drm/amd/display: Fix potential null pointer dereference in dc_dmub_srv

Fixes potential null pointer dereference warnings in the
dc_dmub_srv_cmd_list_queue_execute() and dc_dmub_srv_is_hw_pwr_up()
functions.

In both functions, the 'dc_dmub_srv' variable was being dereferenced
before it was checked for null. This could lead to a null pointer
dereference if 'dc_dmub_srv' is null. The fix is to check if
'dc_dmub_srv' is null before dereferencing it.

Thus moving the null checks for 'dc_dmub_srv' to the beginning of the
functions to ensure that 'dc_dmub_srv' is not null when it is
dereferenced.

Found by smatch & thus fixing the below:
drivers/gpu/drm/amd/amdgpu/../display/dc/dc_dmub_srv.c:133 dc_dmub_srv_cmd_list_queue_execute() warn: variable dereferenced before check 'dc_dmub_srv' (see line 128)
drivers/gpu/drm/amd/amdgpu/../display/dc/dc_dmub_srv.c:1167 dc_dmub_srv_is_hw_pwr_up() warn: variable dereferenced before check 'dc_dmub_srv' (see line 1164)

Fixes: 028bac583449 ("drm/amd/display: decouple dmcub execution to reduce lock granularity")
Fixes: 65138eb72e1f ("drm/amd/display: Add DCN35 DMUB")
Cc: JinZe.Xu <jinze.xu@amd.com>
Cc: Hersen Wu <hersenxs.wu@amd.com>
Cc: Josip Pavic <josip.pavic@amd.com>
Cc: Roman Li <roman.li@amd.com>
Cc: Qingqing Zhuo <Qingqing.Zhuo@amd.com>
Cc: Harry Wentland <Harry.Wentland@amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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 2b79a0e5638e1b757ea3d3527add517db139552e..363d522603a21744c02e3e3497a2907862b02fd1 100644 (file)
--- 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_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;
@@ -133,6 +133,7 @@ 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++) {
@@ -1161,7 +1162,7 @@ void dc_dmub_srv_subvp_save_surf_addr(const struct dc_dmub_srv *dc_dmub_srv, con
 
 bool dc_dmub_srv_is_hw_pwr_up(struct dc_dmub_srv *dc_dmub_srv, bool wait)
 {
-       struct dc_context *dc_ctx = dc_dmub_srv->ctx;
+       struct dc_context *dc_ctx;
        enum dmub_status status;
 
        if (!dc_dmub_srv || !dc_dmub_srv->dmub)
@@ -1170,6 +1171,8 @@ bool dc_dmub_srv_is_hw_pwr_up(struct dc_dmub_srv *dc_dmub_srv, bool wait)
        if (dc_dmub_srv->ctx->dc->debug.dmcub_emulation)
                return true;
 
+       dc_ctx = dc_dmub_srv->ctx;
+
        if (wait) {
                if (dc_dmub_srv->ctx->dc->debug.disable_timeout) {
                        do {