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

[Kees Cook <keescook@chromium.org>]

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@kernel.org>
> ---
> 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]).

>  	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
> 

-- 
Kees Cook