possible deadlock in perf_event_for_each_child

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syzbot

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Apr 14, 2019, 5:58:05 AM4/14/19
to syzkaller...@googlegroups.com
Hello,

syzbot found the following crash on:

HEAD commit: 1ec8f1f0 Linux 4.14.111
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1185b65b200000
kernel config: https://syzkaller.appspot.com/x/.config?x=fdadf290ea9fc6f9
dashboard link: https://syzkaller.appspot.com/bug?extid=c82316340fea6502aaeb
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+c82316...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
4.14.111 #1 Not tainted
------------------------------------------------------
syz-executor.5/24763 is trying to acquire lock:
(&event->child_mutex){+.+.}, at: [<ffffffff816aa32a>]
perf_event_for_each_child+0x8a/0x160 kernel/events/core.c:4682

but task is already holding lock:
(&cpuctx_mutex){+.+.}, at: [<ffffffff816bb020>]
perf_event_ctx_lock_nested+0x150/0x2c0 kernel/events/core.c:1235

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #5 (&cpuctx_mutex){+.+.}:
lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
perf_event_init_cpu+0xc2/0x170 kernel/events/core.c:11221
perf_event_init+0x2d8/0x31a kernel/events/core.c:11268
start_kernel+0x3b9/0x700 init/main.c:621
x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:380
x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:361
secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:240

-> #4 (pmus_lock){+.+.}:
lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
perf_event_init_cpu+0x2f/0x170 kernel/events/core.c:11215
cpuhp_invoke_callback+0x1ec/0x1ac0 kernel/cpu.c:184
cpuhp_up_callbacks kernel/cpu.c:572 [inline]
_cpu_up+0x228/0x530 kernel/cpu.c:1134
do_cpu_up+0x121/0x150 kernel/cpu.c:1169
cpu_up+0x1b/0x20 kernel/cpu.c:1177
smp_init+0x157/0x173 kernel/smp.c:578
kernel_init_freeable+0x30e/0x538 init/main.c:1067
kernel_init+0x12/0x162 init/main.c:999
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:402

-> #3 (cpu_hotplug_lock.rw_sem){++++}:
lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994
percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:36
[inline]
percpu_down_read include/linux/percpu-rwsem.h:59 [inline]
cpus_read_lock+0x3d/0xc0 kernel/cpu.c:295
static_key_slow_inc+0x13/0x30 kernel/jump_label.c:123
tracepoint_add_func kernel/tracepoint.c:223 [inline]
tracepoint_probe_register_prio+0x4dc/0x6d0 kernel/tracepoint.c:283
tracepoint_probe_register+0x2b/0x40 kernel/tracepoint.c:304
trace_event_reg+0x277/0x330 kernel/trace/trace_events.c:305
perf_trace_event_reg kernel/trace/trace_event_perf.c:122 [inline]
perf_trace_event_init kernel/trace/trace_event_perf.c:197 [inline]
perf_trace_init+0x450/0xaa0 kernel/trace/trace_event_perf.c:221
perf_tp_event_init+0x7d/0xf0 kernel/events/core.c:8104
perf_try_init_event+0x170/0x210 kernel/events/core.c:9340
perf_init_event kernel/events/core.c:9378 [inline]
perf_event_alloc.part.0+0xd48/0x2540 kernel/events/core.c:9638
perf_event_alloc kernel/events/core.c:9991 [inline]
SYSC_perf_event_open+0xa2d/0x24c0 kernel/events/core.c:10095
SyS_perf_event_open+0x34/0x40 kernel/events/core.c:9981
do_syscall_64+0x1eb/0x630 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7

-> #2 (tracepoints_mutex){+.+.}:
lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
tracepoint_probe_register_prio+0x36/0x6d0 kernel/tracepoint.c:279
tracepoint_probe_register+0x2b/0x40 kernel/tracepoint.c:304
trace_event_reg+0x277/0x330 kernel/trace/trace_events.c:305
perf_trace_event_reg kernel/trace/trace_event_perf.c:122 [inline]
perf_trace_event_init kernel/trace/trace_event_perf.c:197 [inline]
perf_trace_init+0x450/0xaa0 kernel/trace/trace_event_perf.c:221
perf_tp_event_init+0x7d/0xf0 kernel/events/core.c:8104
perf_try_init_event+0x170/0x210 kernel/events/core.c:9340
perf_init_event kernel/events/core.c:9378 [inline]
perf_event_alloc.part.0+0xd48/0x2540 kernel/events/core.c:9638
perf_event_alloc kernel/events/core.c:9991 [inline]
SYSC_perf_event_open+0xa2d/0x24c0 kernel/events/core.c:10095
SyS_perf_event_open+0x34/0x40 kernel/events/core.c:9981
do_syscall_64+0x1eb/0x630 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7

