INFO: task syz.3.5389:20870 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.5389 state:D stack:28920 pid:20870 tgid:20867 ppid:15300 task_flags:0x400140 flags:0x00080002
Call Trace:
context_switch kernel/sched/core.c:5402 [inline]
__schedule+0x16f9/0x5500 kernel/sched/core.c:7204
__schedule_loop kernel/sched/core.c:7283 [inline]
rt_mutex_schedule+0x76/0xf0 kernel/sched/core.c:7579
rt_mutex_slowlock_block+0x508/0x680 kernel/locking/rtmutex.c:1666
__rt_mutex_slowlock kernel/locking/rtmutex.c:1743 [inline]
__rt_mutex_slowlock_locked kernel/locking/rtmutex.c:1783 [inline]
rt_mutex_slowlock+0x2dc/0x780 kernel/locking/rtmutex.c:1823
__rt_mutex_lock kernel/locking/rtmutex.c:1838 [inline]
__mutex_lock_common kernel/locking/rtmutex_api.c:560 [inline]
mutex_lock_nested+0x168/0x1d0 kernel/locking/rtmutex_api.c:578
epoll_mutex_lock fs/eventpoll.c:2512 [inline]
ep_ctl_lock fs/eventpoll.c:2559 [inline]
do_epoll_ctl_file+0x9d1/0xed0 fs/eventpoll.c:2636
do_epoll_ctl fs/eventpoll.c:2698 [inline]
__do_sys_epoll_ctl fs/eventpoll.c:2715 [inline]
__se_sys_epoll_ctl+0x14e/0x210 fs/eventpoll.c:2706
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: 0033:0x7f015624ce59
RSP: 002b:00007f015449e028 EFLAGS: 00000246 ORIG_RAX: 00000000000000e9
RAX: ffffffffffffffda RBX: 00007f01564c5fa0 RCX: 00007f015624ce59
RDX: 0000000000000003 RSI: 0000000000000001 RDI: 0000000000000005
RBP: 00007f01562e2d6f R08: 0000000000000000 R09: 0000000000000000
R10: 00002000000002c0 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f01564c6038 R14: 00007f01564c5fa0 R15: 00007ffdd967a6f8
Showing all locks held in the system:
4 locks held by pr/legacy/17:
#0: ffffffff8e1bcf40 (console_lock){+.+.}-{0:0}, at: legacy_kthread_func+0x1a3/0x250 kernel/printk/printk.c:3711
#1: ffffffff8e0a4838 (console_srcu){....}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:305 [inline]
#1: ffffffff8e0a4838 (console_srcu){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:428 [inline]
#1: ffffffff8e0a4838 (console_srcu){....}-{0:0}, at: console_srcu_read_lock kernel/printk/printk.c:291 [inline]
#1: ffffffff8e0a4838 (console_srcu){....}-{0:0}, at: console_flush_one_record+0xfa/0xb90 kernel/printk/printk.c:3246
#2: ffffffff99e02fd8 (&port_lock_key){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
#2: ffffffff99e02fd8 (&port_lock_key){+.+.}-{3:3}, at: uart_port_lock_irqsave include/linux/serial_core.h:719 [inline]
#2: ffffffff99e02fd8 (&port_lock_key){+.+.}-{3:3}, at: serial8250_console_write+0x179/0x1b90 drivers/tty/serial/8250/8250_port.c:3321
#3: ffffffff8e1cacc0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#3: ffffffff8e1cacc0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
#3: ffffffff8e1cacc0 (rcu_read_lock){....}-{1:3}, at: __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline]
#3: ffffffff8e1cacc0 (rcu_read_lock){....}-{1:3}, at: rt_spin_lock+0x1e0/0x400 kernel/locking/spinlock_rt.c:57
1 lock held by khungtaskd/39:
#0: ffffffff8e1cacc0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#0: ffffffff8e1cacc0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
#0: ffffffff8e1cacc0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6777
2 locks held by getty/5376:
#0: ffff888032ac90a0 (&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+0x462/0x13a0 drivers/tty/n_tty.c:2211
2 locks held by syz.3.914/8010:
#0: ffffffff8e3579d8 (epnested_mutex){+.+.}-{4:4}, at: epoll_mutex_lock fs/eventpoll.c:2512 [inline]
#0: ffffffff8e3579d8 (epnested_mutex){+.+.}-{4:4}, at: ep_ctl_lock fs/eventpoll.c:2559 [inline]
#0: ffffffff8e3579d8 (epnested_mutex){+.+.}-{4:4}, at: do_epoll_ctl_file+0x9d1/0xed0 fs/eventpoll.c:2636
