syzbot

INFO: task syz.6.1413:18170 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.6.1413      state:D stack:28952 pid:18170 tgid:18143 ppid:15562  task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x145f/0x5070 kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 rt_mutex_schedule+0x77/0xf0 kernel/sched/core.c:7241
 rt_mutex_slowlock_block kernel/locking/rtmutex.c:1647 [inline]
 __rt_mutex_slowlock kernel/locking/rtmutex.c:1721 [inline]
 __rt_mutex_slowlock_locked+0x1dfe/0x25e0 kernel/locking/rtmutex.c:1760
 rt_mutex_slowlock+0xb5/0x160 kernel/locking/rtmutex.c:1800
 __rt_mutex_lock kernel/locking/rtmutex.c:1815 [inline]
 rwbase_write_lock+0x14f/0x750 kernel/locking/rwbase_rt.c:244
 inode_lock_nested include/linux/fs.h:1072 [inline]
 lock_rename fs/namei.c:3721 [inline]
 __start_renaming+0x148/0x410 fs/namei.c:3817
 do_renameat2+0x399/0x8f0 fs/namei.c:6031
 __do_sys_rename fs/namei.c:6099 [inline]
 __se_sys_rename fs/namei.c:6097 [inline]
 __x64_sys_rename+0x82/0x90 fs/namei.c:6097
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbac488f749
RSP: 002b:00007fbac2acd038 EFLAGS: 00000246 ORIG_RAX: 0000000000000052
RAX: ffffffffffffffda RBX: 00007fbac4ae6090 RCX: 00007fbac488f749
RDX: 0000000000000000 RSI: 00002000000002c0 RDI: 0000200000000580
RBP: 00007fbac4913f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbac4ae6128 R14: 00007fbac4ae6090 R15: 00007ffe0c5ccee8
 </TASK>
INFO: task syz.6.1413:18172 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.6.1413      state:D stack:26872 pid:18172 tgid:18143 ppid:15562  task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x145f/0x5070 kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 rt_mutex_schedule+0x77/0xf0 kernel/sched/core.c:7241
 rt_mutex_slowlock_block kernel/locking/rtmutex.c:1647 [inline]
 __rt_mutex_slowlock kernel/locking/rtmutex.c:1721 [inline]
 __rt_mutex_slowlock_locked+0x1dfe/0x25e0 kernel/locking/rtmutex.c:1760
 rt_mutex_slowlock+0xb5/0x160 kernel/locking/rtmutex.c:1800
 __rt_mutex_lock kernel/locking/rtmutex.c:1815 [inline]
 rwbase_write_lock+0x14f/0x750 kernel/locking/rwbase_rt.c:244
 inode_lock include/linux/fs.h:1027 [inline]
 open_last_lookups fs/namei.c:4546 [inline]
 path_openat+0xb53/0x3df0 fs/namei.c:4793
 do_filp_open+0x1fa/0x410 fs/namei.c:4823
 do_sys_openat2+0x121/0x200 fs/open.c:1430
 do_sys_open fs/open.c:1436 [inline]
 __do_sys_openat fs/open.c:1452 [inline]
 __se_sys_openat fs/open.c:1447 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1447
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbac488f749
RSP: 002b:00007fbac2aac038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fbac4ae6180 RCX: 00007fbac488f749
RDX: 0000000000101042 RSI: 0000200000000040 RDI: ffffffffffffff9c
RBP: 00007fbac4913f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000015 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbac4ae6218 R14: 00007fbac4ae6180 R15: 00007ffe0c5ccee8
 </TASK>
INFO: task syz.6.1413:18173 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.6.1413      state:D stack:28952 pid:18173 tgid:18143 ppid:15562  task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x145f/0x5070 kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 rt_mutex_schedule+0x77/0xf0 kernel/sched/core.c:7241
 rt_mutex_slowlock_block kernel/locking/rtmutex.c:1647 [inline]
 __rt_mutex_slowlock kernel/locking/rtmutex.c:1721 [inline]
 __rt_mutex_slowlock_locked+0x1dfe/0x25e0 kernel/locking/rtmutex.c:1760
 rt_mutex_slowlock+0xb5/0x160 kernel/locking/rtmutex.c:1800
 __rt_mutex_lock kernel/locking/rtmutex.c:1815 [inline]
 rwbase_write_lock+0x14f/0x750 kernel/locking/rwbase_rt.c:244
 inode_lock_nested include/linux/fs.h:1072 [inline]
 __start_dirop fs/namei.c:2873 [inline]
 start_dirop fs/namei.c:2884 [inline]
 do_unlinkat+0x1b2/0x570 fs/namei.c:5429
 __do_sys_unlink fs/namei.c:5483 [inline]
 __se_sys_unlink fs/namei.c:5481 [inline]
 __x64_sys_unlink+0x47/0x50 fs/namei.c:5481
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbac488f749
RSP: 002b:00007fbac2689038 EFLAGS: 00000246 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 00007fbac4ae6270 RCX: 00007fbac488f749
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000280
RBP: 00007fbac4913f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbac4ae6308 R14: 00007fbac4ae6270 R15: 00007ffe0c5ccee8
 </TASK>

