[PATCH] drm/amdgpu: Fixes uninitialized variable usage in amdgpu_dm_setup_replay

[Lakha, Bhawanpreet]

[AMD Official Use Only - General]


There was a consensus to use memset instead of {0}. I remember making changes related to that previously.

Bhawan

________________________________
From: Mahfooz, Hamza <Hamza.Mahfooz at amd.com>
Sent: October 27, 2023 11:53 AM
To: Yuran Pereira <yuran.pereira at hotmail.com>; airlied at gmail.com <airlied at gmail.com>
Cc: Li, Sun peng (Leo) <Sunpeng.Li at amd.com>; Lakha, Bhawanpreet <Bhawanpreet.Lakha at amd.com>; Pan, Xinhui <Xinhui.Pan at amd.com>; Siqueira, Rodrigo <Rodrigo.Siqueira at amd.com>; linux-kernel at vger.kernel.org <linux-kernel at vger.kernel.org>; amd-gfx at lists.freedesktop.org <amd-gfx at lists.freedesktop.org>; dri-devel at lists.freedesktop.org <dri-devel at lists.freedesktop.org>; Deucher, Alexander <Alexander.Deucher at amd.com>; Koenig, Christian <Christian.Koenig at amd.com>; linux-kernel-mentees at lists.linuxfoundation.org <linux-kernel-mentees at lists.linuxfoundation.org>
Subject: Re: [PATCH] drm/amdgpu: Fixes uninitialized variable usage in amdgpu_dm_setup_replay

On 10/26/23 17:25, Yuran Pereira wrote:
> Since `pr_config` is not initialized after its declaration, the
> following operations with `replay_enable_option` may be performed
> when `replay_enable_option` is holding junk values which could
> possibly lead to undefined behaviour
>
> ```
>      ...
>      pr_config.replay_enable_option |= pr_enable_option_static_screen;
>      ...
>
>      if (!pr_config.replay_timing_sync_supported)
>          pr_config.replay_enable_option &= ~pr_enable_option_general_ui;
>      ...
> ```
>
> This patch initializes `pr_config` after its declaration to ensure that
> it doesn't contain junk data, and prevent any undefined behaviour
>
> Addresses-Coverity-ID: 1544428 ("Uninitialized scalar variable")
> Fixes: dede1fea4460 ("drm/amd/display: Add Freesync Panel DM code")
> Signed-off-by: Yuran Pereira <yuran.pereira at hotmail.com>
> ---
>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_replay.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_replay.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_replay.c
> index 32d3086c4cb7..40526507f50b 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_replay.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_replay.c
> @@ -23,6 +23,7 @@
>    *
>    */
>
> +#include <linux/string.h>
>   #include "amdgpu_dm_replay.h"
>   #include "dc.h"
>   #include "dm_helpers.h"
> @@ -74,6 +75,8 @@ bool amdgpu_dm_setup_replay(struct dc_link *link, struct amdgpu_dm_connector *ac
>        struct replay_config pr_config;

I would prefer setting pr_config = {0};

>        union replay_debug_flags *debug_flags = NULL;
>
> +     memset(&pr_config, 0, sizeof(pr_config));
> +
>        // For eDP, if Replay is supported, return true to skip checks
>        if (link->replay_settings.config.replay_supported)
>                return true;
--
Hamza

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