linux-hardening - Re: [PATCH][next] drm/nouveau: Avoid -Wflex-array-member-not-at-end warning

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Message-ID: <30530165-0ea9-4f02-9d8c-e8abc9eda5a7@kernel.org>
Date: Fri, 13 Sep 2024 12:23:38 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 Karol Herbst <kherbst@...hat.com>, Lyude Paul <lyude@...hat.com>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
 dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] drm/nouveau: Avoid -Wflex-array-member-not-at-end
 warning

Hi,

On 9/13/24 10:09 AM, Gustavo A. R. Silva wrote:
> Hi all,
> 
> Friendly ping: who can take this, please? 🙂

Usually, that's me. But I thought you might want to send a v2 based on Kees'
comments?

- Danilo

> 
> Thanks
> -Gustavo
> 
> On 21/08/24 22:16, Gustavo A. R. Silva wrote:
>> Use the `DEFINE_RAW_FLEX()` helper for an on-stack definition of
>> a flexible structure where the size of the flexible-array member
>> is known at compile-time, and refactor the rest of the code,
>> accordingly.
>>
>> So, with this, fix the following warning:
>>
>> drivers/gpu/drm/nouveau/dispnv50/disp.c:779:47: warning: structure containing 
>> a flexible array member is not at the end of another structure 
>> [-Wflex-array-member-not-at-end]
>>
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
>> ---
>>   drivers/gpu/drm/nouveau/dispnv50/disp.c | 20 +++++++++-----------
>>   1 file changed, 9 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c 
>> b/drivers/gpu/drm/nouveau/dispnv50/disp.c
>> index eed579a6c858..ddddc69640be 100644
>> --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
>> +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
>> @@ -774,11 +774,9 @@ nv50_hdmi_enable(struct drm_encoder *encoder, struct 
>> nouveau_crtc *nv_crtc,
>>       struct drm_hdmi_info *hdmi = &nv_connector->base.display_info.hdmi;
>>       union hdmi_infoframe infoframe = { 0 };
>>       const u8 rekey = 56; /* binary driver, and tegra, constant */
>> +    DEFINE_RAW_FLEX(struct nvif_outp_infoframe_v0, args, data, 17);
>> +    const u8 data_len = 17; /* same length as in DEFINE_RAW_FLEX above. */
>>       u32 max_ac_packet;
>> -    struct {
>> -        struct nvif_outp_infoframe_v0 infoframe;
>> -        u8 data[17];
>> -    } args = { 0 };
>>       int ret, size;
>>       max_ac_packet  = mode->htotal - mode->hdisplay;
>> @@ -815,29 +813,29 @@ nv50_hdmi_enable(struct drm_encoder *encoder, struct 
>> nouveau_crtc *nv_crtc,
>>           return;
>>       /* AVI InfoFrame. */
>> -    args.infoframe.version = 0;
>> -    args.infoframe.head = nv_crtc->index;
>> +    args->version = 0;
>> +    args->head = nv_crtc->index;
>>       if (!drm_hdmi_avi_infoframe_from_display_mode(&infoframe.avi, 
>> &nv_connector->base, mode)) {
>>           drm_hdmi_avi_infoframe_quant_range(&infoframe.avi, 
>> &nv_connector->base, mode,
>>                              HDMI_QUANTIZATION_RANGE_FULL);
>> -        size = hdmi_infoframe_pack(&infoframe, args.data, 
>> ARRAY_SIZE(args.data));
>> +        size = hdmi_infoframe_pack(&infoframe, args->data, data_len);
>>       } else {
>>           size = 0;
>>       }
>> -    nvif_outp_infoframe(&nv_encoder->outp, NVIF_OUTP_INFOFRAME_V0_AVI, 
>> &args.infoframe, size);
>> +    nvif_outp_infoframe(&nv_encoder->outp, NVIF_OUTP_INFOFRAME_V0_AVI, args, 
>> size);
>>       /* Vendor InfoFrame. */
>> -    memset(&args.data, 0, sizeof(args.data));
>> +    memset(args->data, 0, data_len);
>>       if (!drm_hdmi_vendor_infoframe_from_display_mode(&infoframe.vendor.hdmi,
>>                                &nv_connector->base, mode))
>> -        size = hdmi_infoframe_pack(&infoframe, args.data, 
>> ARRAY_SIZE(args.data));
>> +        size = hdmi_infoframe_pack(&infoframe, args->data, data_len);
>>       else
>>           size = 0;
>> -    nvif_outp_infoframe(&nv_encoder->outp, NVIF_OUTP_INFOFRAME_V0_VSI, 
>> &args.infoframe, size);
>> +    nvif_outp_infoframe(&nv_encoder->outp, NVIF_OUTP_INFOFRAME_V0_VSI, args, 
>> size);
>>       nv_encoder->hdmi.enabled = true;
>>   }
>