audit: fix possible soft lockup in __audit_inode_child()

In the Linux kernel, the following vulnerability has been resolved:

audit: fix possible soft lockup in __audit_inode_child()

Tracefs or debugfs maybe cause hundreds to thousands of PATH records,

too many PATH records maybe cause soft lockup.

For example:

1. CONFIG_KASAN=y && CONFIG_PREEMPTION=n

2. auditctl -a exit,always -S open -k key

3. sysctl -w kernel.watchdog_thresh=5

4. mkdir /sys/kernel/debug/tracing/instances/test

There may be a soft lockup as follows:

watchdog: BUG: soft lockup - CPU#45 stuck for 7s! [mkdir:15498]

Kernel panic - not syncing: softlockup: hung tasks

Call trace:

dump_backtrace+0x0/0x30c

show_stack+0x20/0x30

dump_stack+0x11c/0x174

panic+0x27c/0x494

watchdog_timer_fn+0x2bc/0x390

__run_hrtimer+0x148/0x4fc

__hrtimer_run_queues+0x154/0x210

hrtimer_interrupt+0x2c4/0x760

arch_timer_handler_phys+0x48/0x60

handle_percpu_devid_irq+0xe0/0x340

__handle_domain_irq+0xbc/0x130

gic_handle_irq+0x78/0x460

el1_irq+0xb8/0x140

__audit_inode_child+0x240/0x7bc

tracefs_create_file+0x1b8/0x2a0

trace_create_file+0x18/0x50

event_create_dir+0x204/0x30c

__trace_add_new_event+0xac/0x100

event_trace_add_tracer+0xa0/0x130

trace_array_create_dir+0x60/0x140

trace_array_create+0x1e0/0x370

instance_mkdir+0x90/0xd0

tracefs_syscall_mkdir+0x68/0xa0

vfs_mkdir+0x21c/0x34c

do_mkdirat+0x1b4/0x1d4

__arm64_sys_mkdirat+0x4c/0x60

el0_svc_common.constprop.0+0xa8/0x240

do_el0_svc+0x8c/0xc0

el0_svc+0x20/0x30

el0_sync_handler+0xb0/0xb4

el0_sync+0x160/0x180

Therefore, we add cond_resched() to __audit_inode_child() to fix it.