linux-hardening - Re: [PATCH][next] media: venus: hfi_cmds.h: Replace one-element array with flexible-array member

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Message-ID: <6081fb66-7f43-cab4-b7ff-ce4b291b8865@embeddedor.com>
Date:   Tue, 11 May 2021 10:44:27 -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_cmds.h: Replace one-element array
 with flexible-array member

Hi all,

Friendly ping:

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

Could someone take this, please?

Thanks
--
Gustavo

On 2/10/21 16:57, 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 member in struct hfi_sys_set_property_pkt instead of
> one-element array.
> 
> Also, this helps with the ongoing efforts to enable -Warray-bounds and
> fix the following warnings:
> 
> drivers/media/platform/qcom/venus/hfi_cmds.c: In function ‘pkt_sys_coverage_config’:
> drivers/media/platform/qcom/venus/hfi_cmds.c:57:11: warning: array subscript 1 is above array bounds of ‘u32[1]’ {aka ‘unsigned int[1]’} [-Warray-bounds]
>    57 |  pkt->data[1] = mode;
>       |  ~~~~~~~~~^~~
> 
> [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: kernel test robot <lkp@...el.com>
> Link: https://lore.kernel.org/lkml/602416da.iZqae7Dbk7nyl6OY%25lkp@intel.com/
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
>  drivers/media/platform/qcom/venus/hfi_cmds.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/qcom/venus/hfi_cmds.h b/drivers/media/platform/qcom/venus/hfi_cmds.h
> index 83705e237f1c..327ed90a2788 100644
> --- a/drivers/media/platform/qcom/venus/hfi_cmds.h
> +++ b/drivers/media/platform/qcom/venus/hfi_cmds.h
> @@ -68,7 +68,7 @@ struct hfi_sys_release_resource_pkt {
>  struct hfi_sys_set_property_pkt {
>  	struct hfi_pkt_hdr hdr;
>  	u32 num_properties;
> -	u32 data[1];
> +	u32 data[];
>  };
>  
>  struct hfi_sys_get_property_pkt {
>