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

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Date:   Wed, 12 May 2021 11:37:49 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     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



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.

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 {
>>>
>