BUG: soft lockup in tty_release

Status: premoderation: reported on 2026/10/11 15:31
Reported-by: syzbot+fcf46cca7830d6cf0124@syzkaller.appspotmail.com
First crash: 20h46m, last: 20h46m
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in tty_release (2) mm 1 4 614d 705d 0/29 auto-obsoleted due to no activity on 2025/05/06 09:10
upstream INFO: rcu detected stall in tty_release (3) net bluetooth 1 2 416d 471d 0/29 auto-obsoleted due to no activity on 2025/11/19 23:52
upstream INFO: rcu detected stall in tty_release serial 1 3 817d 885d 0/29 auto-obsoleted due to no activity on 2024/10/15 04:06
upstream INFO: rcu detected stall in tty_release (4) prio:normal serial 1 1 194d 194d 0/29 auto-obsoleted due to no activity on 2026/06/30 05:25

Sample crash report:
watchdog: BUG: soft lockup - CPU#0 stuck for 144s! [syz.0.357:1785]
Modules linked in:
CPU: 0 PID: 1785 Comm: syz.0.357 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
RIP: 0010:arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
RIP: 0010:kvm_wait+0x105/0x150 arch/x86/kernel/kvm.c:918
Code: 11 d6 03 f4 eb 87 fa 48 89 f8 48 c1 e8 03 42 0f b6 04 30 84 c0 75 3f 0f b6 07 40 38 f0 75 10 66 90 0f 00 2d 1d 11 d6 03 fb f4 <e9> 5e ff ff ff fb e9 58 ff ff ff e8 cb 0f 7e 03 89 f9 80 e1 07 38
RSP: 0018:ffffc900009c71c0 EFLAGS: 00000246
RAX: 0000000000000003 RBX: ffffffff8660d5c4 RCX: ffffffff815013fc
RDX: 0000000000000001 RSI: 0000000000000003 RDI: ffffffff8660d5c4
RBP: ffffc900009c7250 R08: ffffffff8660d5c4 R09: 1ffffffff0cc1ab8
R10: dffffc0000000000 R11: fffffbfff0cc1ab9 R12: ffff88823ff52880
R13: dffffc0000000000 R14: dffffc0000000000 R15: 1ffff92000138e38
FS:  0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2ed1aff8 CR3: 0000000118f54000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 pv_wait arch/x86/include/asm/paravirt.h:597 [inline]
 pv_wait_head_or_lock kernel/locking/qspinlock_paravirt.h:470 [inline]
 __pv_queued_spin_lock_slowpath+0x605/0x9b0 kernel/locking/qspinlock.c:508
 pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:585 [inline]
 queued_spin_lock_slowpath+0x47/0x50 arch/x86/include/asm/qspinlock.h:51
 queued_spin_lock include/asm-generic/qspinlock.h:85 [inline]
 do_raw_spin_lock include/linux/spinlock.h:188 [inline]
 __raw_spin_lock include/linux/spinlock_api_smp.h:143 [inline]
 _raw_spin_lock+0xe4/0xf0 kernel/locking/spinlock.c:154
 spin_lock include/linux/spinlock.h:364 [inline]
 write_seqlock include/linux/seqlock.h:937 [inline]
 lock_mount_hash fs/namespace.c:113 [inline]
 mntput_no_expire+0x148/0x6b0 fs/namespace.c:1190
 mntput+0x5f/0xc0 fs/namespace.c:1245
 simple_release_fs+0xb0/0xe0 fs/libfs.c:711
 remove_one+0x103/0x140 fs/debugfs/inode.c:723
 simple_recursive_removal+0x63a/0x830 fs/libfs.c:296
 debugfs_remove+0x56/0x70 fs/debugfs/inode.c:745
 hci_release_dev+0xa2/0x14c0 net/bluetooth/hci_core.c:4072
 bt_host_release+0x82/0x90 net/bluetooth/hci_sysfs.c:85
 device_release+0x96/0x1c0 drivers/base/core.c:-1
 kobject_cleanup lib/kobject.c:713 [inline]
 kobject_release lib/kobject.c:744 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x18a/0x270 lib/kobject.c:761
 put_device+0x1f/0x30 drivers/base/core.c:3530
 hci_free_dev+0x1c/0x20 net/bluetooth/hci_core.c:3899
 hci_uart_tty_close+0x2b9/0x2f0 drivers/bluetooth/hci_ldisc.c:581
 tty_ldisc_close drivers/tty/tty_ldisc.c:474 [inline]
 tty_ldisc_kill+0x10d/0x210 drivers/tty/tty_ldisc.c:629
