RE: [PATCH] drm/amd/display: fix possible buffer overflow relating to secure display

[Liu, HaoPing (Alan)]

[AMD Official Use Only - General]

Reviewed-by: Alan Liu <HaoPing.Liu@xxxxxxx>

Thanks,
Alan

-----Original Message-----
From: Mahfooz, Hamza <Hamza.Mahfooz@xxxxxxx> 
Sent: Thursday, January 12, 2023 2:17 AM
To: amd-gfx@xxxxxxxxxxxxxxxxxxxxx
Cc: Mahfooz, Hamza <Hamza.Mahfooz@xxxxxxx>; Wentland, Harry <Harry.Wentland@xxxxxxx>; Li, Sun peng (Leo) <Sunpeng.Li@xxxxxxx>; Siqueira, Rodrigo <Rodrigo.Siqueira@xxxxxxx>; Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Koenig, Christian <Christian.Koenig@xxxxxxx>; Pan, Xinhui <Xinhui.Pan@xxxxxxx>; David Airlie <airlied@xxxxxxxxx>; Daniel Vetter <daniel@xxxxxxxx>; Lin, Wayne <Wayne.Lin@xxxxxxx>; Pillai, Aurabindo <Aurabindo.Pillai@xxxxxxx>; Li, Roman <Roman.Li@xxxxxxx>; Wu, Hersen <hersenxs.wu@xxxxxxx>; Zuo, Jerry <Jerry.Zuo@xxxxxxx>; Liu, HaoPing (Alan) <HaoPing.Liu@xxxxxxx>; Dhillon, Jasdeep <Jasdeep.Dhillon@xxxxxxx>; Liu, Aaron <Aaron.Liu@xxxxxxx>; dri-devel@xxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
Subject: [PATCH] drm/amd/display: fix possible buffer overflow relating to secure display

It is possible that adev->dm.dc->caps.max_links is greater than AMDGPU_MAX_CRTCS. So, to not potentially access unallocated memory use
adev->mode_info.num_crtc to do the bounds check instead of 
adev->dm.dc->caps.max_links.

Fixes: 278b2b5ba2f2 ("drm/amd/display: Implement multiple secure display")
Fixes: 65a2fbe75cd5 ("drm/amd/display: Fix when disabling secure_display")
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@xxxxxxx>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c     | 2 +-
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c | 8 +++++---
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index b4d60eedbcbf..86a268cc4b21 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -1742,7 +1742,7 @@ static void amdgpu_dm_fini(struct amdgpu_device *adev)
 
 #if defined(CONFIG_DRM_AMD_SECURE_DISPLAY)
 	if (adev->dm.secure_display_ctxs) {
-		for (i = 0; i < adev->dm.dc->caps.max_links; i++) {
+		for (i = 0; i < adev->mode_info.num_crtc; i++) {
 			if (adev->dm.secure_display_ctxs[i].crtc) {
 				flush_work(&adev->dm.secure_display_ctxs[i].notify_ta_work);
 				flush_work(&adev->dm.secure_display_ctxs[i].forward_roi_work);
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c
index 8841c447d0e2..8873ecada27c 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c
@@ -223,7 +223,7 @@ int amdgpu_dm_crtc_configure_crc_source(struct drm_crtc *crtc,  #if defined(CONFIG_DRM_AMD_SECURE_DISPLAY)
 		/* Disable secure_display if it was enabled */
 		if (!enable) {
-			for (i = 0; i < adev->dm.dc->caps.max_links; i++) {
+			for (i = 0; i < adev->mode_info.num_crtc; i++) {
 				if (adev->dm.secure_display_ctxs[i].crtc == crtc) {
 					/* stop ROI update on this crtc */
 					flush_work(&adev->dm.secure_display_ctxs[i].notify_ta_work);
@@ -544,12 +544,14 @@ amdgpu_dm_crtc_secure_display_create_contexts(struct amdgpu_device *adev)
 	struct secure_display_context *secure_display_ctxs = NULL;
 	int i;
 
-	secure_display_ctxs = kcalloc(AMDGPU_MAX_CRTCS, sizeof(struct secure_display_context), GFP_KERNEL);
+	secure_display_ctxs = kcalloc(adev->mode_info.num_crtc,
+				      sizeof(struct secure_display_context),
+				      GFP_KERNEL);
 
 	if (!secure_display_ctxs)
 		return NULL;
 
-	for (i = 0; i < adev->dm.dc->caps.max_links; i++) {
+	for (i = 0; i < adev->mode_info.num_crtc; i++) {
 		INIT_WORK(&secure_display_ctxs[i].forward_roi_work, amdgpu_dm_forward_crc_window);
 		INIT_WORK(&secure_display_ctxs[i].notify_ta_work, amdgpu_dm_crtc_notify_ta_to_read);
 		secure_display_ctxs[i].crtc = &adev->mode_info.crtcs[i]->base;
--
2.38.1