linux-kernel - [PATCH next] drm/amd/display: Fix possible NULL dereference in dc_dmub_srv_cmd_run

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Date:   Wed, 26 Apr 2023 12:24:12 -0700
From:   Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     error27@...il.com, kernel-janitors@...r.kernel.org,
        Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>,
        Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Alvin Lee <Alvin.Lee2@....com>, Jun Lei <Jun.Lei@....com>,
        Qingqing Zhuo <qingqing.zhuo@....com>,
        Josip Pavic <Josip.Pavic@....com>,
        Max Tseng <Max.Tseng@....com>, Eric Yang <Eric.Yang2@....com>,
        Nicholas Kazlauskas <Nicholas.Kazlauskas@....com>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH next] drm/amd/display: Fix possible NULL dereference in dc_dmub_srv_cmd_run_list()

We have a NULL check for 'dc_dmub_srv' in dc_dmub_srv_cmd_run_list()
but we are dereferencing it before checking.

Fix this moving the dereference next to NULL check.

This issue is found with Smatch(static analysis tool).

Fixes: e97cc04fe0fb ("drm/amd/display: refactor dmub commands into single function")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.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 d15ec32243e2..62d3473c32bc 100644
--- a/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c
+++ b/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c
@@ -125,7 +125,7 @@ bool dc_dmub_srv_cmd_run(struct dc_dmub_srv *dc_dmub_srv, union dmub_rb_cmd *cmd
 
 bool dc_dmub_srv_cmd_run_list(struct dc_dmub_srv *dc_dmub_srv, unsigned int count, union dmub_rb_cmd *cmd_list, enum dm_dmub_wait_type wait_type)
 {
-	struct dc_context *dc_ctx = dc_dmub_srv->ctx;
+	struct dc_context *dc_ctx;
 	struct dmub_srv *dmub;
 	enum dmub_status status;
 	int i;
@@ -133,6 +133,7 @@ bool dc_dmub_srv_cmd_run_list(struct dc_dmub_srv *dc_dmub_srv, unsigned int coun
 	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++) {
-- 
2.38.1