 tty_ldisc_release+0x1a5/0x200 drivers/tty/tty_ldisc.c:803
 tty_release_struct+0x29/0xe0 drivers/tty/tty_io.c:1708
 tty_release+0xc87/0x1330 drivers/tty/tty_io.c:1880
 __fput+0x22b/0x900 fs/file_table.c:311
 ____fput+0x15/0x20 fs/file_table.c:339
 task_work_run+0x127/0x190 kernel/task_work.c:188
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0xb70/0x29a0 kernel/exit.c:896
 do_group_exit+0x149/0x310 kernel/exit.c:1010
 get_signal+0x64f/0x1430 kernel/signal.c:2920
 arch_do_signal_or_restart+0xe2/0x1100 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:157 [inline]
 exit_to_user_mode_loop+0xa7/0xe0 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:217
 irqentry_exit_to_user_mode+0x9/0x10 kernel/entry/common.c:323
 irqentry_exit+0x12/0x40 kernel/entry/common.c:414
 exc_page_fault+0x5e/0xb0 arch/x86/mm/fault.c:1563
 asm_exc_page_fault+0x27/0x30 arch/x86/include/asm/idtentry.h:606
RIP: 0033:0x7fdf1c862c07
Code: Unable to access opcode bytes at RIP 0x7fdf1c862bdd.
RSP: 002b:00007fdf1b3c6120 EFLAGS: 00010202
RAX: 0000000000000000 RBX: 000000000000000b RCX: 00007fdf1c9ad1d9
RDX: 00007fdf1b3c6140 RSI: 00007fdf1b3c6270 RDI: 000000000000000b
RBP: 00007fdf1ca44888 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007fdf1cc35128 R14: 00007fdf1cc35090 R15: 00007ffe5a115f18
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 1921 Comm: syz.0.396 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:next_peer fs/pnode.c:19 [inline]
RIP: 0010:do_make_slave fs/pnode.c:100 [inline]
RIP: 0010:change_mnt_propagation+0x127/0xa20 fs/pnode.c:128
Code: 8f 14 ec ff 4d 39 2e 74 7a 49 81 c4 d0 00 00 00 4c 89 e0 48 c1 e8 03 42 80 3c 38 00 74 08 4c 89 e7 e8 6d 14 ec ff 4d 8b 24 24 <49> 01 dc 4c 3b 65 b8 74 5e e8 bb 93 ac ff eb af 49 8d 5d 30 49 89
RSP: 0018:ffffc90002f4fad8 EFLAGS: 00000246
RAX: 1ffff1102259f48a RBX: ffffffffffffff30 RCX: ffff88810af63c00
RDX: 0000000000000000 RSI: 0000000000040000 RDI: 0000000000100000
RBP: ffffc90002f4fb30 R08: ffff88813f681d27 R09: ffff88813f681d18
R10: dffffc0000000000 R11: ffffed1027ed03a5 R12: ffff888112cfb410
R13: ffff888111e97880 R14: ffff888112cfa3a0 R15: dffffc0000000000
FS:  00007fdf1b4066c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4a9b7b6fd0 CR3: 0000000128ea3000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
 <TASK>
 umount_tree+0xcd2/0xe40 fs/namespace.c:1560
 attach_recursive_mnt+0x71a/0x15c0 fs/namespace.c:2242
 do_move_mount+0x5be/0x7b0 fs/namespace.c:2872
 __do_sys_move_mount fs/namespace.c:3811 [inline]
 __se_sys_move_mount+0x259/0xb10 fs/namespace.c:3767
 __x64_sys_move_mount+0xbf/0xd0 fs/namespace.c:3767
 x64_sys_call+0x5df/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:430
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fdf1c9ad1d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fdf1b406028 EFLAGS: 00000246 ORIG_RAX: 00000000000001ad
RAX: ffffffffffffffda RBX: 00007fdf1cc34fa0 RCX: 00007fdf1c9ad1d9
RDX: ffffffffffffff9c RSI: 0000200000000140 RDI: 0000000000000003
RBP: 00007fdf1ca44888 R08: 0000000000000000 R09: 0000000000000000
R10: 0000200000000180 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdf1cc35038 R14: 00007fdf1cc34fa0 R15: 00007ffe5a115f18
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/11 15:30 android13-5.15-lts d6c8aee048e0 4f92358f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 BUG: soft lockup in tty_release
* Struck through repros no longer work on HEAD.