[syzbot] possible deadlock in console_unlock (2)

syzbot
2021-11-14T09:47:09Z

Hello,

syzbot found the following issue on:

HEAD commit: f2e19fd15bd7 Add linux-next specific files for 20211112
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=116e8501b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=ba9c83199208e103
dashboard link: https://syzkaller.appspot.com/bug?extid=0b7c8bfd17c00d016fb4
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17f041f1b00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1585cd76b00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0b7c8bfd17c00d016fb4@syzkaller.appspotmail.com

FAULT_INJECTION: forcing a failure.
name failslab, interval 1, probability 0, space 0, times 1
======================================================
WARNING: possible circular locking dependency detected
5.15.0-next-20211112-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor376/6515 is trying to acquire lock:
ffffffff8ba92c80 (console_owner){....}-{0:0}, at: console_unlock+0x303/0xb70 kernel/printk/printk.c:2710

but task is already holding lock:
ffff888078adf158 (&port->lock){-.-.}-{2:2}, at: pty_write+0xea/0x1e0 drivers/tty/pty.c:120

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (&port->lock){-.-.}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:162
tty_port_tty_get+0x1f/0x100 drivers/tty/tty_port.c:289
tty_port_default_wakeup+0x11/0x40 drivers/tty/tty_port.c:48
serial8250_tx_chars+0x4f3/0xad0 drivers/tty/serial/8250/8250_port.c:1845
serial8250_handle_irq.part.0+0x328/0x3d0 drivers/tty/serial/8250/8250_port.c:1932
serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1905 [inline]
serial8250_default_handle_irq+0xb2/0x220 drivers/tty/serial/8250/8250_port.c:1949
serial8250_interrupt+0xfd/0x200 drivers/tty/serial/8250/8250_core.c:126
__handle_irq_event_percpu+0x303/0x8f0 kernel/irq/handle.c:158
handle_irq_event_percpu kernel/irq/handle.c:198 [inline]
handle_irq_event+0x102/0x280 kernel/irq/handle.c:215
handle_edge_irq+0x25f/0xd00 kernel/irq/chip.c:822
generic_handle_irq_desc include/linux/irqdesc.h:158 [inline]
handle_irq arch/x86/kernel/irq.c:231 [inline]
__common_interrupt+0x9d/0x210 arch/x86/kernel/irq.c:250
common_interrupt+0xa4/0xc0 arch/x86/kernel/irq.c:240
asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:629
native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
acpi_safe_halt drivers/acpi/processor_idle.c:109 [inline]
acpi_idle_do_entry+0x1c6/0x250 drivers/acpi/processor_idle.c:553
acpi_idle_enter+0x361/0x500 drivers/acpi/processor_idle.c:688
cpuidle_enter_state+0x1b1/0xc80 drivers/cpuidle/cpuidle.c:237
cpuidle_enter+0x4a/0xa0 drivers/cpuidle/cpuidle.c:351
call_cpuidle kernel/sched/idle.c:158 [inline]
cpuidle_idle_call kernel/sched/idle.c:239 [inline]
do_idle+0x3e8/0x590 kernel/sched/idle.c:306
cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:403
start_kernel+0x47a/0x49b init/main.c:1141
secondary_startup_64_no_verify+0xb0/0xbb

-> #1 (&port_lock_key){-.-.}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:162
serial8250_console_write+0x91a/0xb70 drivers/tty/serial/8250/8250_port.c:3358
call_console_drivers kernel/printk/printk.c:1932 [inline]
console_unlock+0x7a9/0xb70 kernel/printk/printk.c:2714
vprintk_emit+0x198/0x4f0 kernel/printk/printk.c:2248
vprintk+0x80/0x90 kernel/printk/printk_safe.c:50
_printk+0xba/0xed kernel/printk/printk.c:2269
register_console kernel/printk/printk.c:3054 [inline]
register_console+0x55f/0x780 kernel/printk/printk.c:2934
univ8250_console_init+0x3a/0x46 drivers/tty/serial/8250/8250_core.c:680
console_init+0x3c1/0x58d kernel/printk/printk.c:3154
start_kernel+0x30b/0x49b init/main.c:1070
secondary_startup_64_no_verify+0xb0/0xbb

