From ab30de3673d5d92bc0fd5005e70dac61a808e614 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 12:04:00 +0200
Subject: drm/i915: Use drm_mode_copy()
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Git-commit: 1c7cea157912ec8229b116c9274a18653689e193
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/20220218100403.7028-20-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/i915/display/intel_display.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 6817a3dcf72b..7aee15ee49bf 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -5571,8 +5571,10 @@ intel_crtc_copy_uapi_to_hw_state_modeset(struct intel_atomic_state *state,
 
 	crtc_state->hw.enable = crtc_state->uapi.enable;
 	crtc_state->hw.active = crtc_state->uapi.active;
-	crtc_state->hw.mode = crtc_state->uapi.mode;
-	crtc_state->hw.adjusted_mode = crtc_state->uapi.adjusted_mode;
+	drm_mode_copy(&crtc_state->hw.mode,
+		      &crtc_state->uapi.mode);
+	drm_mode_copy(&crtc_state->hw.adjusted_mode,
+		      &crtc_state->uapi.adjusted_mode);
 	crtc_state->hw.scaling_filter = crtc_state->uapi.scaling_filter;
 
 	intel_crtc_copy_uapi_to_hw_state_nomodeset(state, crtc);
@@ -5652,9 +5654,12 @@ copy_bigjoiner_crtc_state_modeset(struct intel_atomic_state *state,
 	memset(&slave_crtc_state->hw, 0, sizeof(slave_crtc_state->hw));
 	slave_crtc_state->hw.enable = master_crtc_state->hw.enable;
 	slave_crtc_state->hw.active = master_crtc_state->hw.active;
-	slave_crtc_state->hw.mode = master_crtc_state->hw.mode;
-	slave_crtc_state->hw.pipe_mode = master_crtc_state->hw.pipe_mode;
-	slave_crtc_state->hw.adjusted_mode = master_crtc_state->hw.adjusted_mode;
+	drm_mode_copy(&slave_crtc_state->hw.mode,
+		      &master_crtc_state->hw.mode);
+	drm_mode_copy(&slave_crtc_state->hw.pipe_mode,
+		      &master_crtc_state->hw.pipe_mode);
+	drm_mode_copy(&slave_crtc_state->hw.adjusted_mode,
+		      &master_crtc_state->hw.adjusted_mode);
 	slave_crtc_state->hw.scaling_filter = master_crtc_state->hw.scaling_filter;
 
 	copy_bigjoiner_crtc_state_nomodeset(state, slave_crtc);
-- 
2.38.1