WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dff9f829 Add linux-next specific files for 20200908
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=113184dd900000
kernel config: https://syzkaller.appspot.com/x/.config?x=37b3426c77bda44c
dashboard link: https://syzkaller.appspot.com/bug?extid=22e87cdf94021b984aa6
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=108b740d900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12daa9ed900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+22e87c...@syzkaller.appspotmail.com

netdevsim netdevsim0 netdevsim1: set [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim0 netdevsim2: set [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim0 netdevsim3: set [1, 0] type 2 family 0 port 6081 - 0
=====================================================
WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
5.9.0-rc4-next-20200908-syzkaller #0 Not tainted
-----------------------------------------------------
syz-executor198/6886 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
ffff88809ad60638 (&f->f_owner.lock){.+.+}-{2:2}, at: send_sigio+0x24/0x320 fs/fcntl.c:786

and this task is already holding:
ffff888092b709f0 (&new->fa_lock){....}-{2:2}, at: kill_fasync_rcu fs/fcntl.c:1002 [inline]
ffff888092b709f0 (&new->fa_lock){....}-{2:2}, at: kill_fasync fs/fcntl.c:1023 [inline]
ffff888092b709f0 (&new->fa_lock){....}-{2:2}, at: kill_fasync+0x14b/0x460 fs/fcntl.c:1016
which would create a new lock dependency:
(&new->fa_lock){....}-{2:2} -> (&f->f_owner.lock){.+.+}-{2:2}

but this new dependency connects a HARDIRQ-irq-safe lock:
(&dev->event_lock){-...}-{2:2}

... which became HARDIRQ-irq-safe at:
lock_acquire+0x1f3/0xaf0 kernel/locking/lockdep.c:5398
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x94/0xd0 kernel/locking/spinlock.c:159
input_event drivers/input/input.c:440 [inline]
input_event+0x7b/0xb0 drivers/input/input.c:433
input_report_key include/linux/input.h:417 [inline]
psmouse_report_standard_buttons+0x2c/0x80 drivers/input/mouse/psmouse-base.c:123
psmouse_report_standard_packet drivers/input/mouse/psmouse-base.c:141 [inline]
psmouse_process_byte+0x1e1/0x890 drivers/input/mouse/psmouse-base.c:232
psmouse_handle_byte+0x41/0x1b0 drivers/input/mouse/psmouse-base.c:274
psmouse_interrupt+0x2fa/0xe90 drivers/input/mouse/psmouse-base.c:426
serio_interrupt+0x88/0x150 drivers/input/serio/serio.c:1002
i8042_interrupt+0x270/0x500 drivers/input/serio/i8042.c:598
__handle_irq_event_percpu+0x223/0xaa0 kernel/irq/handle.c:156
handle_irq_event_percpu kernel/irq/handle.c:196 [inline]
handle_irq_event+0x102/0x290 kernel/irq/handle.c:213
handle_edge_irq+0x25f/0xd00 kernel/irq/chip.c:819
asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706
__run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
handle_irq arch/x86/kernel/irq.c:230 [inline]
__common_interrupt arch/x86/kernel/irq.c:249 [inline]
common_interrupt+0x115/0x1f0 arch/x86/kernel/irq.c:239
asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:572
arch_local_irq_restore arch/x86/include/asm/paravirt.h:653 [inline]
lock_acquire+0x27b/0xaf0 kernel/locking/lockdep.c:5401
rcu_lock_acquire include/linux/rcupdate.h:248 [inline]
rcu_read_lock include/linux/rcupdate.h:641 [inline]
path_init+0x851/0x13c0 fs/namei.c:2213
path_openat+0x185/0x2730 fs/namei.c:3364
do_filp_open+0x17e/0x3c0 fs/namei.c:3396
do_open_execat+0x116/0x690 fs/exec.c:910
bprm_execve+0x508/0x1b10 fs/exec.c:1909
kernel_execve+0x370/0x460 fs/exec.c:2080
call_usermodehelper_exec_async+0x27a/0x500 kernel/umh.c:101
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