-> #1 (event_mutex){+.+.}:
lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
perf_trace_destroy+0x28/0x100 kernel/trace/trace_event_perf.c:234
tp_perf_event_destroy+0x16/0x20 kernel/events/core.c:8088
_free_event+0x332/0xe70 kernel/events/core.c:4238
free_event+0x38/0x50 kernel/events/core.c:4265
perf_event_release_kernel+0x364/0x7a0 kernel/events/core.c:4409
perf_release+0x37/0x50 kernel/events/core.c:4435
__fput+0x277/0x7a0 fs/file_table.c:210
____fput+0x16/0x20 fs/file_table.c:244
task_work_run+0x119/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1da/0x220 arch/x86/entry/common.c:163
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:267 [inline]
do_syscall_64+0x4a9/0x630 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x42/0xb7

-> #0 (&event->child_mutex){+.+.}:
check_prev_add kernel/locking/lockdep.c:1901 [inline]
check_prevs_add kernel/locking/lockdep.c:2018 [inline]
validate_chain kernel/locking/lockdep.c:2460 [inline]
__lock_acquire+0x2c89/0x45e0 kernel/locking/lockdep.c:3487
lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
perf_event_for_each_child+0x8a/0x160 kernel/events/core.c:4682
_perf_ioctl kernel/events/core.c:4866 [inline]
perf_ioctl+0x1df/0xcb0 kernel/events/core.c:4878
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x7b9/0x1070 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
do_syscall_64+0x1eb/0x630 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7

other info that might help us debug this:

Chain exists of:
&event->child_mutex --> pmus_lock --> &cpuctx_mutex

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&cpuctx_mutex);
lock(pmus_lock);
lock(&cpuctx_mutex);
lock(&event->child_mutex);

*** DEADLOCK ***

1 lock held by syz-executor.5/24763:
#0: (&cpuctx_mutex){+.+.}, at: [<ffffffff816bb020>]
perf_event_ctx_lock_nested+0x150/0x2c0 kernel/events/core.c:1235

