[Skiboot] [PATCH] fsp/ipmi: Fix an illegal memory access

[Kamalesh Babulal]

On 07/13/2015 05:32 PM, Neelesh Gupta wrote:
> Hi Kamalesh,
>
> On 07/13/2015 02:59 PM, Kamalesh Babulal wrote:
>> On 07/13/2015 10:36 AM, Neelesh Gupta wrote:
>>> The patch fixes an illegal access to the memory which has been
>>> freed.
>>>
>>> Fixes Coverity defect # 101858
>>>
>>> Signed-off-by: Neelesh Gupta <neelegup at linux.vnet.ibm.com>
>>> ---
>>>  hw/fsp/fsp-ipmi.c |    3 +--
>>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>>
>>> diff --git a/hw/fsp/fsp-ipmi.c b/hw/fsp/fsp-ipmi.c
>>> index e5cd6e2..729ff93 100644
>>> --- a/hw/fsp/fsp-ipmi.c
>>> +++ b/hw/fsp/fsp-ipmi.c
>>> @@ -87,13 +87,12 @@ static void fsp_ipmi_req_complete(struct fsp_msg *msg)
>>>  {
>>>  	uint8_t status = (msg->resp->word1 >> 8) & 0xff;
>>>  	uint32_t length = msg->resp->data.words[0];
>>> -	struct fsp_ipmi_msg *fsp_ipmi_msg;
>>> +	struct fsp_ipmi_msg *fsp_ipmi_msg = msg->user_data;
>>>  	struct ipmi_msg *ipmi_msg;
>>>
>>>  	fsp_freemsg(msg);
>>>
>>>  	if (status != FSP_STATUS_SUCCESS) {
>>> -		fsp_ipmi_msg = msg->user_data;
>>>  		assert(fsp_ipmi_msg == fsp_ipmi.cur_msg);
>>>
>>>  		ipmi_msg = &fsp_ipmi_msg->ipmi_msg;
>> fsp_free(msg) means msg->user_data is also un-allocated. It means
>> fsp_ipmi_msg is pointing
>> to memory which is freed. From the code, I am guessing you need
>> free(msg) before you
>> call fsp_ipmi_send_request(). If my assumption is right, how about below
>> code ?
>
> 'msg->user_data' is a private data to this driver and the driver has to
> take care of it. For instance, 'fsp_ipmi_msg' can only be free'd through
> a backend callback i.e., fsp_ipmi_free_msg() in this driver.
>

Sorry let me re-phrase it better what I meant was, does the code tries
to achieve:

|_ fsp_freemsg(msg)
    |_ fsp_impi_send_request()

If so, it better to move fsp_freemsg(msg) right before calling
fsp_impi_send_request(), as
the data deferenced will be still pointing to valid memory.

>
>> --- a/hw/fsp/fsp-ipmi.c
>> +++ b/hw/fsp/fsp-ipmi.c
>> @@ -90,8 +90,6 @@ static void fsp_ipmi_req_complete(struct fsp_msg *msg)
>>         struct fsp_ipmi_msg *fsp_ipmi_msg;
>>         struct ipmi_msg *ipmi_msg;
>>
>> -       fsp_freemsg(msg);
>> -
>>         if (status != FSP_STATUS_SUCCESS) {
>>                 fsp_ipmi_msg = msg->user_data;
>>                 assert(fsp_ipmi_msg == fsp_ipmi.cur_msg);
>> @@ -111,9 +109,14 @@ static void fsp_ipmi_req_complete(struct fsp_msg *msg)
>>                                   IPMI_NETFN_RETURN_CODE(ipmi_msg->netfn),
>>                                   IPMI_ERR_UNSPECIFIED);
>>
>> +              fsp_freemsg(msg);
>> +
>>                 /* Send the next request in the queue */
>>                 fsp_ipmi_send_request();
>> +              return;
>>         }
>> +
>> +       fsp_freemsg(msg);
>>  }
>>
>>  static int fsp_ipmi_send_request(void)


>

-- 
Cheers,
Kamalesh.