Re: [PATCH][drm-next] drm/amd/display: fix a potential null pointer dereference

[Dan Carpenter <dan.carpenter@oracle.com>]

On Fri, Aug 16, 2019 at 11:10:11PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> Currently the pointer init_data is dereferenced on the assignment
> of fw_info before init_data is sanity checked to see if it is null.
> Fix te potential null pointer dereference on init_data by only
> performing dereference after it is null checked.
> 
> Addresses-Coverity: ("Dereference before null check")
> Fixes: 9adc8050bf3c ("drm/amd/display: make firmware info only load once during dc_bios create")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c b/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
> index bee81bf288be..926954c804a6 100644
> --- a/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
> +++ b/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
> @@ -1235,7 +1235,7 @@ static bool calc_pll_max_vco_construct(
>  			struct calc_pll_clock_source_init_data *init_data)
>  {
>  	uint32_t i;
> -	struct dc_firmware_info *fw_info = &init_data->bp->fw_info;
> +	struct dc_firmware_info *fw_info;
>  	if (calc_pll_cs == NULL ||
>  			init_data == NULL ||
>  			init_data->bp == NULL)

init_data can't be NULL.  I'm mostly pointing this out because that NULL
check is written so higgledy-piggledy.  At first I thought this was
staging code so I was planning to ignore the patch.  :P

regards,
dan carpenter