[PATCH v2] drm/amd/display: Add NULL test for 'timing generator' in 'dcn21_set_pipe()'

[SRINIVASAN SHANMUGAM]

On 2/13/2024 12:07 AM, Kees Cook wrote:
> On Thu, Feb 01, 2024 at 03:28:45PM +0530, Srinivasan Shanmugam wrote:
>> In "u32 otg_inst = pipe_ctx->stream_res.tg->inst;"
>> pipe_ctx->stream_res.tg could be NULL, it is relying on the caller to
>> ensure the tg is not NULL.
>>
>> Fixes: 474ac4a875ca ("drm/amd/display: Implement some asic specific abm call backs.")
>> Cc: Yongqiang Sun <yongqiang.sun at amd.com>
>> Cc: Anthony Koo <Anthony.Koo at amd.com>
>> Cc: Rodrigo Siqueira <Rodrigo.Siqueira at amd.com>
>> Cc: Aurabindo Pillai <aurabindo.pillai at amd.com>
>> Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam at amd.com>
>> ---
>> v2:
>>    - s/u32/uint32_t for consistency (Anthony)
>>
>>   .../amd/display/dc/hwss/dcn21/dcn21_hwseq.c   | 24 +++++++++++--------
>>   1 file changed, 14 insertions(+), 10 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 8e88dcaf88f5..8323077bba15 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
>> @@ -206,28 +206,32 @@ void dcn21_set_abm_immediate_disable(struct pipe_ctx *pipe_ctx)
>>   void dcn21_set_pipe(struct pipe_ctx *pipe_ctx)
>>   {
>>   	struct abm *abm = pipe_ctx->stream_res.abm;
>> -	uint32_t otg_inst = pipe_ctx->stream_res.tg->inst;
>> +	struct timing_generator *tg = pipe_ctx->stream_res.tg;
>>   	struct panel_cntl *panel_cntl = pipe_ctx->stream->link->panel_cntl;
>>   	struct dmcu *dmcu = pipe_ctx->stream->ctx->dc->res_pool->dmcu;
>> +	uint32_t otg_inst;
>> +
>> +	if (!abm && !tg && !panel_cntl)
>> +		return;
>> +
>> +	otg_inst = tg->inst;
> Is the "if" supposed to be using "||"s instead of "&&"s? I noticed
> Coverity complained "tg may be NULL" for the "tg->inst" dereference...
>
> -Kees

Thanks Kees!

It is fixed in the below commit:

commit ccc1e78470efb6572a71ba88d70995e8eee2f6e5
Author: Dan Carpenter <dan.carpenter at linaro.org>
Date:   Fri Feb 9 16:02:42 2024 +0300

     drm/amd/display: Fix && vs || typos

     These ANDs should be ORs or it will lead to a NULL dereference.

     Fixes: fb5a3d037082 ("drm/amd/display: Add NULL test for 'timing 
generator' in 'dcn21_set_pipe()'")
     Fixes: 886571d217d7 ("drm/amd/display: Fix 'panel_cntl' could be 
null in 'dcn21_set_backlight_level()'")
     Reviewed-by: Anthony Koo <anthony.koo at amd.com>
     Signed-off-by: Dan Carpenter <dan.carpenter at linaro.org>
     Signed-off-by: Hamza Mahfooz <hamza.mahfooz at amd.com>

-Srini