On 18.02.2022 11:03, Ville Syrjala wrote:
From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Add a variant of drm_mode_copy() that explicitly clears out
the list head of the destination mode. Helpful to guarantee
we don't have stack garbage left in there for on-stack modes.
Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/drm_modes.c | 17 +++++++++++++++++
include/drm/drm_modes.h | 2 ++
2 files changed, 19 insertions(+)
diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index 96b13e36293c..40d4ce4a1da4 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -892,6 +892,23 @@ void drm_mode_copy(struct drm_display_mode *dst, const struct drm_display_mode *
}
EXPORT_SYMBOL(drm_mode_copy);
+/**
+ * drm_mode_init - initialize the mode from another mode
+ * @dst: mode to overwrite
+ * @src: mode to copy
+ *
+ * Copy an existing mode into another mode, zeroing the
+ * list head of the destination mode. Typically used
+ * to guarantee the list head is not left with stack
+ * garbage in on-stack modes.
+ */
+void drm_mode_init(struct drm_display_mode *dst, const struct drm_display_mode *src)
+{
+ memset(dst, 0, sizeof(*dst));
Why not just clear the list head? Or maybe poison it? It would be more
cleaner.
I wonder why there is no such helper in list.h.
Regards
Andrzej
+ drm_mode_copy(dst, src);
+}
+EXPORT_SYMBOL(drm_mode_init);
+
/**
* drm_mode_duplicate - allocate and duplicate an existing mode
* @dev: drm_device to allocate the duplicated mode for
diff --git a/include/drm/drm_modes.h b/include/drm/drm_modes.h
index 29ba4adf0c53..e6e5a588fab1 100644
--- a/include/drm/drm_modes.h
+++ b/include/drm/drm_modes.h
@@ -484,6 +484,8 @@ void drm_mode_set_crtcinfo(struct drm_display_mode *p,
int adjust_flags);
void drm_mode_copy(struct drm_display_mode *dst,
const struct drm_display_mode *src);
+void drm_mode_init(struct drm_display_mode *dst,
+ const struct drm_display_mode *src);
struct drm_display_mode *drm_mode_duplicate(struct drm_device *dev,
const struct drm_display_mode *mode);
bool drm_mode_match(const struct drm_display_mode *mode1,
