======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.4.467/6389 is trying to acquire lock:
ffff88807a446558 (&ep->lock){-...}-{2:2}, at: ep_poll_callback+0x78/0x9e0 fs/eventpoll.c:1093
but task is already holding lock:
ffff88807a322528 (&tty->write_wait){-.-.}-{2:2}, at: __wake_up_common_lock kernel/sched/wait.c:137 [inline]
ffff88807a322528 (&tty->write_wait){-.-.}-{2:2}, at: __wake_up+0xf4/0x190 kernel/sched/wait.c:160
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #6 (&tty->write_wait){-.-.}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162
__wake_up_common_lock kernel/sched/wait.c:137 [inline]
__wake_up+0xf4/0x190 kernel/sched/wait.c:160
tty_port_default_wakeup+0x9e/0xf0 drivers/tty/tty_port.c:71
serial8250_tx_chars+0x629/0x830 drivers/tty/serial/8250/8250_port.c:1854
serial8250_handle_irq+0x516/0x6d0 drivers/tty/serial/8250/8250_port.c:1961
serial8250_default_handle_irq+0xb4/0x1a0 drivers/tty/serial/8250/8250_port.c:1981
serial8250_interrupt+0x9b/0x1c0 drivers/tty/serial/8250/8250_core.c:126
__handle_irq_event_percpu+0x298/0xa30 kernel/irq/handle.c:158
handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
handle_irq_event+0x87/0x1e0 kernel/irq/handle.c:210
handle_edge_irq+0x243/0xb20 kernel/irq/chip.c:819
generic_handle_irq_desc include/linux/irqdesc.h:158 [inline]
handle_irq arch/x86/kernel/irq.c:233 [inline]
__common_interrupt+0xd7/0x1e0 arch/x86/kernel/irq.c:252
common_interrupt+0xb0/0xd0 arch/x86/kernel/irq.c:242
asm_common_interrupt+0x22/0x40 arch/x86/include/asm/idtentry.h:682
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
_raw_spin_unlock_irqrestore+0xa5/0x100 kernel/locking/spinlock.c:194
spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
uart_write+0x68a/0x910 drivers/tty/serial/serial_core.c:602
process_output_block drivers/tty/n_tty.c:586 [inline]
n_tty_write+0xd1a/0x11c0 drivers/tty/n_tty.c:2377
do_tty_write drivers/tty/tty_io.c:1018 [inline]
file_tty_write+0x4dd/0x860 drivers/tty/tty_io.c:1089
call_write_iter include/linux/fs.h:2265 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x44c/0x960 fs/read_write.c:584
ksys_write+0x143/0x240 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
-> #5 (&port_lock_key){-.-.}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162
serial8250_console_write+0x169/0x17a0 drivers/tty/serial/8250/8250_port.c:3432
call_console_driver kernel/printk/printk.c:1977 [inline]
console_emit_next_record+0x947/0xc90 kernel/printk/printk.c:2777
console_flush_all kernel/printk/printk.c:-1 [inline]
console_unlock+0x223/0x630 kernel/printk/printk.c:2906
vprintk_emit+0x489/0x680 kernel/printk/printk.c:2303
_printk+0xcc/0x110 kernel/printk/printk.c:2328
register_console+0x6c6/0x9c0 kernel/printk/printk.c:3269
univ8250_console_init+0x41/0x43 drivers/tty/serial/8250/8250_core.c:687
console_init+0x1bc/0x78e kernel/printk/printk.c:3359
start_kernel+0x303/0x539 init/main.c:1088
secondary_startup_64_no_verify+0xcf/0xdb
-> #4 (console_owner){-.-.}-{0:0}:
console_lock_spinning_enable kernel/printk/printk.c:1818 [inline]
console_emit_next_record+0x84c/0xc90 kernel/printk/printk.c:2774
console_flush_all kernel/printk/printk.c:-1 [inline]
console_unlock+0x223/0x630 kernel/printk/printk.c:2906
vprintk_emit+0x489/0x680 kernel/printk/printk.c:2303
_printk+0xcc/0x110 kernel/printk/printk.c:2328
fail_dump lib/fault-inject.c:45 [inline]
should_fail_ex+0x37a/0x4d0 lib/fault-inject.c:147
strncpy_from_user+0x32/0x350 lib/strncpy_from_user.c:118
strncpy_from_user_nofault+0x6d/0x140 mm/maccess.c:186
bpf_trace_copy_string kernel/bpf/helpers.c:746 [inline]
bpf_bprintf_prepare+0xba0/0x13d0 kernel/bpf/helpers.c:971
____bpf_trace_printk kernel/trace/bpf_trace.c:384 [inline]
bpf_trace_printk+0xd8/0x190 kernel/trace/bpf_trace.c:374
0xffffffffa0000991
bpf_dispatcher_nop_func include/linux/bpf.h:1012 [inline]
__bpf_prog_run include/linux/filter.h:607 [inline]
bpf_prog_run include/linux/filter.h:614 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2285 [inline]