to a HARDIRQ-irq-unsafe lock:
(&f->f_owner.lock){.+.+}-{2:2}

... which became HARDIRQ-irq-unsafe at:
...
lock_acquire+0x1f3/0xaf0 kernel/locking/lockdep.c:5398
__raw_read_lock include/linux/rwlock_api_smp.h:149 [inline]
_raw_read_lock+0x5b/0x70 kernel/locking/spinlock.c:223
send_sigurg+0x1e/0xa60 fs/fcntl.c:824
sk_send_sigurg+0x76/0x300 net/core/sock.c:2930
tcp_check_urg.isra.0+0x1f4/0x710 net/ipv4/tcp_input.c:5485
tcp_urg net/ipv4/tcp_input.c:5526 [inline]
tcp_rcv_established+0x10b9/0x1eb0 net/ipv4/tcp_input.c:5858
tcp_v4_do_rcv+0x5d1/0x870 net/ipv4/tcp_ipv4.c:1643
sk_backlog_rcv include/net/sock.h:1011 [inline]
__release_sock+0x134/0x3a0 net/core/sock.c:2528
release_sock+0x54/0x1b0 net/core/sock.c:3051
tcp_sendmsg+0x36/0x40 net/ipv4/tcp.c:1444
inet_sendmsg+0x99/0xe0 net/ipv4/af_inet.c:817
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:671
__sys_sendto+0x21c/0x320 net/socket.c:1992
__do_sys_sendto net/socket.c:2004 [inline]
__se_sys_sendto net/socket.c:2000 [inline]
__x64_sys_sendto+0xdd/0x1b0 net/socket.c:2000
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

other info that might help us debug this:

Chain exists of:
&dev->event_lock --> &new->fa_lock --> &f->f_owner.lock

Possible interrupt unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&f->f_owner.lock);
local_irq_disable();
lock(&dev->event_lock);
lock(&new->fa_lock);
<Interrupt>
lock(&dev->event_lock);

*** DEADLOCK ***

8 locks held by syz-executor198/6886:
#0: ffff88809d2b5160 (&evdev->mutex){+.+.}-{3:3}, at: evdev_write+0x1cd/0x750 drivers/input/evdev.c:513
#1: ffff88809eddc230 (&dev->event_lock){-...}-{2:2}, at: input_inject_event+0xa6/0x310 drivers/input/input.c:466
#2: ffffffff89c68540 (rcu_read_lock){....}-{1:2}, at: is_event_supported drivers/input/input.c:53 [inline]
#2: ffffffff89c68540 (rcu_read_lock){....}-{1:2}, at: is_event_supported drivers/input/input.c:50 [inline]
#2: ffffffff89c68540 (rcu_read_lock){....}-{1:2}, at: input_inject_event+0x92/0x310 drivers/input/input.c:465
#3: ffffffff89c68540 (rcu_read_lock){....}-{1:2}, at: input_pass_values.part.0+0x0/0x700 drivers/input/input.c:833
#4: ffffffff89c68540 (rcu_read_lock){....}-{1:2}, at: evdev_events+0x55/0x330 drivers/input/evdev.c:297
#5: ffff8880a81d4028 (&client->buffer_lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:354 [inline]
#5: ffff8880a81d4028 (&client->buffer_lock){....}-{2:2}, at: evdev_pass_values+0x195/0xa30 drivers/input/evdev.c:262
#6: ffffffff89c68540 (rcu_read_lock){....}-{1:2}, at: kill_fasync+0x3d/0x460 fs/fcntl.c:1021
#7: ffff888092b709f0 (&new->fa_lock){....}-{2:2}, at: kill_fasync_rcu fs/fcntl.c:1002 [inline]
#7: ffff888092b709f0 (&new->fa_lock){....}-{2:2}, at: kill_fasync fs/fcntl.c:1023 [inline]
#7: ffff888092b709f0 (&new->fa_lock){....}-{2:2}, at: kill_fasync+0x14b/0x460 fs/fcntl.c:1016

