linux-hardening - Re: [PATCH][next] media: venus: hfi_msgs.h: Replace one-element arrays with flexible-array members

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Date:   Tue, 11 May 2021 10:46:29 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] media: venus: hfi_msgs.h: Replace one-element
 arrays with flexible-array members

Hi all,

Friendly ping:

We are about to be able to globally enable -Warray-bounds and, these are one of
the last out-of-bounds warnings in linux-next.

Could someone take this, please?

Thanks
--
Gustavo

On 2/10/21 18:10, Gustavo A. R. Silva wrote:
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use “flexible array members”[1] for these cases. The older
> style of one-element or zero-length arrays should no longer be used[2].
> 
> Use flexible-array members in struct hfi_msg_sys_property_info_pkt and
> hfi_msg_session_property_info_pkt instead of one-element arrays.
> 
> Also, this helps with the ongoing efforts to enable -Warray-bounds by
> fixing the following warnings:
> 
>   CC [M]  drivers/media/platform/qcom/venus/hfi_msgs.o
> drivers/media/platform/qcom/venus/hfi_msgs.c: In function ‘hfi_sys_property_info’:
> drivers/media/platform/qcom/venus/hfi_msgs.c:246:35: warning: array subscript 1 is above array bounds of ‘u32[1]’ {aka ‘unsigned int[1]’} [-Warray-bounds]
>   246 |  if (req_bytes < 128 || !pkt->data[1] || pkt->num_properties > 1)
>       |                          ~~~~~~~~~^~~
> drivers/media/platform/qcom/venus/hfi_msgs.c: In function ‘hfi_session_prop_info’:
> drivers/media/platform/qcom/venus/hfi_msgs.c:342:62: warning: array subscript 1 is above array bounds of ‘u32[1]’ {aka ‘unsigned int[1]’} [-Warray-bounds]
>   342 |  if (!req_bytes || req_bytes % sizeof(*buf_req) || !pkt->data[1])
>       |                                                     ~~~~~~~~~^~~
> 
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2] https://www.kernel.org/doc/html/v5.9/process/deprecated.html#zero-length-and-one-element-arrays
> 
> Link: https://github.com/KSPP/linux/issues/79
> Link: https://github.com/KSPP/linux/issues/109
> Build-tested-by: <lkp@...el.com>
> Link: https://lore.kernel.org/lkml/6023dd80.MmTeFf8SzwX0iK7%2F%25lkp@intel.com/
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
>  drivers/media/platform/qcom/venus/hfi_msgs.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/platform/qcom/venus/hfi_msgs.h b/drivers/media/platform/qcom/venus/hfi_msgs.h
> index 526d9f5b487b..e2d2ccfbdd24 100644
> --- a/drivers/media/platform/qcom/venus/hfi_msgs.h
> +++ b/drivers/media/platform/qcom/venus/hfi_msgs.h
> @@ -113,7 +113,7 @@ struct hfi_msg_sys_ping_ack_pkt {
>  struct hfi_msg_sys_property_info_pkt {
>  	struct hfi_pkt_hdr hdr;
>  	u32 num_properties;
> -	u32 data[1];
> +	u32 data[];
>  };
>  
>  struct hfi_msg_session_load_resources_done_pkt {
> @@ -233,7 +233,7 @@ struct hfi_msg_session_parse_sequence_header_done_pkt {
>  struct hfi_msg_session_property_info_pkt {
>  	struct hfi_session_hdr_pkt shdr;
>  	u32 num_properties;
> -	u32 data[1];
> +	u32 data[];
>  };
>  
>  struct hfi_msg_session_release_resources_done_pkt {
>