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

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Message-ID: <5981f677-3347-1450-f787-853e97496bd4@amd.com>
Date:   Thu, 22 Aug 2019 19:21:12 +0000
From:   Harry Wentland <hwentlan@....com>
To:     Colin King <colin.king@...onical.com>,
        "Wentland, Harry" <Harry.Wentland@....com>,
        "Li, Sun peng (Leo)" <Sunpeng.Li@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        "Zhou, David(ChunMing)" <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
CC:     "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][drm-next] drm/amd/display: fix a potential null pointer
 dereference

On 2019-08-16 6:10 p.m., Colin King wrote:
> From: Colin Ian King <colin.king@...onical.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@...onical.com>

Reviewed-by: Harry Wentland <harry.wentland@....com>

Harry

> ---
>  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)
> @@ -1244,6 +1244,7 @@ static bool calc_pll_max_vco_construct(
>  	if (init_data->bp->fw_info_valid)
>  		return false;
>  
> +	fw_info = &init_data->bp->fw_info;
>  	calc_pll_cs->ctx = init_data->ctx;
>  	calc_pll_cs->ref_freq_khz = fw_info->pll_info.crystal_frequency;
>  	calc_pll_cs->min_vco_khz =
>