From af22d6a869cc26b519bfdcd54293c53f2e491870 Mon Sep 17 00:00:00 2001
From: Hamza Mahfooz <hamza.mahfooz@amd.com>
Date: Wed, 21 Jun 2023 15:19:05 -0400
Subject: [PATCH] drm/amd/display: perform a bounds check before filling dirty rectangles
Git-commit: af22d6a869cc26b519bfdcd54293c53f2e491870
Patch-mainline: v6.5-rc1
References: git-fixes

Currently, it is possible for us to access memory that we shouldn't.
Since, we acquire (possibly dangling) pointers to dirty rectangles
before doing a bounds check to make sure we can actually accommodate the
number of dirty rectangles userspace has requested to fill. This issue
is especially evident if a compositor requests both MPO and damage clips
at the same time, in which case I have observed a soft-hang. So, to
avoid this issue, perform the bounds check before filling a single dirty
rectangle and WARN() about it, if it is ever attempted in
fill_dc_dirty_rect().

Cc: stable@vger.kernel.org # 6.1+
Fixes: 30ebe41582d1 ("drm/amd/display: add FB_DAMAGE_CLIPS support")
Reviewed-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |   13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4907,11 +4907,7 @@ static inline void fill_dc_dirty_rect(st
 				      int32_t y, int32_t width, int32_t height,
 				      int *i, bool ffu)
 {
-	if (*i > DC_MAX_DIRTY_RECTS)
-		return;
-
-	if (*i == DC_MAX_DIRTY_RECTS)
-		goto out;
+	WARN_ON(*i >= DC_MAX_DIRTY_RECTS);
 
 	dirty_rect->x = x;
 	dirty_rect->y = y;
@@ -4927,7 +4923,6 @@ static inline void fill_dc_dirty_rect(st
 			"[PLANE:%d] PSR SU dirty rect at (%d, %d) size (%d, %d)",
 			plane->base.id, x, y, width, height);
 
-out:
 	(*i)++;
 }
 
@@ -5009,6 +5004,9 @@ static void fill_dc_dirty_rects(struct d
 		new_plane_state->plane->base.id,
 		bb_changed, fb_changed, num_clips);
 
+	if ((num_clips + (bb_changed ? 2 : 0)) > DC_MAX_DIRTY_RECTS)
+		goto ffu;
+
 	if (bb_changed) {
 		fill_dc_dirty_rect(new_plane_state->plane, &dirty_rects[i],
 				   new_plane_state->crtc_x,
@@ -5038,9 +5036,6 @@ static void fill_dc_dirty_rects(struct d
 				   new_plane_state->crtc_h, &i, false);
 	}
 
-	if (i > DC_MAX_DIRTY_RECTS)
-		goto ffu;
-
 	flip_addrs->dirty_rect_count = i;
 	return;