the dependencies between HARDIRQ-irq-safe lock and the holding lock:
-> (&dev->event_lock){-...}-{2:2} {
IN-HARDIRQ-W at:
lock_acquire+0x1f3/0xaf0 kernel/locking/lockdep.c:5398
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x94/0xd0 kernel/locking/spinlock.c:159
input_event drivers/input/input.c:440 [inline]
input_event+0x7b/0xb0 drivers/input/input.c:433
input_report_key include/linux/input.h:417 [inline]
psmouse_report_standard_buttons+0x2c/0x80 drivers/input/mouse/psmouse-base.c:123
psmouse_report_standard_packet drivers/input/mouse/psmouse-base.c:141 [inline]
psmouse_process_byte+0x1e1/0x890 drivers/input/mouse/psmouse-base.c:232
psmouse_handle_byte+0x41/0x1b0 drivers/input/mouse/psmouse-base.c:274
psmouse_interrupt+0x2fa/0xe90 drivers/input/mouse/psmouse-base.c:426
serio_interrupt+0x88/0x150 drivers/input/serio/serio.c:1002
i8042_interrupt+0x270/0x500 drivers/input/serio/i8042.c:598
__handle_irq_event_percpu+0x223/0xaa0 kernel/irq/handle.c:156
handle_irq_event_percpu kernel/irq/handle.c:196 [inline]
handle_irq_event+0x102/0x290 kernel/irq/handle.c:213
handle_edge_irq+0x25f/0xd00 kernel/irq/chip.c:819
asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706
__run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
handle_irq arch/x86/kernel/irq.c:230 [inline]
__common_interrupt arch/x86/kernel/irq.c:249 [inline]
common_interrupt+0x115/0x1f0 arch/x86/kernel/irq.c:239
asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:572
arch_local_irq_restore arch/x86/include/asm/paravirt.h:653 [inline]
lock_acquire+0x27b/0xaf0 kernel/locking/lockdep.c:5401
rcu_lock_acquire include/linux/rcupdate.h:248 [inline]
rcu_read_lock include/linux/rcupdate.h:641 [inline]
path_init+0x851/0x13c0 fs/namei.c:2213
path_openat+0x185/0x2730 fs/namei.c:3364
do_filp_open+0x17e/0x3c0 fs/namei.c:3396
do_open_execat+0x116/0x690 fs/exec.c:910
bprm_execve+0x508/0x1b10 fs/exec.c:1909
kernel_execve+0x370/0x460 fs/exec.c:2080
call_usermodehelper_exec_async+0x27a/0x500 kernel/umh.c:101
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
INITIAL USE at:
lock_acquire+0x1f3/0xaf0 kernel/locking/lockdep.c:5398
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x94/0xd0 kernel/locking/spinlock.c:159
input_inject_event+0xa6/0x310 drivers/input/input.c:466
__led_set_brightness drivers/leds/led-core.c:48 [inline]
led_set_brightness_nopm drivers/leds/led-core.c:275 [inline]
led_set_brightness_nosleep+0xe6/0x1a0 drivers/leds/led-core.c:292
led_set_brightness+0x134/0x170 drivers/leds/led-core.c:267
led_trigger_event drivers/leds/led-triggers.c:387 [inline]
led_trigger_event+0x70/0xd0 drivers/leds/led-triggers.c:377
kbd_led_trigger_activate+0xfa/0x130 drivers/tty/vt/keyboard.c:1005
led_trigger_set+0x61e/0xbd0 drivers/leds/led-triggers.c:195
led_trigger_set_default drivers/leds/led-triggers.c:259 [inline]
led_trigger_set_default+0x1a6/0x230 drivers/leds/led-triggers.c:246
led_classdev_register_ext+0x511/0x6a0 drivers/leds/led-class.c:412
led_classdev_register include/linux/leds.h:190 [inline]
input_leds_connect+0x3e8/0x6c0 drivers/input/input-leds.c:139
input_attach_handler+0x180/0x1f0 drivers/input/input.c:1031
input_register_device.cold+0xf0/0x243 drivers/input/input.c:2229
atkbd_connect+0x736/0x9d0 drivers/input/keyboard/atkbd.c:1293
serio_connect_driver drivers/input/serio/serio.c:47 [inline]
serio_driver_probe+0x72/0xa0 drivers/input/serio/serio.c:778
really_probe+0x282/0x9f0 drivers/base/dd.c:553
driver_probe_device+0xfe/0x1d0 drivers/base/dd.c:738
device_driver_attach+0x228/0x290 drivers/base/dd.c:1013
__driver_attach drivers/base/dd.c:1090 [inline]
__driver_attach+0xda/0x240 drivers/base/dd.c:1044
bus_for_each_dev+0x147/0x1d0 drivers/base/bus.c:305
serio_attach_driver drivers/input/serio/serio.c:808 [inline]
serio_handle_event+0x5f6/0xa30 drivers/input/serio/serio.c:227
process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
kthread+0x3af/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
}
... key at: [<ffffffff8d5c1a20>] __key.5+0x0/0x40
... acquired at:
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
spin_lock include/linux/spinlock.h:354 [inline]
evdev_pass_values+0x195/0xa30 drivers/input/evdev.c:262
evdev_events+0x20c/0x330 drivers/input/evdev.c:307
input_to_handler+0x2a0/0x4c0 drivers/input/input.c:115
input_pass_values.part.0+0x284/0x700 drivers/input/input.c:145
input_pass_values drivers/input/input.c:134 [inline]
input_handle_event+0x324/0x1390 drivers/input/input.c:399
input_inject_event+0x2f5/0x310 drivers/input/input.c:471
evdev_write+0x424/0x750 drivers/input/evdev.c:530
vfs_write+0x28e/0x700 fs/read_write.c:593
ksys_write+0x1ee/0x250 fs/read_write.c:648
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

