RE: [PATCH v3] drm/amd/display: Fix 'panel_cntl' could be null in 'dcn21_set_backlight_level()'

["Koo, Anthony" <Anthony.Koo@xxxxxxx>]

[AMD Official Use Only - General]

Reviewed-by: Anthony Koo <Anthony.Koo@xxxxxxx>

Thanks,
Anthony

-----Original Message-----
From: SHANMUGAM, SRINIVASAN <SRINIVASAN.SHANMUGAM@xxxxxxx>
Sent: Thursday, February 1, 2024 4:57 AM
To: Siqueira, Rodrigo <Rodrigo.Siqueira@xxxxxxx>; Pillai, Aurabindo <Aurabindo.Pillai@xxxxxxx>; Koo, Anthony <Anthony.Koo@xxxxxxx>
Cc: amd-gfx@xxxxxxxxxxxxxxxxxxxxx; SHANMUGAM, SRINIVASAN <SRINIVASAN.SHANMUGAM@xxxxxxx>; Sun, Yongqiang <Yongqiang.Sun@xxxxxxx>
Subject: [PATCH v3] drm/amd/display: Fix 'panel_cntl' could be null in 'dcn21_set_backlight_level()'

'panel_cntl' structure used to control the display panel could be null, dereferencing it could lead to a null pointer access.

Fixes the below:
drivers/gpu/drm/amd/amdgpu/../display/dc/hwss/dcn21/dcn21_hwseq.c:269 dcn21_set_backlight_level() error: we previously assumed 'panel_cntl' could be null (see line 250)

Fixes: 474ac4a875ca ("drm/amd/display: Implement some asic specific abm call backs.")
Cc: Yongqiang Sun <yongqiang.sun@xxxxxxx>
Cc: Anthony Koo <Anthony.Koo@xxxxxxx>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@xxxxxxx>
Cc: Aurabindo Pillai <aurabindo.pillai@xxxxxxx>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@xxxxxxx>
---
v3:
 - s/u32/uint32_t for consistency (Anthony)

 .../amd/display/dc/hwss/dcn21/dcn21_hwseq.c   | 39 ++++++++++---------
 1 file changed, 20 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/hwss/dcn21/dcn21_hwseq.c b/drivers/gpu/drm/amd/display/dc/hwss/dcn21/dcn21_hwseq.c
index 8323077bba15..5c7f380a84f9 100644
--- a/drivers/gpu/drm/amd/display/dc/hwss/dcn21/dcn21_hwseq.c
+++ b/drivers/gpu/drm/amd/display/dc/hwss/dcn21/dcn21_hwseq.c
@@ -241,34 +241,35 @@ bool dcn21_set_backlight_level(struct pipe_ctx *pipe_ctx,  {
        struct dc_context *dc = pipe_ctx->stream->ctx;
        struct abm *abm = pipe_ctx->stream_res.abm;
+       struct timing_generator *tg = pipe_ctx->stream_res.tg;
        struct panel_cntl *panel_cntl = pipe_ctx->stream->link->panel_cntl;
+       uint32_t otg_inst;
+
+       if (!abm && !tg && !panel_cntl)
+               return false;
+
+       otg_inst = tg->inst;

        if (dc->dc->res_pool->dmcu) {
                dce110_set_backlight_level(pipe_ctx, backlight_pwm_u16_16, frame_ramp);
                return true;
        }

-       if (abm != NULL) {
-               uint32_t otg_inst = pipe_ctx->stream_res.tg->inst;
-
-               if (abm && panel_cntl) {
-                       if (abm->funcs && abm->funcs->set_pipe_ex) {
-                               abm->funcs->set_pipe_ex(abm,
-                                               otg_inst,
-                                               SET_ABM_PIPE_NORMAL,
-                                               panel_cntl->inst,
-                                               panel_cntl->pwrseq_inst);
-                       } else {
-                                       dmub_abm_set_pipe(abm,
-                                                       otg_inst,
-                                                       SET_ABM_PIPE_NORMAL,
-                                                       panel_cntl->inst,
-                                                       panel_cntl->pwrseq_inst);
-                       }
-               }
+       if (abm->funcs && abm->funcs->set_pipe_ex) {
+               abm->funcs->set_pipe_ex(abm,
+                                       otg_inst,
+                                       SET_ABM_PIPE_NORMAL,
+                                       panel_cntl->inst,
+                                       panel_cntl->pwrseq_inst);
+       } else {
+               dmub_abm_set_pipe(abm,
+                                 otg_inst,
+                                 SET_ABM_PIPE_NORMAL,
+                                 panel_cntl->inst,
+                                 panel_cntl->pwrseq_inst);
        }

-       if (abm && abm->funcs && abm->funcs->set_backlight_level_pwm)
+       if (abm->funcs && abm->funcs->set_backlight_level_pwm)
                abm->funcs->set_backlight_level_pwm(abm, backlight_pwm_u16_16,
                        frame_ramp, 0, panel_cntl->inst);
        else
--
2.34.1