#1: ffff88802b11f058 (&ep->mtx){+.+.}-{4:4}, at: epoll_mutex_lock fs/eventpoll.c:2512 [inline]
#1: ffff88802b11f058 (&ep->mtx){+.+.}-{4:4}, at: ep_ctl_lock fs/eventpoll.c:2573 [inline]
#1: ffff88802b11f058 (&ep->mtx){+.+.}-{4:4}, at: do_epoll_ctl_file+0xc69/0xed0 fs/eventpoll.c:2636
1 lock held by syz.3.5389/20870:
#0: ffffffff8e3579d8 (epnested_mutex){+.+.}-{4:4}, at: epoll_mutex_lock fs/eventpoll.c:2512 [inline]
#0: ffffffff8e3579d8 (epnested_mutex){+.+.}-{4:4}, at: ep_ctl_lock fs/eventpoll.c:2559 [inline]
#0: ffffffff8e3579d8 (epnested_mutex){+.+.}-{4:4}, at: do_epoll_ctl_file+0x9d1/0xed0 fs/eventpoll.c:2636
1 lock held by syz.5.6001/22725:
#0: ffff88803d9e87f0 (&u->iolock){+.+.}-{4:4}, at: __unix_dgram_recvmsg+0x1e2/0xd60 net/unix/af_unix.c:2584
2 locks held by syz.4.6002/22718:
#0: ffff888038311558 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline]
#0: ffff888038311558 (sk_lock-AF_INET){+.+.}-{0:0}, at: l2tp_ip_sendmsg+0x34/0x1620 net/l2tp/l2tp_ip.c:433
#1: ffffffff8e061640 (local_bh){.+.+}-{1:3}, at: __local_bh_disable_ip+0x3c/0x420 kernel/softirq.c:163
1 lock held by syz.9.6004/22721:
#0: ffff88805c263a30 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock_killable include/linux/mmap_lock.h:554 [inline]
#0: ffff88805c263a30 (&mm->mmap_lock){++++}-{4:4}, at: vm_mmap_pgoff+0x237/0x4f0 mm/util.c:579
2 locks held by syz.9.6004/22724:
#0: ffff88805c263a30 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock include/linux/mmap_lock.h:592 [inline]
#0: ffff88805c263a30 (&mm->mmap_lock){++++}-{4:4}, at: __mm_populate+0x182/0x390 mm/gup.c:1942
#1: ffffffff8e1cacc0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#1: ffffffff8e1cacc0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
#1: ffffffff8e1cacc0 (rcu_read_lock){....}-{1:3}, at: class_rcu_constructor include/linux/rcupdate.h:1181 [inline]
#1: ffffffff8e1cacc0 (rcu_read_lock){....}-{1:3}, at: unwind_next_frame+0xa6/0x2550 arch/x86/kernel/unwind_orc.c:495
=============================================
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 39 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
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+0xfd3/0x1030 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
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 04/18/2026
RIP: 0010:io_serial_in+0x77/0xc0 drivers/tty/serial/8250/8250_port.c:401
Code: e8 8e aa 7a 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 6f 41 e5 fc 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:ffffc900001679d0 EFLAGS: 00000202
RAX: 1ffffffff33c0600 RBX: 00000000000003fd RCX: 0000000000000000
RDX: 00000000000003fd RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffffff99e03290 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffffff854b0c20 R12: dffffc0000000000
R13: 0000000000000000 R14: ffffffff99e03000 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff888125c8b000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f07457edd58 CR3: 0000000039ee2000 CR4: 00000000003526f0
DR0: 0000000000000008 DR1: 0000000000000007 DR2: 0000000000000004
DR3: 0000000000000008 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
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:1975
serial8250_fifo_wait_for_lsr_thre drivers/tty/serial/8250/8250_port.c:3212 [inline]
serial8250_console_fifo_write drivers/tty/serial/8250/8250_port.c:3277 [inline]
serial8250_console_write+0x11c9/0x1b90 drivers/tty/serial/8250/8250_port.c:3362
console_emit_next_record kernel/printk/printk.c:3163 [inline]
console_flush_one_record+0x68b/0xb90 kernel/printk/printk.c:3269
legacy_kthread_func+0x1b6/0x250 kernel/printk/printk.c:3712
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