stack backtrace:
CPU: 0 PID: 24763 Comm: syz-executor.5 Not tainted 4.14.111 #1
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x138/0x19c lib/dump_stack.c:53
print_circular_bug.isra.0.cold+0x1cc/0x28f kernel/locking/lockdep.c:1258
check_prev_add kernel/locking/lockdep.c:1901 [inline]
check_prevs_add kernel/locking/lockdep.c:2018 [inline]
validate_chain kernel/locking/lockdep.c:2460 [inline]
__lock_acquire+0x2c89/0x45e0 kernel/locking/lockdep.c:3487
lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
perf_event_for_each_child+0x8a/0x160 kernel/events/core.c:4682
_perf_ioctl kernel/events/core.c:4866 [inline]
perf_ioctl+0x1df/0xcb0 kernel/events/core.c:4878
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x7b9/0x1070 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
do_syscall_64+0x1eb/0x630 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x458c29
RSP: 002b:00007f7efe66ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458c29
RDX: 0000000000000000 RSI: 0000000000002403 RDI: 0000000000000004
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f7efe66b6d4
R13: 00000000004c2179 R14: 00000000004d4ac0 R15: 00000000ffffffff
kobject: 'loop4' (ffff8880a4ac0120): kobject_uevent_env
kobject: 'loop4' (ffff8880a4ac0120): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop2' (ffff8880a4a106a0): kobject_uevent_env
kobject: 'loop2' (ffff8880a4a106a0): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'loop0' (ffff8880a4952560): kobject_uevent_env
kobject: 'loop0' (ffff8880a4952560): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop3' (ffff8880a4a560a0): kobject_uevent_env
kobject: 'loop3' (ffff8880a4a560a0): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop5' (ffff8880a4b0ca20): kobject_uevent_env
kobject: 'loop5' (ffff8880a4b0ca20): fill_kobj_path: path
= '/devices/virtual/block/loop5'
kobject: 'loop5' (ffff8880a4b0ca20): kobject_uevent_env
kobject: 'loop5' (ffff8880a4b0ca20): fill_kobj_path: path
= '/devices/virtual/block/loop5'
kobject: 'loop0' (ffff8880a4952560): kobject_uevent_env
kobject: 'loop0' (ffff8880a4952560): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop5' (ffff8880a4b0ca20): kobject_uevent_env
kobject: 'loop5' (ffff8880a4b0ca20): fill_kobj_path: path
= '/devices/virtual/block/loop5'
kobject: 'loop1' (ffff8880a49c9760): kobject_uevent_env
kobject: 'loop1' (ffff8880a49c9760): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop5' (ffff8880a4b0ca20): kobject_uevent_env
kobject: 'loop5' (ffff8880a4b0ca20): fill_kobj_path: path
= '/devices/virtual/block/loop5'
kobject: 'loop3' (ffff8880a4a560a0): kobject_uevent_env
kobject: 'loop3' (ffff8880a4a560a0): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop2' (ffff8880a4a106a0): kobject_uevent_env
kobject: 'loop2' (ffff8880a4a106a0): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'loop4' (ffff8880a4ac0120): kobject_uevent_env
kobject: 'loop4' (ffff8880a4ac0120): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop5' (ffff8880a4b0ca20): kobject_uevent_env
kobject: 'loop5' (ffff8880a4b0ca20): fill_kobj_path: path
= '/devices/virtual/block/loop5'
kobject: 'loop2' (ffff8880a4a106a0): kobject_uevent_env
kobject: 'loop2' (ffff8880a4a106a0): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'loop5' (ffff8880a4b0ca20): kobject_uevent_env
kobject: 'loop5' (ffff8880a4b0ca20): fill_kobj_path: path
= '/devices/virtual/block/loop5'
netlink: 8 bytes leftover after parsing attributes in process
`syz-executor.3'.
kobject: 'loop0' (ffff8880a4952560): kobject_uevent_env
kobject: 'loop0' (ffff8880a4952560): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'rx-0' (ffff88808ee906d0): kobject_cleanup, parent ffff88808eb3ae48
kobject: 'loop2' (ffff8880a4a106a0): kobject_uevent_env
kobject: 'rx-0' (ffff88808ee906d0): auto cleanup 'remove' event
kobject: 'loop2' (ffff8880a4a106a0): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'rx-0' (ffff88808ee906d0): kobject_uevent_env
kobject: 'loop5' (ffff8880a4b0ca20): kobject_uevent_env
kobject: 'loop5' (ffff8880a4b0ca20): fill_kobj_path: path
= '/devices/virtual/block/loop5'
kobject: 'loop2' (ffff8880a4a106a0): kobject_uevent_env
kobject: 'rx-0' (ffff88808ee906d0): fill_kobj_path: path
= '/devices/virtual/net/nlmon0/queues/rx-0'
kobject: 'loop2' (ffff8880a4a106a0): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'rx-0' (ffff88808ee906d0): auto cleanup kobject_del
kobject: 'loop4' (ffff8880a4ac0120): kobject_uevent_env
kobject: 'rx-0' (ffff88808ee906d0): calling ktype release
kobject: 'loop4' (ffff8880a4ac0120): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'rx-0': free name
kobject: 'tx-0' (ffff8880909bd318): kobject_cleanup, parent ffff88808eb3ae48
kobject: 'loop1' (ffff8880a49c9760): kobject_uevent_env
kobject: 'loop1' (ffff8880a49c9760): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'tx-0' (ffff8880909bd318): auto cleanup 'remove' event
kobject: 'loop0' (ffff8880a4952560): kobject_uevent_env
kobject: 'tx-0' (ffff8880909bd318): kobject_uevent_env
kobject: 'loop0' (ffff8880a4952560): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'tx-0' (ffff8880909bd318): fill_kobj_path: path
= '/devices/virtual/net/nlmon0/queues/tx-0'
kobject: 'loop5' (ffff8880a4b0ca20): kobject_uevent_env
kobject: 'tx-0' (ffff8880909bd318): auto cleanup kobject_del
kobject: 'tx-0' (ffff8880909bd318): calling ktype release
kobject: 'loop5' (ffff8880a4b0ca20): fill_kobj_path: path