-> (&client->buffer_lock){....}-{2:2} {
INITIAL USE at:
lock_acquire+0x1f3/0xaf0 kernel/locking/lockdep.c:5398
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
spin_lock include/linux/spinlock.h:354 [inline]
evdev_pass_values+0x195/0xa30 drivers/input/evdev.c:262
evdev_events+0x20c/0x330 drivers/input/evdev.c:307
input_to_handler+0x2a0/0x4c0 drivers/input/input.c:115
input_pass_values.part.0+0x284/0x700 drivers/input/input.c:145
input_pass_values drivers/input/input.c:134 [inline]
input_handle_event+0x324/0x1390 drivers/input/input.c:399
input_inject_event+0x2f5/0x310 drivers/input/input.c:471
evdev_write+0x424/0x750 drivers/input/evdev.c:530
vfs_write+0x28e/0x700 fs/read_write.c:593
ksys_write+0x1ee/0x250 fs/read_write.c:648
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
}
... key at: [<ffffffff8d5c1f20>] __key.4+0x0/0x40
... acquired at:
__raw_read_lock include/linux/rwlock_api_smp.h:149 [inline]
_raw_read_lock+0x5b/0x70 kernel/locking/spinlock.c:223
kill_fasync_rcu fs/fcntl.c:1002 [inline]
kill_fasync fs/fcntl.c:1023 [inline]
kill_fasync+0x14b/0x460 fs/fcntl.c:1016
__pass_event drivers/input/evdev.c:240 [inline]
evdev_pass_values+0x715/0xa30 drivers/input/evdev.c:279
evdev_events+0x20c/0x330 drivers/input/evdev.c:307
input_to_handler+0x2a0/0x4c0 drivers/input/input.c:115
input_pass_values.part.0+0x284/0x700 drivers/input/input.c:145
input_pass_values drivers/input/input.c:134 [inline]
input_handle_event+0x324/0x1390 drivers/input/input.c:399
input_inject_event+0x2f5/0x310 drivers/input/input.c:471
evdev_write+0x424/0x750 drivers/input/evdev.c:530
vfs_write+0x28e/0x700 fs/read_write.c:593
ksys_write+0x1ee/0x250 fs/read_write.c:648
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