bpf_trace_run2+0x1cd/0x3d0 kernel/trace/bpf_trace.c:2324
trace_contention_begin+0x142/0x190 include/trace/events/lock.h:95
__pv_queued_spin_lock_slowpath+0xdc/0x9c0 kernel/locking/qspinlock.c:405
pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:591 [inline]
queued_spin_lock_slowpath+0x43/0x50 arch/x86/include/asm/qspinlock.h:51
queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
do_raw_spin_lock+0x217/0x280 kernel/locking/spinlock_debug.c:115
raw_spin_rq_lock_nested+0xa5/0x140 kernel/sched/core.c:546
raw_spin_rq_lock kernel/sched/sched.h:1362 [inline]
rq_lock kernel/sched/sched.h:1652 [inline]
__schedule+0x2ed/0x40b0 kernel/sched/core.c:6478
preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6874
irqentry_exit+0x63/0x70 kernel/entry/common.c:439
asm_sysvec_reschedule_ipi+0x16/0x20 arch/x86/include/asm/idtentry.h:696
lockdep_init_map_type+0xb0/0x880 kernel/locking/lockdep.c:4813
__init_waitqueue_head+0xa5/0x150 kernel/sched/wait.c:11
alloc_pipe_info+0x267/0x4b0 fs/pipe.c:817
splice_direct_to_actor+0x91f/0xb60 fs/splice.c:841
do_splice_direct+0x1b0/0x2b0 fs/splice.c:1002
do_sendfile+0x5cc/0xeb0 fs/read_write.c:1255
__do_sys_sendfile64 fs/read_write.c:1317 [inline]
__se_sys_sendfile64+0xd6/0x190 fs/read_write.c:1309
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
-> #3 (&rq->__lock){-.-.}-{2:2}:
_raw_spin_lock_nested+0x2e/0x40 kernel/locking/spinlock.c:378
raw_spin_rq_lock_nested+0x26/0x140 kernel/sched/core.c:538
raw_spin_rq_lock kernel/sched/sched.h:1362 [inline]
rq_lock kernel/sched/sched.h:1652 [inline]
task_fork_fair+0x5c/0x350 kernel/sched/fair.c:11928
sched_cgroup_fork+0x32c/0x3c0 kernel/sched/core.c:4686
copy_process+0x24b8/0x4020 kernel/fork.c:2464
kernel_clone+0x225/0x8b0 kernel/fork.c:2762
user_mode_thread+0xda/0x130 kernel/fork.c:2838
rest_init+0x23/0x300 init/main.c:710
start_kernel+0x0/0x539 init/main.c:905
start_kernel+0x490/0x539 init/main.c:1152
secondary_startup_64_no_verify+0xcf/0xdb
-> #2 (&p->pi_lock){-.-.}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162
try_to_wake_up+0x5c/0x1080 kernel/sched/core.c:4112
ep_autoremove_wake_function+0x34/0x120 fs/eventpoll.c:1716
__wake_up_common+0x2a4/0x4e0 kernel/sched/wait.c:107
__wake_up_common_lock kernel/sched/wait.c:138 [inline]
__wake_up_sync_key kernel/sched/wait.c:208 [inline]
__wake_up_sync+0x106/0x180 kernel/sched/wait.c:240
ep_poll_callback+0x56e/0x9e0 fs/eventpoll.c:1155
__wake_up_common+0x2a4/0x4e0 kernel/sched/wait.c:107
__wake_up_common_lock kernel/sched/wait.c:138 [inline]
__wake_up_sync_key+0x10d/0x180 kernel/sched/wait.c:208
sock_def_readable+0x15b/0x280 net/core/sock.c:3316
__netlink_sendskb net/netlink/af_netlink.c:1264 [inline]
netlink_broadcast_deliver net/netlink/af_netlink.c:1399 [inline]
do_one_broadcast net/netlink/af_netlink.c:1479 [inline]
netlink_broadcast+0xcea/0x10d0 net/netlink/af_netlink.c:1519
uevent_net_broadcast_untagged lib/kobject_uevent.c:331 [inline]
kobject_uevent_net_broadcast+0x364/0x530 lib/kobject_uevent.c:409
kobject_uevent_env+0x54c/0x8a0 lib/kobject_uevent.c:608
kobject_synth_uevent+0x520/0xaf0 lib/kobject_uevent.c:208
bus_uevent_store+0x4c/0x70 drivers/base/bus.c:765
kernfs_fop_write_iter+0x3b2/0x520 fs/kernfs/file.c:352
call_write_iter include/linux/fs.h:2265 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x44c/0x960 fs/read_write.c:584
ksys_write+0x143/0x240 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
-> #1 (&ep->wq){....}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162
__wake_up_common_lock kernel/sched/wait.c:137 [inline]
__wake_up_sync_key kernel/sched/wait.c:208 [inline]
__wake_up_sync+0xeb/0x180 kernel/sched/wait.c:240
ep_poll_callback+0x56e/0x9e0 fs/eventpoll.c:1155
__wake_up_common+0x2a4/0x4e0 kernel/sched/wait.c:107
__wake_up_common_lock kernel/sched/wait.c:138 [inline]
__wake_up_sync_key+0x10d/0x180 kernel/sched/wait.c:208
sock_def_readable+0x15b/0x280 net/core/sock.c:3316
__netlink_sendskb net/netlink/af_netlink.c:1264 [inline]
netlink_broadcast_deliver net/netlink/af_netlink.c:1399 [inline]
