Re: [PATCH][venus-for-next-v5.14] media: venus: hfi_cmds: Fix packet size calculation

[Gustavo A. R. Silva]

On 6/2/21 14:55, Kees Cook wrote:
> On Tue, Jun 01, 2021 at 01:46:16PM -0500, Gustavo A. R. Silva wrote:
>> Now that a one-element array was replaced with a flexible-array member
>> in struct hfi_sys_set_property_pkt, use the struct_size() helper to
>> correctly calculate the packet size.
>>
>> Fixes: 701e10b3fd9f ("media: venus: hfi_cmds.h: Replace one-element array with flexible-array member")
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
>> ---
>> BTW... it seems that a similar problem is present in
>> https://lore.kernel.org/linux-hardening/20210211001044.GA69612@embeddedor/ 
>> and that is what is causing the regression. I will send v2 of that
>> patch, shortly. Thanks.
>>
>>  drivers/media/platform/qcom/venus/hfi_cmds.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/media/platform/qcom/venus/hfi_cmds.c b/drivers/media/platform/qcom/venus/hfi_cmds.c
>> index 11a8347e5f5c..c86279e5d6e8 100644
>> --- a/drivers/media/platform/qcom/venus/hfi_cmds.c
>> +++ b/drivers/media/platform/qcom/venus/hfi_cmds.c
>> @@ -27,7 +27,7 @@ void pkt_sys_idle_indicator(struct hfi_sys_set_property_pkt *pkt, u32 enable)
>>  {
>>  	struct hfi_enable *hfi = (struct hfi_enable *)&pkt->data[1];
>>  
>> -	pkt->hdr.size = sizeof(*pkt) + sizeof(*hfi) + sizeof(u32);
>> +	pkt->hdr.size = struct_size(pkt, data, 2) + sizeof(*hfi);
> 
> I think this should be "1" not "2".
> 
> (i.e. there is a single "data" item, followed by an entire *hfi (which
> starts immediate after data[0]).

Yeah; I see your point. Here I just wanted to preserve the exact same size
as the original code, which turns out has a "benign" off-by-one issue.

I'll fix it up and respin.

Thanks!
--
Gustavo

> 
>>  	pkt->hdr.pkt_type = HFI_CMD_SYS_SET_PROPERTY;
>>  	pkt->num_properties = 1;
>>  	pkt->data[0] = HFI_PROPERTY_SYS_IDLE_INDICATOR;
>> @@ -39,7 +39,7 @@ void pkt_sys_debug_config(struct hfi_sys_set_property_pkt *pkt, u32 mode,
>>  {
>>  	struct hfi_debug_config *hfi;
>>  
>> -	pkt->hdr.size = sizeof(*pkt) + sizeof(*hfi) + sizeof(u32);
>> +	pkt->hdr.size = struct_size(pkt, data, 2) + sizeof(*hfi);
> 
> Same here.
> 
>>  	pkt->hdr.pkt_type = HFI_CMD_SYS_SET_PROPERTY;
>>  	pkt->num_properties = 1;
>>  	pkt->data[0] = HFI_PROPERTY_SYS_DEBUG_CONFIG;
>> @@ -50,7 +50,7 @@ void pkt_sys_debug_config(struct hfi_sys_set_property_pkt *pkt, u32 mode,
>>  
>>  void pkt_sys_coverage_config(struct hfi_sys_set_property_pkt *pkt, u32 mode)
>>  {
>> -	pkt->hdr.size = sizeof(*pkt) + sizeof(u32);
>> +	pkt->hdr.size = struct_size(pkt, data, 2);
> 
> This looks correct.
> 
>>  	pkt->hdr.pkt_type = HFI_CMD_SYS_SET_PROPERTY;
>>  	pkt->num_properties = 1;
>>  	pkt->data[0] = HFI_PROPERTY_SYS_CONFIG_COVERAGE;
>> @@ -116,7 +116,7 @@ void pkt_sys_power_control(struct hfi_sys_set_property_pkt *pkt, u32 enable)
>>  {
>>  	struct hfi_enable *hfi = (struct hfi_enable *)&pkt->data[1];
>>  
>> -	pkt->hdr.size = sizeof(*pkt) + sizeof(*hfi) + sizeof(u32);
>> +	pkt->hdr.size = struct_size(pkt, data, 2) + sizeof(*hfi);
> 
> Also 1.
> 
>>  	pkt->hdr.pkt_type = HFI_CMD_SYS_SET_PROPERTY;
>>  	pkt->num_properties = 1;
>>  	pkt->data[0] = HFI_PROPERTY_SYS_CODEC_POWER_PLANE_CTRL;
>> -- 
>> 2.27.0
>>
>