From 277b73d0fb0632f20e30893e225f04b2d4c76e6b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
Date: Fri, 18 Feb 2022 12:03:42 +0200
Subject: drm: Add drm_mode_init()
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Git-commit: 2d3eec8970335148278a6e350bc4840374f06471
Patch-mainline: v5.19-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

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@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220218100403.7028-2-ville.syrjala@linux.intel.com
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 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 3f819c7a021b..6e7e10f16ec0 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -941,6 +941,23 @@ 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));
+	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 2fa6b2c33b3f..a80ae9639e96 100644
--- a/include/drm/drm_modes.h
+++ b/include/drm/drm_modes.h
@@ -492,6 +492,8 @@ 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,
-- 
2.38.1