= '/devices/virtual/block/loop5'
kobject: 'tx-0': free name
kobject: 'queues' (ffff88808eb3ae48): kobject_cleanup, parent
(null)
kobject: 'queues' (ffff88808eb3ae48): calling ktype release
kobject: 'queues' (ffff88808eb3ae48): kset_release
kobject: 'loop2' (ffff8880a4a106a0): kobject_uevent_env
kobject: 'queues': free name
kobject: 'nlmon0' (ffff88806d128830): kobject_uevent_env
kobject: 'nlmon0' (ffff88806d128830): fill_kobj_path: path
= '/devices/virtual/net/nlmon0'
kobject: 'loop2' (ffff8880a4a106a0): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'loop1' (ffff8880a49c9760): kobject_uevent_env
kobject: 'loop1' (ffff8880a49c9760): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop1' (ffff8880a49c9760): kobject_uevent_env
kobject: 'loop1' (ffff8880a49c9760): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'nlmon0' (ffff88806d128830): kobject_cleanup, parent
(null)
kobject: 'loop4' (ffff8880a4ac0120): kobject_uevent_env
kobject: 'nlmon0' (ffff88806d128830): calling ktype release
kobject: 'loop4' (ffff8880a4ac0120): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'nlmon0': free name
kobject: 'loop1' (ffff8880a49c9760): kobject_uevent_env
kobject: 'loop1' (ffff8880a49c9760): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop1' (ffff8880a49c9760): kobject_uevent_env
kobject: 'loop1' (ffff8880a49c9760): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop0' (ffff8880a4952560): kobject_uevent_env
kobject: 'loop0' (ffff8880a4952560): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop4' (ffff8880a4ac0120): kobject_uevent_env
kobject: 'loop4' (ffff8880a4ac0120): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop3' (ffff8880a4a560a0): kobject_uevent_env
netlink: 8 bytes leftover after parsing attributes in process
`syz-executor.3'.
kobject: 'loop3' (ffff8880a4a560a0): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop5' (ffff8880a4b0ca20): kobject_uevent_env
kobject: 'loop5' (ffff8880a4b0ca20): fill_kobj_path: path
= '/devices/virtual/block/loop5'
kobject: 'loop0' (ffff8880a4952560): kobject_uevent_env
kobject: 'loop0' (ffff8880a4952560): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop2' (ffff8880a4a106a0): kobject_uevent_env
kobject: 'loop2' (ffff8880a4a106a0): fill_kobj_path: path
= '/devices/virtual/block/loop2'
netlink: 8 bytes leftover after parsing attributes in process
`syz-executor.3'.
kobject: 'loop3' (ffff8880a4a560a0): kobject_uevent_env
kobject: 'loop3' (ffff8880a4a560a0): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop5' (ffff8880a4b0ca20): kobject_uevent_env
kobject: 'loop5' (ffff8880a4b0ca20): fill_kobj_path: path
= '/devices/virtual/block/loop5'
netlink: 8 bytes leftover after parsing attributes in process
`syz-executor.3'.
kobject: 'loop0' (ffff8880a4952560): kobject_uevent_env
kobject: 'loop0' (ffff8880a4952560): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop4' (ffff8880a4ac0120): kobject_uevent_env
kobject: 'loop4' (ffff8880a4ac0120): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop1' (ffff8880a49c9760): kobject_uevent_env
kobject: 'loop1' (ffff8880a49c9760): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop3' (ffff8880a4a560a0): kobject_uevent_env
kobject: 'loop3' (ffff8880a4a560a0): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop1' (ffff8880a49c9760): kobject_uevent_env
kobject: 'loop1' (ffff8880a49c9760): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop3' (ffff8880a4a560a0): kobject_uevent_env
kobject: 'loop3' (ffff8880a4a560a0): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop1' (ffff8880a49c9760): kobject_uevent_env
kobject: 'loop1' (ffff8880a49c9760): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop4' (ffff8880a4ac0120): kobject_uevent_env
kobject: 'loop4' (ffff8880a4ac0120): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop2' (ffff8880a4a106a0): kobject_uevent_env
kobject: 'loop2' (ffff8880a4a106a0): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'loop1' (ffff8880a49c9760): kobject_uevent_env
kobject: 'loop1' (ffff8880a49c9760): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop3' (ffff8880a4a560a0): kobject_uevent_env
kobject: 'loop3' (ffff8880a4a560a0): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop4' (ffff8880a4ac0120): kobject_uevent_env
kobject: 'loop4' (ffff8880a4ac0120): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop1' (ffff8880a49c9760): kobject_uevent_env
kobject: 'loop1' (ffff8880a49c9760): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop5' (ffff8880a4b0ca20): kobject_uevent_env
kobject: 'loop5' (ffff8880a4b0ca20): fill_kobj_path: path
= '/devices/virtual/block/loop5'
kobject: 'loop0' (ffff8880a4952560): kobject_uevent_env
kobject: 'loop0' (ffff8880a4952560): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop4' (ffff8880a4ac0120): kobject_uevent_env
kobject: 'loop4' (ffff8880a4ac0120): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop1' (ffff8880a49c9760): kobject_uevent_env
kobject: 'loop1' (ffff8880a49c9760): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop3' (ffff8880a4a560a0): kobject_uevent_env
kobject: 'loop3' (ffff8880a4a560a0): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop1' (ffff8880a49c9760): kobject_uevent_env
kobject: 'loop1' (ffff8880a49c9760): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop3' (ffff8880a4a560a0): kobject_uevent_env
kobject: 'loop3' (ffff8880a4a560a0): fill_kobj_path: path
= '/devices/virtual/block/loop3'


