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

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Date:   Mon, 17 May 2021 14:01:20 +0300
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.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,

On 5/12/21 7:37 PM, Gustavo A. R. Silva wrote:
> 
> 
> On 5/12/21 06:39, Stanimir Varbanov wrote:
>> Hi,
>>
>> On 5/11/21 6:46 PM, Gustavo A. R. Silva wrote:
>>> 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?
>>
>> This one introduces regressions, so I cannot take it. It needs some more
>> work.
> 
> Please, share with me the errors or warnings you see with this. So, I can
> have an idea of what is going on. Unfortunately, I don't have access to the
> test suite or hardware to test this.

I guess it needs more debugging, but the simple answer is that the
driver refuse to start streaming with this patch.

> 
> Thanks!
> --
> Gustavo
> 
> 
> 
>>>
>>> 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 {
>>>>
>>

-- 
regards,
Stan