From 27d471af77c7f953584dc95e975bd2697f0f4d76 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 12:04:03 +0200
Subject: drm: Use drm_mode_copy()
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Git-commit: a3342f4d5af16888e385980a4bea4cc195c36bc0
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

struct drm_display_mode embeds a list head, so overwriting
the full struct with another one will corrupt the list
(if the destination mode is on a list). Use drm_mode_copy()
instead which explicitly preserves the list head of
the destination mode.

Even if we know the destination mode is not on any list
using drm_mode_copy() seems decent as it sets a good
example. Bad examples of not using it might eventually
get copied into code where preserving the list head
actually matters.

Obviously one case not covered here is when the mode
itself is embedded in a larger structure and the whole
structure is copied. But if we are careful when copying
into modes embedded in structures I think we can be a
little more reassured that bogus list heads haven't been
propagated in.

@is_mode_copy@
@@
drm_mode_copy(...)
{
...
}

@depends on !is_mode_copy@
struct drm_display_mode *mode;
expression E, S;
@@
(
- *mode = E
+ drm_mode_copy(mode, &E)
|
- memcpy(mode, E, S)
+ drm_mode_copy(mode, E)
)

@depends on !is_mode_copy@
struct drm_display_mode mode;
expression E;
@@
(
- mode = E
+ drm_mode_copy(&mode, &E)
|
- memcpy(&mode, E, S)
+ drm_mode_copy(&mode, E)
)

@@
struct drm_display_mode *mode;
@@
- &*mode
+ mode

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220218100403.7028-23-ville.syrjala@linux.intel.com
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/drm_crtc_helper.c | 4 ++--
 drivers/gpu/drm/drm_vblank.c      | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
index a34aa009725f..b632825654a9 100644
--- a/drivers/gpu/drm/drm_crtc_helper.c
+++ b/drivers/gpu/drm/drm_crtc_helper.c
@@ -305,7 +305,7 @@ bool drm_crtc_helper_set_mode(struct drm_crtc *crtc,
 	/* Update crtc values up front so the driver can rely on them for mode
 	 * setting.
 	 */
-	crtc->mode = *mode;
+	drm_mode_copy(&crtc->mode, mode);
 	crtc->x = x;
 	crtc->y = y;
 
@@ -341,7 +341,7 @@ bool drm_crtc_helper_set_mode(struct drm_crtc *crtc,
 	}
 	DRM_DEBUG_KMS("[CRTC:%d:%s]\n", crtc->base.id, crtc->name);
 
-	crtc->hwmode = *adjusted_mode;
+	drm_mode_copy(&crtc->hwmode, adjusted_mode);
 
 	/* Prepare the encoders and CRTCs before setting the mode. */
 	drm_for_each_encoder(encoder, dev) {
diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index b701cda86d0c..2ff31717a3de 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -644,7 +644,7 @@ void drm_calc_timestamping_constants(struct drm_crtc *crtc,
 
 	vblank->linedur_ns  = linedur_ns;
 	vblank->framedur_ns = framedur_ns;
-	vblank->hwmode = *mode;
+	drm_mode_copy(&vblank->hwmode, mode);
 
 	drm_dbg_core(dev,
 		     "crtc %u: hwmode: htotal %d, vtotal %d, vdisplay %d\n",
-- 
2.38.1