cpufreq: governor: Use kobject release() method to free dbs_data

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

cpufreq: governor: Use kobject release() method to free dbs_data

The struct dbs_data embeds a struct gov_attr_set and

the struct gov_attr_set embeds a kobject. Since every kobject must have

a release() method and we can't use kfree() to free it directly,

so introduce cpufreq_dbs_data_release() to release the dbs_data via

the kobject::release() method. This fixes the calltrace like below:

ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x34

WARNING: CPU: 12 PID: 810 at lib/debugobjects.c:505 debug_print_object+0xb8/0x100

Modules linked in:

CPU: 12 PID: 810 Comm: sh Not tainted 5.16.0-next-20220120-yocto-standard+ #536

Hardware name: Marvell OcteonTX CN96XX board (DT)

pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)

pc : debug_print_object+0xb8/0x100

lr : debug_print_object+0xb8/0x100

sp : ffff80001dfcf9a0

x29: ffff80001dfcf9a0 x28: 0000000000000001 x27: ffff0001464f0000

x26: 0000000000000000 x25: ffff8000090e3f00 x24: ffff80000af60210

x23: ffff8000094dfb78 x22: ffff8000090e3f00 x21: ffff0001080b7118

x20: ffff80000aeb2430 x19: ffff800009e8f5e0 x18: 0000000000000000

x17: 0000000000000002 x16: 00004d62e58be040 x15: 013590470523aff8

x14: ffff8000090e1828 x13: 0000000001359047 x12: 00000000f5257d14

x11: 0000000000040591 x10: 0000000066c1ffea x9 : ffff8000080d15e0

x8 : ffff80000a1765a8 x7 : 0000000000000000 x6 : 0000000000000001

x5 : ffff800009e8c000 x4 : ffff800009e8c760 x3 : 0000000000000000

x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0001474ed040

Call trace:

debug_print_object+0xb8/0x100

__debug_check_no_obj_freed+0x1d0/0x25c

debug_check_no_obj_freed+0x24/0xa0

kfree+0x11c/0x440

cpufreq_dbs_governor_exit+0xa8/0xac

cpufreq_exit_governor+0x44/0x90

cpufreq_set_policy+0x29c/0x570

store_scaling_governor+0x110/0x154

store+0xb0/0xe0

sysfs_kf_write+0x58/0x84

kernfs_fop_write_iter+0x12c/0x1c0

new_sync_write+0xf0/0x18c

vfs_write+0x1cc/0x220

ksys_write+0x74/0x100

__arm64_sys_write+0x28/0x3c

invoke_syscall.constprop.0+0x58/0xf0

do_el0_svc+0x70/0x170

el0_svc+0x54/0x190

el0t_64_sync_handler+0xa4/0x130

el0t_64_sync+0x1a0/0x1a4

irq event stamp: 189006

hardirqs last enabled at (189005): [<ffff8000080849d0>] finish_task_switch.isra.0+0xe0/0x2c0

hardirqs last disabled at (189006): [<ffff8000090667a4>] el1_dbg+0x24/0xa0

softirqs last enabled at (188966): [<ffff8000080106d0>] __do_softirq+0x4b0/0x6a0

softirqs last disabled at (188957): [<ffff80000804a618>] __irq_exit_rcu+0x108/0x1a4

[ rjw: Because can be freed by the gov_attr_set_put() in

cpufreq_dbs_governor_exit() now, it is also necessary to put the

invocation of the governor ->exit() callback into the new

cpufreq_dbs_data_release() function. ]