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Subject: Re: [PATCH] thermal: Fix a NULL pointer dereference
To:     David Collins <quic_collinsd@quicinc.com>,
        Zhang Rui <rui.zhang@intel.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Amit Kucheria <amitk@kernel.org>
Cc:     linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
        stable@vger.kernel.org
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 <fe7ba5a5-d39a-dd0a-5cd3-f80ff163162a@quicinc.com>
From:   Subbaraman Narayanamurthy <quic_subbaram@quicinc.com>
Message-ID: <fa99e05e-43fd-a737-9fe2-753d9ae70530@quicinc.com>
Date:   Tue, 7 Sep 2021 11:32:42 -0700
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On 9/3/21 6:07 PM, David Collins wrote:
> On 9/3/21 5:34 PM, Subbaraman Narayanamurthy wrote:
>> of_parse_thermal_zones() parses the thermal-zones node and registers a
>> thermal_zone device for each subnode. However, if a thermal zone is
>> consuming a thermal sensor and that thermal sensor device hasn't probed
>> yet, an attempt to set trip_point_*_temp for that thermal zone device
>> can cause a NULL pointer dereference. Fix it.
>>
>>   console:/sys/class/thermal/thermal_zone87 # echo 120000 > trip_point_0_temp
>>   ...
>>   Unable to handle kernel NULL pointer dereference at virtual address 0000000000000020
>>   ...
>>   Call trace:
>>    of_thermal_set_trip_temp+0x40/0xc4
>>    trip_point_temp_store+0xc0/0x1dc
>>    dev_attr_store+0x38/0x88
>>    sysfs_kf_write+0x64/0xc0
>>    kernfs_fop_write_iter+0x108/0x1d0
>>    vfs_write+0x2f4/0x368
>>    ksys_write+0x7c/0xec
>>    __arm64_sys_write+0x20/0x30
>>    el0_svc_common.llvm.7279915941325364641+0xbc/0x1bc
>>    do_el0_svc+0x28/0xa0
>>    el0_svc+0x14/0x24
>>    el0_sync_handler+0x88/0xec
>>    el0_sync+0x1c0/0x200
>>
>> Cc: stable@vger.kernel.org
>> Suggested-by: David Collins <quic_collinsd@quicinc.com>
>> Signed-off-by: Subbaraman Narayanamurthy <quic_subbaram@quicinc.com>
>> ---
>>   drivers/thermal/thermal_of.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/thermal/thermal_of.c b/drivers/thermal/thermal_of.c
>> index 6379f26..ba53252 100644
>> --- a/drivers/thermal/thermal_of.c
>> +++ b/drivers/thermal/thermal_of.c
>> @@ -301,7 +301,7 @@ static int of_thermal_set_trip_temp(struct thermal_zone_device *tz, int trip,
>>       if (trip >= data->ntrips || trip < 0)
>>           return -EDOM;
>>   -    if (data->ops->set_trip_temp) {
>> +    if (data->ops && data->ops->set_trip_temp) {
>>           int ret;
>>             ret = data->ops->set_trip_temp(data->sensor_data, trip, temp);
>>
>
> It looks like the same kind of data->ops null pointer dereference issue is present in three other functions within this file: of_thermal_get_temp(), of_thermal_set_emul_temp(), and of_thermal_get_trend().  Should those be fixed along with of_thermal_set_trip_temp() in a single patch?

Sure, I can make those changes in this patch itself.

>
> Thanks,
> David