[PATCH 5.15.y] drm/amd/display: check dc_state_create_copy() for NULL in dm_suspend

[Sasha Levin <sashal@kernel.org>]

From: Jiangshan Yi <yijiangshan@kylinos.cn>

[ Upstream commit 015e72cde567d2450e282c2790773463156b2d0a ]

dc_state_create_copy() can return NULL on allocation failure.
dm_suspend() only conditionally skips dm_gpureset_toggle_interrupts()
and continues execution, returning success.  dm_resume() then
dereferences the NULL cached_dc_state in link_enc_cfg_copy() and the
following dc_state->stream_count loop, crashing during GPU reset
recovery.

Return -ENOMEM immediately if the copy fails, so the caller aborts
suspend instead of leaving a NULL cached state for resume.

Fixes: 8092aa3ab8f7 ("drm/amd/display: Add null checker before passing variables")
Reviewed-by: George Zhang <george.zhang@amd.com>
Signed-off-by: Jiangshan Yi <yijiangshan@kylinos.cn>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 84b6d7932fdd2857795a257f9f258562a3cddcab)
Cc: stable@vger.kernel.org
[ sashal: Adapted dc_state_create_copy() usage to dc_copy_state(). ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 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 4530d22139355..288ef18e70d05 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -2440,9 +2440,14 @@ static int dm_suspend(void *handle)
 #endif
 
 		dm->cached_dc_state = dc_copy_state(dm->dc->current_state);
+		if (!dm->cached_dc_state) {
+			drm_err(adev_to_drm(adev),
+				"Failed to allocate cached DC state during suspend\n");
+			mutex_unlock(&dm->dc_lock);
+			return -ENOMEM;
+		}
 
-		if (dm->cached_dc_state)
-			dm_gpureset_toggle_interrupts(adev, dm->cached_dc_state, false);
+		dm_gpureset_toggle_interrupts(adev, dm->cached_dc_state, false);
 
 		amdgpu_dm_commit_zero_streams(dm->dc);
 
-- 
2.53.0