[PATCH] drm/amd/display: fix a possible NULL dereference bug

[Harshit Mogalapalli]

Smatch warns:
        drivers/gpu/drm/amd/amdgpu/../display/dc/dc_dmub_srv.c:136
        dc_dmub_srv_cmd_list_queue_execute() warn: variable dereferenced
        before check 'dc_dmub_srv' (see line 131)

Fix this by moving the dereference "dc_dmub_srv->ctx" after the NULL check.

Fixes: 028bac583449 ("drm/amd/display: decouple dmcub execution to reduce lock 
granularity")
Reported-by: kernel test robot <l...@intel.com>
Reported-by: Dan Carpenter <erro...@gmail.com>
Closes: https://lore.kernel.org/r/202311141141.golapxd5-...@intel.com/
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapa...@oracle.com>
---
Only compile tested
---
 drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c 
b/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c
index 0bc32537e2eb..a4bd46ec6da4 100644
--- a/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c
+++ b/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c
@@ -128,7 +128,7 @@ bool dc_dmub_srv_cmd_list_queue_execute(struct dc_dmub_srv 
*dc_dmub_srv,
                unsigned int count,
                union dmub_rb_cmd *cmd_list)
 {
-       struct dc_context *dc_ctx = dc_dmub_srv->ctx;
+       struct dc_context *dc_ctx;
        struct dmub_srv *dmub;
        enum dmub_status status;
        int i;
@@ -136,6 +136,7 @@ bool dc_dmub_srv_cmd_list_queue_execute(struct dc_dmub_srv 
*dc_dmub_srv,
        if (!dc_dmub_srv || !dc_dmub_srv->dmub)
                return false;
 
+       dc_ctx = dc_dmub_srv->ctx;
        dmub = dc_dmub_srv->dmub;
 
        for (i = 0 ; i < count; i++) {
-- 
2.39.3