-> #0 (console_owner){....}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3063 [inline]
check_prevs_add kernel/locking/lockdep.c:3186 [inline]
validate_chain kernel/locking/lockdep.c:3801 [inline]
__lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5027
lock_acquire kernel/locking/lockdep.c:5637 [inline]
lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5602
console_lock_spinning_enable kernel/printk/printk.c:1784 [inline]
console_unlock+0x356/0xb70 kernel/printk/printk.c:2711
vprintk_emit+0x198/0x4f0 kernel/printk/printk.c:2248
vprintk+0x80/0x90 kernel/printk/printk_safe.c:50
_printk+0xba/0xed kernel/printk/printk.c:2269
fail_dump lib/fault-inject.c:45 [inline]
should_fail+0x472/0x5a0 lib/fault-inject.c:146
should_failslab+0x5/0x10 mm/slab_common.c:1320
slab_pre_alloc_hook mm/slab.h:494 [inline]
slab_alloc_node mm/slub.c:3148 [inline]
slab_alloc mm/slub.c:3242 [inline]
__kmalloc+0x72/0x340 mm/slub.c:4419
kmalloc include/linux/slab.h:595 [inline]
tty_buffer_alloc+0x23f/0x2a0 drivers/tty/tty_buffer.c:177
__tty_buffer_request_room+0x156/0x2a0 drivers/tty/tty_buffer.c:275
tty_insert_flip_string_fixed_flag+0x93/0x250 drivers/tty/tty_buffer.c:321
tty_insert_flip_string include/linux/tty_flip.h:42 [inline]
pty_write+0x11c/0x1e0 drivers/tty/pty.c:122
n_tty_write+0xa7a/0xfd0 drivers/tty/n_tty.c:2311
do_tty_write drivers/tty/tty_io.c:1038 [inline]
file_tty_write.constprop.0+0x526/0x910 drivers/tty/tty_io.c:1110
call_write_iter include/linux/fs.h:2162 [inline]
new_sync_write+0x429/0x660 fs/read_write.c:503
vfs_write+0x7cd/0xae0 fs/read_write.c:590
ksys_write+0x12d/0x250 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

other info that might help us debug this:

Chain exists of:
console_owner --> &port_lock_key --> &port->lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&port->lock);
lock(&port_lock_key);
lock(&port->lock);
lock(console_owner);

*** DEADLOCK ***

6 locks held by syz-executor376/6515:
#0: ffff88807e57e098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:252
#1: ffff88807e57e130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: tty_write_lock drivers/tty/tty_io.c:961 [inline]
#1: ffff88807e57e130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: do_tty_write drivers/tty/tty_io.c:984 [inline]
#1: ffff88807e57e130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: file_tty_write.constprop.0+0x29f/0x910 drivers/tty/tty_io.c:1110
#2: ffff88807e57e2e8 (&tty->termios_rwsem){++++}-{3:3}, at: n_tty_write+0x1bf/0xfd0 drivers/tty/n_tty.c:2271
#3: ffffc90001a78378 (&ldata->output_lock){+.+.}-{3:3}, at: n_tty_write+0xa47/0xfd0 drivers/tty/n_tty.c:2310
#4: ffff888078adf158 (&port->lock){-.-.}-{2:2}, at: pty_write+0xea/0x1e0 drivers/tty/pty.c:120
#5: ffffffff8bb730c0 (console_lock){+.+.}-{0:0}, at: vprintk+0x80/0x90 kernel/printk/printk_safe.c:50

