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

[Jiangshan Yi]

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")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jiangshan Yi <yijiangshan@xxxxxxxxxx>
---
 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 ec483276d753..88505efb42a3 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -1582,9 +1582,14 @@ static int dm_suspend(struct amdgpu_ip_block *ip_block)
 		dc_allow_idle_optimizations(adev->dm.dc, false);

 		dm->cached_dc_state = dc_state_create_copy(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);

 		res = amdgpu_dm_commit_zero_streams(dm->dc);
 		if (res != DC_OK) {
--
2.25.1