-> (&new->fa_lock){....}-{2:2} {
(null) at:
general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
CPU: 1 PID: 6886 Comm: syz-executor198 Not tainted 5.9.0-rc4-next-20200908-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:print_lock_trace kernel/locking/lockdep.c:1751 [inline]
RIP: 0010:print_lock_class_header kernel/locking/lockdep.c:2240 [inline]
RIP: 0010:print_shortest_lock_dependencies.cold+0x110/0x2af kernel/locking/lockdep.c:2263
Code: 48 8b 04 24 48 c1 e8 03 42 80 3c 20 00 74 09 48 8b 3c 24 e8 dd fb de f9 48 8b 04 24 48 8b 00 48 8d 78 14 48 89 fa 48 c1 ea 03 <42> 0f b6 0c 22 48 89 fa 83 e2 07 83 c2 03 38 ca 7c 08 84 c9 0f 85
RSP: 0018:ffffc900055e75c0 EFLAGS: 00010003
RAX: 0000000000000001 RBX: ffffc900055e7718 RCX: 0000000000000000
RDX: 0000000000000002 RSI: ffffffff815bc817 RDI: 0000000000000015
RBP: ffffc900055e7718 R08: 0000000000000004 R09: ffff8880ae720f8b
R10: 0000000000000000 R11: 6c6c756e28202020 R12: dffffc0000000000
R13: ffffffff8c6ff160 R14: 0000000000000009 R15: 0000000000000000
FS: 0000000000fee880(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020e68000 CR3: 0000000092552000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
print_bad_irq_dependency kernel/locking/lockdep.c:2395 [inline]
check_irq_usage.cold+0x42d/0x5b0 kernel/locking/lockdep.c:2634
check_prev_add kernel/locking/lockdep.c:2823 [inline]
check_prevs_add kernel/locking/lockdep.c:2944 [inline]
validate_chain kernel/locking/lockdep.c:3562 [inline]
__lock_acquire+0x2800/0x55d0 kernel/locking/lockdep.c:4796
lock_acquire+0x1f3/0xaf0 kernel/locking/lockdep.c:5398
__raw_read_lock include/linux/rwlock_api_smp.h:149 [inline]
_raw_read_lock+0x5b/0x70 kernel/locking/spinlock.c:223
send_sigio+0x24/0x320 fs/fcntl.c:786
kill_fasync_rcu fs/fcntl.c:1009 [inline]
kill_fasync fs/fcntl.c:1023 [inline]
kill_fasync+0x205/0x460 fs/fcntl.c:1016
__pass_event drivers/input/evdev.c:240 [inline]
evdev_pass_values+0x715/0xa30 drivers/input/evdev.c:279
evdev_events+0x20c/0x330 drivers/input/evdev.c:307
input_to_handler+0x2a0/0x4c0 drivers/input/input.c:115
input_pass_values.part.0+0x284/0x700 drivers/input/input.c:145
input_pass_values drivers/input/input.c:134 [inline]
input_handle_event+0x324/0x1390 drivers/input/input.c:399
input_inject_event+0x2f5/0x310 drivers/input/input.c:471
evdev_write+0x424/0x750 drivers/input/evdev.c:530
vfs_write+0x28e/0x700 fs/read_write.c:593
ksys_write+0x1ee/0x250 fs/read_write.c:648
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x447769
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 0f 83 0b d2 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffe05f41328 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000447769
RDX: 0000000000000373 RSI: 0000000020000040 RDI: 0000000000000004
RBP: 00007ffe05f41340 R08: 00000000bb1414ac R09: 00000000bb1414ac
R10: 00000000bb1414ac R11: 0000000000000246 R12: 00007ffe05f41370
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace 0cc9cc1229a01108 ]---
RIP: 0010:print_lock_trace kernel/locking/lockdep.c:1751 [inline]
RIP: 0010:print_lock_class_header kernel/locking/lockdep.c:2240 [inline]
RIP: 0010:print_shortest_lock_dependencies.cold+0x110/0x2af kernel/locking/lockdep.c:2263
Code: 48 8b 04 24 48 c1 e8 03 42 80 3c 20 00 74 09 48 8b 3c 24 e8 dd fb de f9 48 8b 04 24 48 8b 00 48 8d 78 14 48 89 fa 48 c1 ea 03 <42> 0f b6 0c 22 48 89 fa 83 e2 07 83 c2 03 38 ca 7c 08 84 c9 0f 85
RSP: 0018:ffffc900055e75c0 EFLAGS: 00010003
RAX: 0000000000000001 RBX: ffffc900055e7718 RCX: 0000000000000000
RDX: 0000000000000002 RSI: ffffffff815bc817 RDI: 0000000000000015
RBP: ffffc900055e7718 R08: 0000000000000004 R09: ffff8880ae720f8b
R10: 0000000000000000 R11: 6c6c756e28202020 R12: dffffc0000000000
R13: ffffffff8c6ff160 R14: 0000000000000009 R15: 0000000000000000
FS: 0000000000fee880(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020e68000 CR3: 0000000092552000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
This report is generated by a bot. It may contain errors.
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[syzbot]