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
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syzbot

unread,
Jan 18, 2021, 7:21:25 PM1/18/21
to syzkaller...@googlegroups.com
syzbot has found a reproducer for the following issue on:

HEAD commit: 2762b48e Linux 4.14.216
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11e0a384d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=e8574522d7c28056
dashboard link: https://syzkaller.appspot.com/bug?extid=c82316340fea6502aaeb
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10970bd0d00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11680520d00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c82316...@syzkaller.appspotmail.com

IPVS: ftp: loaded support on port[0] = 21
======================================================
WARNING: possible circular locking dependency detected
4.14.216-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor858/8018 is trying to acquire lock:
(&event->child_mutex){+.+.}, at: [<ffffffff8162e492>] perf_event_for_each_child+0x82/0x140 kernel/events/core.c:4688

but task is already holding lock:
(&cpuctx_mutex){+.+.}, at: [<ffffffff81632efd>] perf_event_ctx_lock_nested+0x14d/0x2c0 kernel/events/core.c:1241

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #5 (&cpuctx_mutex){+.+.}:
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0xc4/0x1310 kernel/locking/mutex.c:893
perf_event_init_cpu+0xb7/0x170 kernel/events/core.c:11250
perf_event_init+0x2cc/0x308 kernel/events/core.c:11297
start_kernel+0x46a/0x770 init/main.c:620
secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:240

-> #4 (pmus_lock){+.+.}:
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0xc4/0x1310 kernel/locking/mutex.c:893
perf_event_init_cpu+0x2c/0x170 kernel/events/core.c:11244
cpuhp_invoke_callback+0x1e6/0x1a80 kernel/cpu.c:184
cpuhp_up_callbacks kernel/cpu.c:572 [inline]
_cpu_up+0x219/0x500 kernel/cpu.c:1144
do_cpu_up+0x9a/0x160 kernel/cpu.c:1179
smp_init+0x197/0x1ac kernel/smp.c:578
kernel_init_freeable+0x3f4/0x614 init/main.c:1068
kernel_init+0xd/0x166 init/main.c:1000
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

-> #3 (cpu_hotplug_lock.rw_sem){++++}:
percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:36 [inline]
percpu_down_read include/linux/percpu-rwsem.h:59 [inline]
cpus_read_lock+0x39/0xc0 kernel/cpu.c:295
static_key_slow_inc+0xe/0x20 kernel/jump_label.c:123
tracepoint_add_func+0x517/0x750 kernel/tracepoint.c:223
tracepoint_probe_register_prio kernel/tracepoint.c:283 [inline]
tracepoint_probe_register+0x8c/0xc0 kernel/tracepoint.c:304
trace_event_reg+0x272/0x330 kernel/trace/trace_events.c:305
perf_trace_event_reg kernel/trace/trace_event_perf.c:122 [inline]
perf_trace_event_init kernel/trace/trace_event_perf.c:197 [inline]
perf_trace_init+0x424/0xa30 kernel/trace/trace_event_perf.c:221
perf_tp_event_init+0x79/0xf0 kernel/events/core.c:8138
perf_try_init_event+0x15b/0x1f0 kernel/events/core.c:9369
perf_init_event kernel/events/core.c:9407 [inline]
perf_event_alloc.part.0+0xe2d/0x2640 kernel/events/core.c:9667
perf_event_alloc kernel/events/core.c:10020 [inline]
SYSC_perf_event_open kernel/events/core.c:10124 [inline]
SyS_perf_event_open+0x67f/0x24b0 kernel/events/core.c:10010
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

