linux-kernel - Re: [PATCH] drm/amdgpu: Fixes uninitialized variable usage in amdgpu_dm_setup

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <403a0750-361e-4218-8c83-a085966349e4@gmail.com>
Date:   Mon, 30 Oct 2023 16:52:25 +0100
From:   Christian König <ckoenig.leichtzumerken@...il.com>
To:     Yuran Pereira <yuran.pereira@...mail.com>,
        Hamza Mahfooz <hamza.mahfooz@....com>
Cc:     "Li, Sun peng (Leo)" <Sunpeng.Li@....com>,
        "Lakha, Bhawanpreet" <Bhawanpreet.Lakha@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        "Siqueira, Rodrigo" <Rodrigo.Siqueira@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "airlied@...il.com" <airlied@...il.com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        "linux-kernel-mentees@...ts.linuxfoundation.org" 
        <linux-kernel-mentees@...ts.linuxfoundation.org>
Subject: Re: [PATCH] drm/amdgpu: Fixes uninitialized variable usage in
 amdgpu_dm_setup_replay

Am 28.10.23 um 02:48 schrieb Yuran Pereira:
> Hello,
> On Fri, Oct 27, 2023 at 11:57:45AM -0400, Hamza Mahfooz wrote:
>> 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.
>>
> Have you decided which one should be used?
>
> Should I submit a v2 patch using {0} instead of memset?

The problem is that {0} doesn't initialize padding fields in structures.

So what can happen are problems like leaking bytes to userspace or 
getting unstable hash keys etc...

So I think memset() is usually preferred and that not only counts for Linux.

Regards,
Christian.

>
>
> Yuran Pereira
>>> Bhawan
>>>
>>> ------------------------------------------------------------------------
>>> *From:* Mahfooz, Hamza <Hamza.Mahfooz@....com>
>>> *Sent:* October 27, 2023 11:53 AM
>>> *To:* Yuran Pereira <yuran.pereira@...mail.com>; airlied@...il.com
>>> <airlied@...il.com>
>>> *Cc:* Li, Sun peng (Leo) <Sunpeng.Li@....com>; Lakha, Bhawanpreet
>>> <Bhawanpreet.Lakha@....com>; Pan, Xinhui <Xinhui.Pan@....com>; Siqueira,
>>> Rodrigo <Rodrigo.Siqueira@....com>; linux-kernel@...r.kernel.org
>>> <linux-kernel@...r.kernel.org>; amd-gfx@...ts.freedesktop.org
>>> <amd-gfx@...ts.freedesktop.org>; dri-devel@...ts.freedesktop.org
>>> <dri-devel@...ts.freedesktop.org>; Deucher, Alexander
>>> <Alexander.Deucher@....com>; Koenig, Christian
>>> <Christian.Koenig@....com>;
>>> linux-kernel-mentees@...ts.linuxfoundation.org
>>> <linux-kernel-mentees@...ts.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@...mail.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
>>>
>> -- 
>> Hamza
>>