Re: [PATCH v2] [next] drm/amdgpu: Replace one-element array with flexible-array member

[Alex Deucher]

Applied.  Thanks!

Alex

On Fri, Oct 28, 2022 at 9:31 PM Paulo Miguel Almeida
 wrote:
>
> One-element arrays are deprecated, and we are replacing them with
> flexible array members instead. So, replace one-element array with
> flexible-array member in struct _ATOM_FAKE_EDID_PATCH_RECORD and
> refactor the rest of the code accordingly.
>
> Important to mention is that doing a build before/after this patch
> results in no binary output differences.
>
> This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
> routines on memcpy() and help us make progress towards globally
> enabling -fstrict-flex-arrays=3 [1].
>
> Link: https://github.com/KSPP/linux/issues/79
> Link: https://github.com/KSPP/linux/issues/238
> Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836 [1]
>
> Signed-off-by: Paulo Miguel Almeida 
> ---
> Changelog:
>
> v2: no binary output differences patch; report binary changes findings
> on commit log. Res: Kees Cook
> v1: https://lore.kernel.org/lkml/y1tkwdwpup+ud...@mail.google.com/
> ---
>  drivers/gpu/drm/amd/amdgpu/atombios_encoders.c | 7 +--
>  drivers/gpu/drm/amd/include/atombios.h | 2 +-
>  2 files changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c 
> b/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c
> index 6be9ac2b9c5b..18ae9433e463 100644
> --- a/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c
> +++ b/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c
> @@ -2081,8 +2081,11 @@ amdgpu_atombios_encoder_get_lcd_info(struct 
> amdgpu_encoder *encoder)
> }
> }
> record += 
> fake_edid_record->ucFakeEDIDLength ?
> -   
> fake_edid_record->ucFakeEDIDLength + 2 :
> -   
> sizeof(ATOM_FAKE_EDID_PATCH_RECORD);
> + 
> struct_size(fake_edid_record,
> + 
> ucFakeEDIDString,
> + 
> fake_edid_record->ucFakeEDIDLength) :
> + /* empty fake edid record 
> must be 3 bytes long */
> + 
> sizeof(ATOM_FAKE_EDID_PATCH_RECORD) + 1;
> break;
> case LCD_PANEL_RESOLUTION_RECORD_TYPE:
> panel_res_record = 
> (ATOM_PANEL_RESOLUTION_PATCH_RECORD *)record;
> diff --git a/drivers/gpu/drm/amd/include/atombios.h 
> b/drivers/gpu/drm/amd/include/atombios.h
> index 15943bc21bc5..b5b1d073f8e2 100644
> --- a/drivers/gpu/drm/amd/include/atombios.h
> +++ b/drivers/gpu/drm/amd/include/atombios.h
> @@ -4107,7 +4107,7 @@ typedef struct _ATOM_FAKE_EDID_PATCH_RECORD
>  {
>UCHAR ucRecordType;
>UCHAR ucFakeEDIDLength;   // = 128 means EDID length is 128 bytes, 
> otherwise the EDID length = ucFakeEDIDLength*128
> -  UCHAR ucFakeEDIDString[1];// This actually has ucFakeEdidLength 
> elements.
> +  UCHAR ucFakeEDIDString[]; // This actually has ucFakeEdidLength 
> elements.
>  } ATOM_FAKE_EDID_PATCH_RECORD;
>
>  typedef struct  _ATOM_PANEL_RESOLUTION_PATCH_RECORD
> --
> 2.37.3
>

[PATCH v2] [next] drm/amdgpu: Replace one-element array with flexible-array member

[Paulo Miguel Almeida]

One-element arrays are deprecated, and we are replacing them with
flexible array members instead. So, replace one-element array with
flexible-array member in struct _ATOM_FAKE_EDID_PATCH_RECORD and
refactor the rest of the code accordingly.

Important to mention is that doing a build before/after this patch
results in no binary output differences.

This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
routines on memcpy() and help us make progress towards globally
enabling -fstrict-flex-arrays=3 [1].

Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/238
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836 [1]

Signed-off-by: Paulo Miguel Almeida 
---
Changelog:

v2: no binary output differences patch; report binary changes findings
on commit log. Res: Kees Cook
v1: https://lore.kernel.org/lkml/y1tkwdwpup+ud...@mail.google.com/
---
 drivers/gpu/drm/amd/amdgpu/atombios_encoders.c | 7 +--
 drivers/gpu/drm/amd/include/atombios.h | 2 +-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c 
b/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c
index 6be9ac2b9c5b..18ae9433e463 100644
--- a/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c
+++ b/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c
@@ -2081,8 +2081,11 @@ amdgpu_atombios_encoder_get_lcd_info(struct 
amdgpu_encoder *encoder)
}
}
record += 
fake_edid_record->ucFakeEDIDLength ?
-   
fake_edid_record->ucFakeEDIDLength + 2 :
-   
sizeof(ATOM_FAKE_EDID_PATCH_RECORD);
+ struct_size(fake_edid_record,
+ ucFakeEDIDString,
+ 
fake_edid_record->ucFakeEDIDLength) :
+ /* empty fake edid record 
must be 3 bytes long */
+ 
sizeof(ATOM_FAKE_EDID_PATCH_RECORD) + 1;
break;
case LCD_PANEL_RESOLUTION_RECORD_TYPE:
panel_res_record = 
(ATOM_PANEL_RESOLUTION_PATCH_RECORD *)record;
diff --git a/drivers/gpu/drm/amd/include/atombios.h 
b/drivers/gpu/drm/amd/include/atombios.h
index 15943bc21bc5..b5b1d073f8e2 100644
--- a/drivers/gpu/drm/amd/include/atombios.h
+++ b/drivers/gpu/drm/amd/include/atombios.h
@@ -4107,7 +4107,7 @@ typedef struct _ATOM_FAKE_EDID_PATCH_RECORD
 {
   UCHAR ucRecordType;
   UCHAR ucFakeEDIDLength;   // = 128 means EDID length is 128 bytes, 
otherwise the EDID length = ucFakeEDIDLength*128
-  UCHAR ucFakeEDIDString[1];// This actually has ucFakeEdidLength elements.
+  UCHAR ucFakeEDIDString[]; // This actually has ucFakeEdidLength elements.
 } ATOM_FAKE_EDID_PATCH_RECORD;
 
 typedef struct  _ATOM_PANEL_RESOLUTION_PATCH_RECORD
-- 
2.37.3