linux-hardening - 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 14:39:55 +0300
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        "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,

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.

> 
> 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