm/page_alloc.c:4329
1 lock held by syz-executor/5122:
 #0: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __perform_reclaim mm/page_alloc.c:3898 [inline]
 #0: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_direct_reclaim mm/page_alloc.c:3923 [inline]
 #0: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_slowpath+0xcfb/0x2390 mm/page_alloc.c:4329
3 locks held by kworker/u4:1/5157:
 #0: ffff888035d58948 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3204 [inline]
 #0: ffff888035d58948 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1850 kernel/workqueue.c:3310
 #1: ffffc90002ddfd00 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3205 [inline]
 #1: ffffc90002ddfd00 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1850 kernel/workqueue.c:3310
 #2: ffffffff8fcc4d08 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_verify_work+0x19/0x30 net/ipv6/addrconf.c:4736
3 locks held by kworker/u4:3/5245:
 #0: ffff88801ac79148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3204 [inline]
 #0: ffff88801ac79148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1850 kernel/workqueue.c:3310
 #1: ffffc9000246fd00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3205 [inline]
 #1: ffffc9000246fd00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1850 kernel/workqueue.c:3310
 #2: ffffffff8fcc4d08 (rtnl_mutex){+.+.}-{3:3}, at: linkwatch_event+0xe/0x60 net/core/link_watch.c:276
2 locks held by kworker/u4:5/5250:
 #0: ffff88801ac79148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3204 [inline]
 #0: ffff88801ac79148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1850 kernel/workqueue.c:3310
 #1: ffffc9000249fd00 ((work_completion)(&sub_info->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3205 [inline]
 #1: ffffc9000249fd00 ((work_completion)(&sub_info->work)){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1850 kernel/workqueue.c:3310
2 locks held by kworker/u4:7/5252:
 #0: ffff88801fe3e998 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:560
 #1: ffff88801fe28948 (&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_switch+0x441/0x770 kernel/sched/psi.c:989
2 locks held by syz-executor/5732:
 #0: ffff888035e21070 (&vma->vm_lock->lock){++++}-{3:3}, at: vma_start_read include/linux/mm.h:700 [inline]
 #0: ffff888035e21070 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x2f9/0x6e0 mm/memory.c:6015
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __perform_reclaim mm/page_alloc.c:3898 [inline]
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_direct_reclaim mm/page_alloc.c:3923 [inline]
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_slowpath+0xcfb/0x2390 mm/page_alloc.c:4329
2 locks held by udevd/5760:
 #0: ffff8880119e8658 (&vma->vm_lock->lock){++++}-{3:3}, at: vma_start_read include/linux/mm.h:700 [inline]
 #0: ffff8880119e8658 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x2f9/0x6e0 mm/memory.c:6015
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __perform_reclaim mm/page_alloc.c:3898 [inline]
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_direct_reclaim mm/page_alloc.c:3923 [inline]
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_slowpath+0xcfb/0x2390 mm/page_alloc.c:4329
8 locks held by syz-executor/5784:
 #0: ffff88801ed72420 (sb_writers#8){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2930 [inline]
 #0: ffff88801ed72420 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x224/0xc90 fs/read_write.c:679
 #1: ffff888046575888 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1ea/0x500 fs/kernfs/file.c:325
 #2: ffff8880354e4968 (kn->active#59){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x20e/0x500 fs/kernfs/file.c:326
 #3: ffffffff8f561ca8 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: new_device_store+0x1b4/0x890 drivers/net/netdevsim/bus.c:166
 #4: ffff8880441160e8 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:1009 [inline]
 #4: ffff8880441160e8 (&dev->mutex){....}-{3:3}, at: __device_attach+0x8e/0x520 drivers/base/dd.c:1004
 #5: ffff888044110250 (&devlink->lock_key#23){+.+.}-{3:3}, at: nsim_drv_probe+0xcb/0xb80 drivers/net/netdevsim/dev.c:1534
 #6: ffffffff8fcc4d08 (rtnl_mutex){+.+.}-{3:3}, at: nsim_init_netdevsim drivers/net/netdevsim/netdev.c:678 [inline]
 #6: ffffffff8fcc4d08 (rtnl_mutex){+.+.}-{3:3}, at: nsim_create+0x408/0x890 drivers/net/netdevsim/netdev.c:750
 #7: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __perform_reclaim mm/page_alloc.c:3898 [inline]
 #7: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_direct_reclaim mm/page_alloc.c:3923 [inline]
 #7: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_slowpath+0xcfb/0x2390 mm/page_alloc.c:4329
2 locks held by udevd/5785:
 #0: ffff8880122dd148 (&vma->vm_lock->lock){++++}-{3:3}, at: vma_start_read include/linux/mm.h:700 [inline]
 #0: ffff8880122dd148 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x2f9/0x6e0 mm/memory.c:6015
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __perform_reclaim mm/page_alloc.c:3898 [inline]
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_direct_reclaim mm/page_alloc.c:3923 [inline]
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_slowpath+0xcfb/0x2390 mm/page_alloc.c:4329
2 locks held by udevd/5788:
 #0: ffff888011dcd8e0 (&vma->vm_lock->lock){++++}-{3:3}, at: vma_start_read include/linux/mm.h:700 [inline]
 #0: ffff888011dcd8e0 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x2f9/0x6e0 mm/memory.c:6015
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __perform_reclaim mm/page_alloc.c:3898 [inline]
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_direct_reclaim mm/page_alloc.c:3923 [inline]
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_slowpath+0xcfb/0x2390 mm/page_alloc.c:4329
1 lock held by modprobe/5813:
 #0: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __perform_reclaim mm/page_alloc.c:3898 [inline]
 #0: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_direct_reclaim mm/page_alloc.c:3923 [inline]
 #0: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_slowpath+0xcfb/0x2390 mm/page_alloc.c:4329
2 locks held by modprobe/5814:
 #0: ffff88804c225df0 (&vma->vm_lock->lock){++++}-{3:3}, at: vma_start_read include/linux/mm.h:700 [inline]
 #0: ffff88804c225df0 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x2f9/0x6e0 mm/memory.c:6015
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __perform_reclaim mm/page_alloc.c:3898 [inline]
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_direct_reclaim mm/page_alloc.c:3923 [inline]
 #1: ffffffff8ea300e0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_slowpath+0xcfb/0x2390 mm/page_alloc.c:4329

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 25 Comm: khungtaskd Not tainted 6.11.0-syzkaller-05442-g932d2d1fcb2b #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:93 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119
 nmi_cpu_backtrace+0x49c/0x4d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x198/0x320 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:223 [inline]
 watchdog+0xff4/0x1040 kernel/hung_task.c:379
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>


---
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.