-> #2 (tracepoints_mutex){+.+.}:
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0xc4/0x1310 kernel/locking/mutex.c:893
tracepoint_probe_register_prio kernel/tracepoint.c:279 [inline]
tracepoint_probe_register+0x68/0xc0 kernel/tracepoint.c:304
trace_event_reg+0x272/0x330 kernel/trace/trace_events.c:305
perf_trace_event_reg kernel/trace/trace_event_perf.c:122 [inline]
perf_trace_event_init kernel/trace/trace_event_perf.c:197 [inline]
perf_trace_init+0x424/0xa30 kernel/trace/trace_event_perf.c:221
perf_tp_event_init+0x79/0xf0 kernel/events/core.c:8138
perf_try_init_event+0x15b/0x1f0 kernel/events/core.c:9369
perf_init_event kernel/events/core.c:9407 [inline]
perf_event_alloc.part.0+0xe2d/0x2640 kernel/events/core.c:9667
perf_event_alloc kernel/events/core.c:10020 [inline]
SYSC_perf_event_open kernel/events/core.c:10124 [inline]
SyS_perf_event_open+0x67f/0x24b0 kernel/events/core.c:10010
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

-> #1 (event_mutex){+.+.}:
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0xc4/0x1310 kernel/locking/mutex.c:893
perf_trace_destroy+0x23/0xf0 kernel/trace/trace_event_perf.c:234
_free_event+0x321/0xe20 kernel/events/core.c:4244
free_event+0x32/0x40 kernel/events/core.c:4271
perf_event_release_kernel+0x368/0x8a0 kernel/events/core.c:4415
perf_release+0x33/0x40 kernel/events/core.c:4441
__fput+0x25f/0x7a0 fs/file_table.c:210
task_work_run+0x11f/0x190 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0xa44/0x2850 kernel/exit.c:868
do_group_exit+0x100/0x2e0 kernel/exit.c:965
get_signal+0x38d/0x1ca0 kernel/signal.c:2423
do_signal+0x7c/0x1550 arch/x86/kernel/signal.c:814
exit_to_usermode_loop+0x160/0x200 arch/x86/entry/common.c:160
prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x46/0xbb

-> #0 (&event->child_mutex){+.+.}:
lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0xc4/0x1310 kernel/locking/mutex.c:893
perf_event_for_each_child+0x82/0x140 kernel/events/core.c:4688
perf_event_for_each kernel/events/core.c:4705 [inline]
_perf_ioctl+0x3db/0x1a40 kernel/events/core.c:4873
perf_ioctl+0x55/0x80 kernel/events/core.c:4887
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x75a/0xff0 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

other info that might help us debug this:

Chain exists of:
&event->child_mutex --> pmus_lock --> &cpuctx_mutex

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&cpuctx_mutex);
lock(pmus_lock);
lock(&cpuctx_mutex);
lock(&event->child_mutex);

*** DEADLOCK ***

1 lock held by syz-executor858/8018:
#0: (&cpuctx_mutex){+.+.}, at: [<ffffffff81632efd>] perf_event_ctx_lock_nested+0x14d/0x2c0 kernel/events/core.c:1241

stack backtrace:
CPU: 0 PID: 8018 Comm: syz-executor858 Not tainted 4.14.216-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x1b2/0x281 lib/dump_stack.c:58
print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1258
check_prev_add kernel/locking/lockdep.c:1905 [inline]
check_prevs_add kernel/locking/lockdep.c:2022 [inline]
validate_chain kernel/locking/lockdep.c:2464 [inline]
__lock_acquire+0x2e0e/0x3f20 kernel/locking/lockdep.c:3491
lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0xc4/0x1310 kernel/locking/mutex.c:893
perf_event_for_each_child+0x82/0x140 kernel/events/core.c:4688
perf_event_for_each kernel/events/core.c:4705 [inline]
_perf_ioctl+0x3db/0x1a40 kernel/events/core.c:4873
perf_ioctl+0x55/0x80 kernel/events/core.c:4887
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x75a/0xff0 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x44a8c9
RSP: 002b:00007f24b291cdb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000006dbc28 RCX: 000000000044a8c9
RDX: 0000000000000003 RSI: 0000000000002403 RDI: 0000000000000004
RBP: 00000000006dbc20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc2c
R13: 00007ffdf2e14cbf R14: 00007f24b291d9c0 R15: 0000000000000000

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