do_one_broadcast net/netlink/af_netlink.c:1479 [inline]
netlink_broadcast+0xcea/0x10d0 net/netlink/af_netlink.c:1519
uevent_net_broadcast_untagged lib/kobject_uevent.c:331 [inline]
kobject_uevent_net_broadcast+0x364/0x530 lib/kobject_uevent.c:409
kobject_uevent_env+0x54c/0x8a0 lib/kobject_uevent.c:608
kobject_synth_uevent+0x520/0xaf0 lib/kobject_uevent.c:208
bus_uevent_store+0x4c/0x70 drivers/base/bus.c:765
kernfs_fop_write_iter+0x3b2/0x520 fs/kernfs/file.c:352
call_write_iter include/linux/fs.h:2265 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x44c/0x960 fs/read_write.c:584
ksys_write+0x143/0x240 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
-> #0 (&ep->lock){-...}-{2:2}:
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain kernel/locking/lockdep.c:3825 [inline]
__lock_acquire+0x2cf8/0x7c50 kernel/locking/lockdep.c:5049
lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162
ep_poll_callback+0x78/0x9e0 fs/eventpoll.c:1093
__wake_up_common+0x2a4/0x4e0 kernel/sched/wait.c:107
__wake_up_common_lock kernel/sched/wait.c:138 [inline]
__wake_up+0x10e/0x190 kernel/sched/wait.c:160
n_hdlc_send_frames+0x519/0xa30 drivers/tty/n_hdlc.c:307
n_hdlc_tty_write+0x711/0x870 drivers/tty/n_hdlc.c:568
do_tty_write drivers/tty/tty_io.c:1018 [inline]
file_tty_write+0x4dd/0x860 drivers/tty/tty_io.c:1089
do_iter_readv_writev fs/read_write.c:-1 [inline]
do_iter_write+0x62d/0xaf0 fs/read_write.c:861
vfs_writev fs/read_write.c:934 [inline]
do_writev+0x24e/0x410 fs/read_write.c:977
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
other info that might help us debug this:
Chain exists of:
&ep->lock --> &port_lock_key --> &tty->write_wait
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&tty->write_wait);
lock(&port_lock_key);
lock(&tty->write_wait);
lock(&ep->lock);
*** DEADLOCK ***
3 locks held by syz.4.467/6389:
#0: ffff88807a322098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
#1: ffff88807a322130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: tty_write_lock drivers/tty/tty_io.c:944 [inline]
#1: ffff88807a322130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: do_tty_write drivers/tty/tty_io.c:967 [inline]
#1: ffff88807a322130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: file_tty_write+0x1eb/0x860 drivers/tty/tty_io.c:1089
#2: ffff88807a322528 (&tty->write_wait){-.-.}-{2:2}, at: __wake_up_common_lock kernel/sched/wait.c:137 [inline]
#2: ffff88807a322528 (&tty->write_wait){-.-.}-{2:2}, at: __wake_up+0xf4/0x190 kernel/sched/wait.c:160
stack backtrace:
CPU: 1 PID: 6389 Comm: syz.4.467 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
check_noncircular+0x274/0x310 kernel/locking/lockdep.c:2170
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain kernel/locking/lockdep.c:3825 [inline]
__lock_acquire+0x2cf8/0x7c50 kernel/locking/lockdep.c:5049
lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162
ep_poll_callback+0x78/0x9e0 fs/eventpoll.c:1093
__wake_up_common+0x2a4/0x4e0 kernel/sched/wait.c:107
__wake_up_common_lock kernel/sched/wait.c:138 [inline]
__wake_up+0x10e/0x190 kernel/sched/wait.c:160
n_hdlc_send_frames+0x519/0xa30 drivers/tty/n_hdlc.c:307
n_hdlc_tty_write+0x711/0x870 drivers/tty/n_hdlc.c:568
do_tty_write drivers/tty/tty_io.c:1018 [inline]
file_tty_write+0x4dd/0x860 drivers/tty/tty_io.c:1089
do_iter_readv_writev fs/read_write.c:-1 [inline]
do_iter_write+0x62d/0xaf0 fs/read_write.c:861
vfs_writev fs/read_write.c:934 [inline]
do_writev+0x24e/0x410 fs/read_write.c:977
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f076338f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f076419d038 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007f07635e5fa0 RCX: 00007f076338f749
RDX: 0000000000000001 RSI: 0000200000000200 RDI: 0000000000000005
RBP: 00007f0763413f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f07635e6038 R14: 00007f07635e5fa0 R15: 00007fffa7695b88
</TASK>
loop4: detected capacity change from 0 to 64