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

[Hamza Mahfooz]

On 10/27/23 11:55, Lakha, Bhawanpreet wrote:
> [AMD Official Use Only - General]
>
>
>
> There was a consensus to use memset instead of {0}. I remember making 
> changes related to that previously.

Hm, seems like it's used rather consistently in the DM and in DC
though.

> Bhawan
>
> ------------------------------------------------------------------------
> *From:* Mahfooz, Hamza <Hamza.Mahfooz@xxxxxxx>
> *Sent:* October 27, 2023 11:53 AM
> *To:* Yuran Pereira <yuran.pereira@xxxxxxxxxxx>; airlied@xxxxxxxxx 
> <airlied@xxxxxxxxx>
> *Cc:* Li, Sun peng (Leo) <Sunpeng.Li@xxxxxxx>; Lakha, Bhawanpreet 
> <Bhawanpreet.Lakha@xxxxxxx>; Pan, Xinhui <Xinhui.Pan@xxxxxxx>; Siqueira, 
> Rodrigo <Rodrigo.Siqueira@xxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx 
> <linux-kernel@xxxxxxxxxxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx 
> <amd-gfx@xxxxxxxxxxxxxxxxxxxxx>; dri-devel@xxxxxxxxxxxxxxxxxxxxx 
> <dri-devel@xxxxxxxxxxxxxxxxxxxxx>; Deucher, Alexander 
> <Alexander.Deucher@xxxxxxx>; Koenig, Christian 
> <Christian.Koenig@xxxxxxx>; 
> linux-kernel-mentees@xxxxxxxxxxxxxxxxxxxxxxxxx 
> <linux-kernel-mentees@xxxxxxxxxxxxxxxxxxxxxxxxx>
> *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@xxxxxxxxxxx>
> > ---
> >    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
--
Hamza