stack backtrace:
CPU: 1 PID: 6515 Comm: syz-executor376 Not tainted 5.15.0-next-20211112-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2143
check_prev_add kernel/locking/lockdep.c:3063 [inline]
check_prevs_add kernel/locking/lockdep.c:3186 [inline]
validate_chain kernel/locking/lockdep.c:3801 [inline]
__lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5027
lock_acquire kernel/locking/lockdep.c:5637 [inline]
lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5602
console_lock_spinning_enable kernel/printk/printk.c:1784 [inline]
console_unlock+0x356/0xb70 kernel/printk/printk.c:2711
vprintk_emit+0x198/0x4f0 kernel/printk/printk.c:2248
vprintk+0x80/0x90 kernel/printk/printk_safe.c:50
_printk+0xba/0xed kernel/printk/printk.c:2269
fail_dump lib/fault-inject.c:45 [inline]
should_fail+0x472/0x5a0 lib/fault-inject.c:146
should_failslab+0x5/0x10 mm/slab_common.c:1320
slab_pre_alloc_hook mm/slab.h:494 [inline]
slab_alloc_node mm/slub.c:3148 [inline]
slab_alloc mm/slub.c:3242 [inline]
__kmalloc+0x72/0x340 mm/slub.c:4419
kmalloc include/linux/slab.h:595 [inline]
tty_buffer_alloc+0x23f/0x2a0 drivers/tty/tty_buffer.c:177
__tty_buffer_request_room+0x156/0x2a0 drivers/tty/tty_buffer.c:275
tty_insert_flip_string_fixed_flag+0x93/0x250 drivers/tty/tty_buffer.c:321
tty_insert_flip_string include/linux/tty_flip.h:42 [inline]
pty_write+0x11c/0x1e0 drivers/tty/pty.c:122
n_tty_write+0xa7a/0xfd0 drivers/tty/n_tty.c:2311
do_tty_write drivers/tty/tty_io.c:1038 [inline]
file_tty_write.constprop.0+0x526/0x910 drivers/tty/tty_io.c:1110
call_write_iter include/linux/fs.h:2162 [inline]
new_sync_write+0x429/0x660 fs/read_write.c:503
vfs_write+0x7cd/0xae0 fs/read_write.c:590
ksys_write+0x12d/0x250 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f41ad8ca679
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 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 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffed0e96e38 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f41ad8ca679
RDX: 000000000000ff2e RSI: 0000000020000180 RDI: 0000000000000003
RBP: 00007ffed0e96e40 R08: 0000000000000001 R09: 00007f41ad880033
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
CPU: 1 PID: 6515 Comm: syz-executor376 Not tainted 5.15.0-next-20211112-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
fail_dump lib/fault-inject.c:52 [inline]
should_fail.cold+0x5/0xa lib/fault-inject.c:146
should_failslab+0x5/0x10 mm/slab_common.c:1320
slab_pre_alloc_hook mm/slab.h:494 [inline]
slab_alloc_node mm/slub.c:3148 [inline]
slab_alloc mm/slub.c:3242 [inline]
__kmalloc+0x72/0x340 mm/slub.c:4419
kmalloc include/linux/slab.h:595 [inline]
tty_buffer_alloc+0x23f/0x2a0 drivers/tty/tty_buffer.c:177
__tty_buffer_request_room+0x156/0x2a0 drivers/tty/tty_buffer.c:275
tty_insert_flip_string_fixed_flag+0x93/0x250 drivers/tty/tty_buffer.c:321
tty_insert_flip_string include/linux/tty_flip.h:42 [inline]
pty_write+0x11c/0x1e0 drivers/tty/pty.c:122
n_tty_write+0xa7a/0xfd0 drivers/tty/n_tty.c:2311
do_tty_write drivers/tty/tty_io.c:1038 [inline]
file_tty_write.constprop.0+0x526/0x910 drivers/tty/tty_io.c:1110
call_write_iter include/linux/fs.h:2162 [inline]
new_sync_write+0x429/0x660 fs/read_write.c:503
vfs_write+0x7cd/0xae0 fs/read_write.c:590
ksys_write+0x12d/0x250 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f41ad8ca679
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 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 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffed0e96e38 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f41ad8ca679
RDX: 000000000000ff2e RSI: 0000000020000180 RDI: 0000000000000003
RBP: 00007ffed0e96e40 R08: 0000000000000001 R09: 00007f41ad880033
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>

---
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