syzbot

INFO: task syz.2.1136:14822 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.1136      state:D stack:25640 pid:14822 tgid:14813 ppid:5598   task_flags:0x400140 flags:0x00080003
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x16dc/0x5500 kernel/sched/core.c:7234
 __schedule_loop kernel/sched/core.c:7311 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7326
 schedule_timeout+0xc0/0x2c0 kernel/time/sleep_timeout.c:75
 do_wait_for_common kernel/sched/completion.c:100 [inline]
 __wait_for_common kernel/sched/completion.c:121 [inline]
 wait_for_common kernel/sched/completion.c:132 [inline]
 wait_for_completion+0x2ca/0x5e0 kernel/sched/completion.c:153
 kthread_flush_worker+0x138/0x1a0 kernel/kthread.c:1579
 __alloc_workqueue+0x16b2/0x2060 kernel/workqueue.c:5924
 alloc_workqueue_va kernel/workqueue.c:5946 [inline]
 alloc_workqueue_noprof+0xe3/0x210 kernel/workqueue.c:5962
 btrfs_init_workqueues+0x184/0x630 fs/btrfs/disk-io.c:1971
 open_ctree+0x1503/0x41c0 fs/btrfs/disk-io.c:3523
 btrfs_fill_super fs/btrfs/super.c:982 [inline]
 btrfs_get_tree_super fs/btrfs/super.c:1971 [inline]
 btrfs_get_tree_subvol fs/btrfs/super.c:2114 [inline]
 btrfs_get_tree+0x1084/0x1980 fs/btrfs/super.c:2148
 vfs_get_tree+0x92/0x2a0 fs/super.c:1694
 fc_mount fs/namespace.c:1198 [inline]
 do_new_mount_fc fs/namespace.c:3765 [inline]
 do_new_mount+0x319/0xdc0 fs/namespace.c:3841
 do_mount fs/namespace.c:4174 [inline]
 __do_sys_mount fs/namespace.c:4390 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4367
 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: 0033:0x7f1fad8af0ca
RSP: 002b:00007f1fabb05e58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f1fabb05ee0 RCX: 00007f1fad8af0ca
RDX: 0000200000005100 RSI: 0000200000005140 RDI: 00007f1fabb05ea0
RBP: 0000200000005100 R08: 00007f1fabb05ee0 R09: 0000000000018000
R10: 0000000000018000 R11: 0000000000000246 R12: 0000200000005140
R13: 00007f1fabb05ea0 R14: 00000000000050d4 R15: 0000200000005180
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/38:
 #0: ffffffff8dfc2fc0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #0: ffffffff8dfc2fc0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
 #0: ffffffff8dfc2fc0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
5 locks held by kworker/u8:7/245:
2 locks held by udevd/4960:
2 locks held by getty/5347:
 #0: ffff8880365ce0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90003cc62e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x460/0x1360 drivers/tty/n_tty.c:2211
1 lock held by syz-executor/5594:
4 locks held by syz-executor/5595:
1 lock held by udevd/8120:
1 lock held by syz.2.1136/14822:
 #0: ffff88803e2920d0 (&type->s_umount_key#60/1){+.+.}-{4:4}, at: alloc_super fs/super.c:345 [inline]
 #0: ffff88803e2920d0 (&type->s_umount_key#60/1){+.+.}-{4:4}, at: sget_fc+0x938/0x1910 fs/super.c:766
1 lock held by syz.0.1325/16244:
4 locks held by syz.5.1329/16255:

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 38 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 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
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 8120 Comm: udevd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:preempt_count_add+0x42/0x190 kernel/sched/core.c:5985
Code: 7c 99 48 c1 e8 03 42 0f b6 04 38 84 c0 0f 85 ea 00 00 00 83 3d fe a3 e8 17 00 75 07 65 8b 05 a5 5e dd 10 65 01 3d 9e 5e dd 10 <48> c7 c0 80 35 7c 99 48 c1 e8 03 42 0f b6 04 38 84 c0 0f 85 e5 00
RSP: 0018:ffffc9001f327248 EFLAGS: 00000082
RAX: 0000000080000000 RBX: 0000000000000297 RCX: ffffffff997c3503
RDX: 0000000000000000 RSI: ffffffff8ba94360 RDI: 0000000000000001
RBP: ffff8880b8842d40 R08: ffffffff8f8afef7 R09: 1ffffffff1f15fde
R10: dffffc0000000000 R11: fffffbfff1f15fdf R12: dffffc0000000000
R13: ffff88805cd05d00 R14: ffff8880b8842d40 R15: dffffc0000000000
FS:  00007fa37584a880(0000) GS:ffff888126111000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fea959d5690 CR3: 000000003ca6a000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:131 [inline]
 _raw_spin_lock_irqsave+0x24/0x60 kernel/locking/spinlock.c:166
 rt_mutex_slowtrylock kernel/locking/rtmutex.c:1404 [inline]
 __rt_spin_trylock kernel/locking/spinlock_rt.c:123 [inline]
 rt_spin_trylock+0x56/0x2b0 kernel/locking/spinlock_rt.c:135
 free_unref_folios+0x117d/0x1910 mm/page_alloc.c:3062
 folios_put_refs+0x815/0x920 mm/swap.c:1057
 free_pages_and_swap_cache+0x41e/0x490 mm/swap_state.c:589
 __tlb_batch_free_encoded_pages mm/mmu_gather.c:138 [inline]
 tlb_batch_pages_flush mm/mmu_gather.c:151 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:417 [inline]
 tlb_flush_mmu+0x6d3/0xa30 mm/mmu_gather.c:424
 tlb_finish_mmu+0xf4/0x220 mm/mmu_gather.c:549
 unmap_region+0x2a5/0x330 mm/vma.c:491
 vms_clear_ptes mm/vma.c:1303 [inline]
 vms_complete_munmap_vmas+0x427/0xbe0 mm/vma.c:1345
 do_vmi_align_munmap+0x3bd/0x4d0 mm/vma.c:1604
 do_vmi_munmap+0x252/0x2d0 mm/vma.c:1652
 __vm_munmap+0x241/0x3e0 mm/vma.c:3288
 __do_sys_munmap mm/mmap.c:1079 [inline]
 __se_sys_munmap mm/mmap.c:1076 [inline]
 __x64_sys_munmap+0x60/0x70 mm/mmap.c:1076
 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: 0033:0x7fa3759af097
Code: 73 01 c3 48 8b 0d 61 2d 0d 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 31 2d 0d 00 f7 d8 64 89 01 48
RSP: 002b:00007ffc90b5b608 EFLAGS: 00000246 ORIG_RAX: 000000000000000b
RAX: ffffffffffffffda RBX: 000055fcc51fd1e0 RCX: 00007fa3759af097
RDX: 000055fcc51fa6d8 RSI: 0000000000000200 RDI: 00007fa374ed8000
RBP: 000055fcc5204420 R08: 000055fcc51fd210 R09: 0000000000000003
R10: 000055fcc5204410 R11: 0000000000000246 R12: 00007fa37608c7c0
R13: 00007fa37608e39c R14: 0000000000000022 R15: 0000000000000001
 </TASK>