Re: [patch net] dpll: sanitize possible null pointer dereference in dpll_pin_parent_pin_set()

[Jiri Pirko <jiri@resnulli.us>]

Mon, Dec 11, 2023 at 11:46:24AM CET, vadim.fedorenko@linux.dev wrote:
>On 11/12/2023 08:37, Jiri Pirko wrote:
>> From: Jiri Pirko <jiri@nvidia.com>
>> 
>> User may not pass DPLL_A_PIN_STATE attribute in the pin set operation
>> message. Sanitize that by checking if the attr pointer is not null
>> and process the passed state attribute value only in that case.
>> 
>> Reported-by: Xingyuan Mo <hdthky0@gmail.com>
>> Fixes: 9d71b54b65b1 ("dpll: netlink: Add DPLL framework base functions")
>> Signed-off-by: Jiri Pirko <jiri@nvidia.com>
>> ---
>>   drivers/dpll/dpll_netlink.c | 13 ++++++++-----
>>   1 file changed, 8 insertions(+), 5 deletions(-)
>> 
>> diff --git a/drivers/dpll/dpll_netlink.c b/drivers/dpll/dpll_netlink.c
>> index 442a0ebeb953..ce7cf736f020 100644
>> --- a/drivers/dpll/dpll_netlink.c
>> +++ b/drivers/dpll/dpll_netlink.c
>> @@ -925,7 +925,6 @@ dpll_pin_parent_pin_set(struct dpll_pin *pin, struct nlattr *parent_nest,
>>   			struct netlink_ext_ack *extack)
>>   {
>>   	struct nlattr *tb[DPLL_A_PIN_MAX + 1];
>> -	enum dpll_pin_state state;
>>   	u32 ppin_idx;
>>   	int ret;
>> @@ -936,10 +935,14 @@ dpll_pin_parent_pin_set(struct dpll_pin *pin, struct nlattr *parent_nest,
>>   		return -EINVAL;
>>   	}
>>   	ppin_idx = nla_get_u32(tb[DPLL_A_PIN_PARENT_ID]);
>> -	state = nla_get_u32(tb[DPLL_A_PIN_STATE]);
>> -	ret = dpll_pin_on_pin_state_set(pin, ppin_idx, state, extack);
>> -	if (ret)
>> -		return ret;
>> +
>> +	if (tb[DPLL_A_PIN_STATE]) {
>> +		enum dpll_pin_state state = nla_get_u32(tb[DPLL_A_PIN_STATE]);
>> +
>> +		ret = dpll_pin_on_pin_state_set(pin, ppin_idx, state, extack);
>> +		if (ret)
>> +			return ret;
>> +	}
>>   	return 0;
>>   }
>
>I don't believe that "set" command without set value should return 0
>meaning "request was completed successfully". Maybe it's better to add
>another check like for DPLL_A_PIN_PARENT_ID and fill extack with
>description?

Please see dpll_pin_parent_device_set(). State here is treated exactly
the same as there. It makes sense during set operation to process only
the attributes that are passed. In the future, dpll_pin_parent_pin_set()
can process more attributes, lets be prepared for that.