Showing all locks held in the system:
4 locks held by pr/legacy/17:
1 lock held by khungtaskd/38:
 #0: ffffffff8d5ae940 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8d5ae940 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
 #0: ffffffff8d5ae940 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
2 locks held by getty/5556:
 #0: ffff88814e5a50a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90003e8b2e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x44f/0x1460 drivers/tty/n_tty.c:2211
4 locks held by kworker/u8:18/6168:
 #0: ffff888141291138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3232 [inline]
 #0: ffff888141291138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x1770 kernel/workqueue.c:3340
 #1: ffffc9000bf47bc0 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3233 [inline]
 #1: ffffc9000bf47bc0 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x1770 kernel/workqueue.c:3340
 #2: ffff8880974f00d0 (&type->s_umount_key#109){++++}-{4:4}, at: super_trylock_shared+0x20/0xf0 fs/super.c:563
 #3: ffff8880666828e8 (&jfs_ip->commit_mutex){+.+.}-{4:4}, at: jfs_commit_inode+0x1ca/0x530 fs/jfs/inode.c:108
1 lock held by syz-executor/15791:
4 locks held by syz.6.1413/18145:
2 locks held by syz.6.1413/18170:
 #0: ffff8880974f0480 (sb_writers#24){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:499
 #1: ffff888066682cb8 (&type->i_mutex_dir_key#19/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1072 [inline]
 #1: ffff888066682cb8 (&type->i_mutex_dir_key#19/1){+.+.}-{4:4}, at: lock_rename fs/namei.c:3721 [inline]
 #1: ffff888066682cb8 (&type->i_mutex_dir_key#19/1){+.+.}-{4:4}, at: __start_renaming+0x148/0x410 fs/namei.c:3817
2 locks held by syz.6.1413/18172:
 #0: ffff8880974f0480 (sb_writers#24){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:499
 #1: ffff888066682cb8 (&type->i_mutex_dir_key#20){++++}-{4:4}, at: inode_lock include/linux/fs.h:1027 [inline]
 #1: ffff888066682cb8 (&type->i_mutex_dir_key#20){++++}-{4:4}, at: open_last_lookups fs/namei.c:4546 [inline]
 #1: ffff888066682cb8 (&type->i_mutex_dir_key#20){++++}-{4:4}, at: path_openat+0xb53/0x3df0 fs/namei.c:4793
2 locks held by syz.6.1413/18173:
 #0: ffff8880974f0480 (sb_writers#24){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:499
 #1: ffff888066682cb8 (&type->i_mutex_dir_key#19/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1072 [inline]
 #1: ffff888066682cb8 (&type->i_mutex_dir_key#19/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2873 [inline]
 #1: ffff888066682cb8 (&type->i_mutex_dir_key#19/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2884 [inline]
 #1: ffff888066682cb8 (&type->i_mutex_dir_key#19/1){+.+.}-{4:4}, at: do_unlinkat+0x1b2/0x570 fs/namei.c:5429
4 locks held by udevd/19988:
5 locks held by syz.2.1654/20150:
4 locks held by syz.5.1660/20159:
3 locks held by syz.9.1657/20160:
3 locks held by syz.8.1659/20164:
1 lock held by cmp/20182:

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

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 10/25/2025
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:160 [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+0xf95/0xfe0 kernel/hung_task.c:515
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 17 Comm: pr/legacy Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:io_serial_in+0x77/0xc0 drivers/tty/serial/8250/8250_port.c:400
Code: e8 3e da b5 fc 44 89 f9 d3 e3 49 83 ee 80 4c 89 f0 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 af 13 18 fd 41 03 1e 89 da ec <0f> b6 c0 5b 41 5c 41 5e 41 5f c3 cc cc cc cc cc 44 89 f9 80 e1 07
RSP: 0018:ffffc90000167950 EFLAGS: 00000202
RAX: 1ffffffff31f3700 RBX: 00000000000003fd RCX: 0000000000000000
RDX: 00000000000003fd RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffffff98f9c010 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffffff8509d220 R12: dffffc0000000000
R13: 0000000000000000 R14: ffffffff98f9bd80 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff888126cee000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd9943fe000 CR3: 000000000d3a8000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 serial_in drivers/tty/serial/8250/8250.h:128 [inline]
 serial_lsr_in drivers/tty/serial/8250/8250.h:150 [inline]
 wait_for_lsr+0x1aa/0x2f0 drivers/tty/serial/8250/8250_port.c:1961
 fifo_wait_for_lsr drivers/tty/serial/8250/8250_port.c:3234 [inline]
 serial8250_console_fifo_write drivers/tty/serial/8250/8250_port.c:3257 [inline]
 serial8250_console_write+0x11bd/0x1b40 drivers/tty/serial/8250/8250_port.c:3342
 console_emit_next_record kernel/printk/printk.c:3109 [inline]
 console_flush_one_record+0x685/0xb80 kernel/printk/printk.c:3215
 legacy_kthread_func+0x16f/0x210 kernel/printk/printk.c:3674
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>