[PATCH v2] thermal: cpufreq_cooling: fix slab OOB issue

[Michael Kao]

Dear Daniel,

Kindly ping.
Can this patch be merged? Or any comment?

BR,
Michael

On Tue, 2020-12-29 at 13:08 +0800, Michael Kao wrote:
> From: brian-sy yang <brian-sy.yang at mediatek.com>
> 
> Slab OOB issue is scanned by KASAN in cpu_power_to_freq().
> If power is limited below the power of OPP0 in EM table,
> it will cause slab out-of-bound issue with negative array
> index.
> 
> Return the lowest frequency if limited power cannot found
> a suitable OPP in EM table to fix this issue.
> 
> Backtrace:
> [<ffffffd02d2a37f0>] die+0x104/0x5ac
> [<ffffffd02d2a5630>] bug_handler+0x64/0xd0
> [<ffffffd02d288ce4>] brk_handler+0x160/0x258
> [<ffffffd02d281e5c>] do_debug_exception+0x248/0x3f0
> [<ffffffd02d284488>] el1_dbg+0x14/0xbc
> [<ffffffd02d75d1d4>] __kasan_report+0x1dc/0x1e0
> [<ffffffd02d75c2e0>] kasan_report+0x10/0x20
> [<ffffffd02d75def8>] __asan_report_load8_noabort+0x18/0x28
> [<ffffffd02e6fce5c>] cpufreq_power2state+0x180/0x43c
> [<ffffffd02e6ead80>] power_actor_set_power+0x114/0x1d4
> [<ffffffd02e6fac24>] allocate_power+0xaec/0xde0
> [<ffffffd02e6f9f80>] power_allocator_throttle+0x3ec/0x5a4
> [<ffffffd02e6ea888>] handle_thermal_trip+0x160/0x294
> [<ffffffd02e6edd08>] thermal_zone_device_check+0xe4/0x154
> [<ffffffd02d351cb4>] process_one_work+0x5e4/0xe28
> [<ffffffd02d352f44>] worker_thread+0xa4c/0xfac
> [<ffffffd02d360124>] kthread+0x33c/0x358
> [<ffffffd02d289940>] ret_from_fork+0xc/0x18
> 
> Fixes: 371a3bc79c11b ("thermal/drivers/cpufreq_cooling: Fix wrong frequency converted from power")
> Signed-off-by: brian-sy yang <brian-sy.yang at mediatek.com>
> Signed-off-by: Michael Kao <michael.kao at mediatek.com>
> Reviewed-by: Lukasz Luba <lukasz.luba at arm.com>
> ---
> 
> Changes from v1:
> - add fixes tag
> - add reviewed-by
> 
>  drivers/thermal/cpufreq_cooling.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/thermal/cpufreq_cooling.c b/drivers/thermal/cpufreq_cooling.c
> index cc2959f22f01..fb33b3480a8f 100644
> --- a/drivers/thermal/cpufreq_cooling.c
> +++ b/drivers/thermal/cpufreq_cooling.c
> @@ -123,7 +123,7 @@ static u32 cpu_power_to_freq(struct cpufreq_cooling_device *cpufreq_cdev,
>  {
>  	int i;
>  
> -	for (i = cpufreq_cdev->max_level; i >= 0; i--) {
> +	for (i = cpufreq_cdev->max_level; i > 0; i--) {
>  		if (power >= cpufreq_cdev->em->table[i].power)
>  			break;
>  	}