drm/amd/display: Fix possible NULL dereference on device remove/driver unload

As part of a cleanup amdgpu_dm_fini() function, which is typically
called when a device is being shut down or a driver is being unloaded

The below error message suggests that there is a potential null pointer
dereference issue with adev->dm.dc.

In the below, line of code where adev->dm.dc is used without a preceding
null check:

for (i = 0; i < adev->dm.dc->caps.max_links; i++) {

To fix this issue, add a null check for adev->dm.dc before this line.

Reported by smatch:
drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c:1959 amdgpu_dm_fini() error: we previously assumed 'adev->dm.dc' could be null (see line 1943)

Fixes: 006c26a0f1c8 ("drm/amd/display: Fix crash on device remove/driver unload")
Cc: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Roman Li <roman.li@amd.com>
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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 367868ad20d7783e09028713b468f38c24d7a20d..a2220d4787fb3aad2d8a3c4e403d3cf732c79724 100644 (file)
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -1955,7 +1955,7 @@ static void amdgpu_dm_fini(struct amdgpu_device *adev)
                                      &adev->dm.dmub_bo_gpu_addr,
                                      &adev->dm.dmub_bo_cpu_addr);
 
-       if (adev->dm.hpd_rx_offload_wq) {
+       if (adev->dm.hpd_rx_offload_wq && adev->dm.dc) {
                for (i = 0; i < adev->dm.dc->caps.max_links; i++) {
                        if (adev->dm.hpd_rx_offload_wq[i].wq) {
                                destroy_workqueue(adev->dm.hpd_rx_offload_wq[i].wq);