From 588a70177df3b1777484267584ef38ab2ca899a2 Mon Sep 17 00:00:00 2001
From: Zhou Qingyang <zhou1615@umn.edu>
Date: Tue, 25 Jan 2022 00:57:29 +0800
Subject: [PATCH] drm/amd/display: Fix a NULL pointer dereference in amdgpu_dm_connector_add_common_modes()
Git-commit: 588a70177df3b1777484267584ef38ab2ca899a2
Patch-mainline: v5.18-rc1
References: git-fixes

In amdgpu_dm_connector_add_common_modes(), amdgpu_dm_create_common_mode()
is assigned to mode and is passed to drm_mode_probed_add() directly after
that. drm_mode_probed_add() passes &mode->head to list_add_tail(), and
there is a dereference of it in list_add_tail() without recoveries, which
could lead to NULL pointer dereference on failure of
amdgpu_dm_create_common_mode().

Fix this by adding a NULL check of mode.

This bug was found by a static analyzer.

Builds with 'make allyesconfig' show no new warnings,
and our static analyzer no longer warns about this code.

Fixes: e7b07ceef2a6 ("drm/amd/display: Merge amdgpu_dm_types and amdgpu_dm")
Signed-off-by: Zhou Qingyang <zhou1615@umn.edu>
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 | 3 +++
 1 file changed, 3 insertions(+)

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 44f4d862a022..e6ff40fdf18b 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -8138,6 +8138,9 @@ static void amdgpu_dm_connector_add_common_modes(struct drm_encoder *encoder,
 		mode = amdgpu_dm_create_common_mode(encoder,
 				common_modes[i].name, common_modes[i].w,
 				common_modes[i].h);
+		if (!mode)
+			continue;
+
 		drm_mode_probed_add(connector, mode);
 		amdgpu_dm_connector->num_modes++;
 	}
-- 
2.31.1