drm/radeon: Replace one-element array with flexible-array member

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.

It's worth mentioning 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/239
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/radeon/atombios.h b/drivers/gpu/drm/radeon/atombios.h
index da35a97..235e59b 100644 (file)
--- a/drivers/gpu/drm/radeon/atombios.h
+++ b/drivers/gpu/drm/radeon/atombios.h
@@ -3615,7 +3615,7 @@ typedef struct _ATOM_FAKE_EDID_PATCH_RECORD
 {
   UCHAR ucRecordType;
   UCHAR ucFakeEDIDLength;
-  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

diff --git a/drivers/gpu/drm/radeon/radeon_atombios.c b/drivers/gpu/drm/radeon/radeon_atombios.c
index 204127b..4ad5a32 100644 (file)
--- a/drivers/gpu/drm/radeon/radeon_atombios.c
+++ b/drivers/gpu/drm/radeon/radeon_atombios.c
@@ -1727,8 +1727,11 @@ struct radeon_encoder_atom_dig *radeon_atombios_get_lvds_info(struct
                                                }
                                        }
                                        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;