drm/amd/display: Fix dangling pointer in connector reset function

amdgpu_dm_connector_funcs_reset() frees the old state before allocating
a new one. If kzalloc() fails, the function returns without updating
the state pointer, leaving a dangling pointer to already freed memory.

Fix this by allocating the new state first. On allocation failure, the
old state remains untouched and the function safely returns.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: e7b07ceef2a6 ("drm/amd/display: Merge amdgpu_dm_crtc and dm_crtc_state")
Signed-off-by: Evgenii Burenchev <evg28bur@yandex.ru>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Link: https://patch.msgid.link/20260629090435.9729-5-evg28bur@yandex.ru
[adjust for movement around current amd-staging-drm-next]
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 20 insertions, 19 deletions

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c
index d4720c5576ce..40688d35bde6 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c
@@ -1786,33 +1786,34 @@ static void amdgpu_dm_connector_destroy(struct drm_connector *connector)
 
 void amdgpu_dm_connector_funcs_reset(struct drm_connector *connector)
 {
-	struct dm_connector_state *state =
+	struct dm_connector_state *old_state =
 		to_dm_connector_state(connector->state);
+	struct dm_connector_state *state;
+
+	state = kzalloc_obj(*state);
+	if (!state)
+		return;
 
 	if (connector->state)
 		__drm_atomic_helper_connector_destroy_state(connector->state);
 
-	kfree(state);
+	kfree(old_state);
 
-	state = kzalloc_obj(*state);
+	__drm_atomic_helper_connector_reset(connector, &state->base);
 
-	if (state) {
-		state->scaling = RMX_OFF;
-		state->underscan_enable = false;
-		state->underscan_hborder = 0;
-		state->underscan_vborder = 0;
-		state->base.max_requested_bpc = 8;
-		state->vcpi_slots = 0;
-		state->pbn = 0;
-
-		if (connector->connector_type == DRM_MODE_CONNECTOR_eDP) {
-			if (amdgpu_dm_abm_level <= 0)
-				state->abm_level = ABM_LEVEL_IMMEDIATE_DISABLE;
-			else
-				state->abm_level = amdgpu_dm_abm_level;
-		}
+	state->scaling = RMX_OFF;
+	state->underscan_enable = false;
+	state->underscan_hborder = 0;
+	state->underscan_vborder = 0;
+	state->base.max_requested_bpc = 8;
+	state->vcpi_slots = 0;
+	state->pbn = 0;
 
-		__drm_atomic_helper_connector_reset(connector, &state->base);
+	if (connector->connector_type == DRM_MODE_CONNECTOR_eDP) {
+		if (amdgpu_dm_abm_level <= 0)
+			state->abm_level = ABM_LEVEL_IMMEDIATE_DISABLE;
+		else
+			state->abm_level = amdgpu_dm_abm_level;
 	}
 }
 EXPORT_IF_KUNIT(amdgpu_dm_connector_funcs_reset);