syzbot has bisected this issue to:

commit f08e3888574d490b31481eef6d84c61bedba7a47
Author: Boqun Feng <boqun...@gmail.com>
Date: Fri Aug 7 07:42:30 2020 +0000

lockdep: Fix recursive read lock related safe->unsafe detection

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13034be1900000
start commit: dff9f829 Add linux-next specific files for 20200908
git tree: linux-next
final oops: https://syzkaller.appspot.com/x/report.txt?x=10834be1900000
console output: https://syzkaller.appspot.com/x/log.txt?x=17034be1900000

kernel config: https://syzkaller.appspot.com/x/.config?x=37b3426c77bda44c
dashboard link: https://syzkaller.appspot.com/bug?extid=22e87cdf94021b984aa6

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=108b740d900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12daa9ed900000

Reported-by: syzbot+22e87c...@syzkaller.appspotmail.com
Fixes: f08e3888574d ("lockdep: Fix recursive read lock related safe->unsafe detection")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[Boqun Feng]

Thanks!

This is another deadlock possibility detected by lockdep's new detection
algorithm.

The deadlock happens as follow:

CPU 0 CPU 1 CPU 2
read_lock(&fown->lock);
spin_lock_irqsave(&dev->event_lock, ...)
write_lock_irq(&filp->f_owner.lock); // wait for the lock
read_lock(&fown-lock); // have to wait until the writer release
// due to the fairness
<interrupted>
spin_lock_irqsave(&dev->event_lock); // wait for the lock

The lock dependency on CPU 1 happens if there exists a call sequence:

input_inject_event():
spin_lock_irqsave(&dev->event_lock,...);
input_handle_event():
input_pass_values():
input_to_handler():
handler->event(): // evdev_event()
evdev_pass_values():
spin_lock(&client->buffer_lock);
__pass_event():
kill_fasync():
kill_fasync_rcu():
read_lock(&fa->fa_lock);
send_sigio():
read_lock(&fown->lock);

A possible fix would be replacing the read_lock() with read_lock_irq()
or read_lock_irqsave().

Regards,
Boqun