linux-kernel - Re: [PATCH] drm/ast: Avoid possible NULL dereference

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 for Android: free password hash cracker in your pocket

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

Message-ID: <07ffd0f9-853c-8aca-d2b6-8f643f83c940@nfschina.com>
Date:   Mon, 21 Aug 2023 15:16:21 +0800
From:   Su Hui <suhui@...china.com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        airlied@...hat.com, tzimmermann@...e.de, airlied@...il.com,
        daniel@...ll.ch
Cc:     eich@...e.de, tiwai@...e.de, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] drm/ast: Avoid possible NULL dereference

On 2023/8/21 15:04, Christophe JAILLET wrote:
> Le 21/08/2023 à 08:22, Su Hui a écrit :
>> smatch error:
>> drivers/gpu/drm/ast/ast_dp501.c:227 ast_launch_m68k() error:
>> we previously assumed 'ast->dp501_fw' could be null (see line 223)
>>
>> when "!ast->dp501_fw" and "ast_load_dp501_microcode(dev) >= 0" is true,
>> there will be a NULL dereference of 'ast->dp501_fw'.
>>
>> Fixes: 12f8030e05c6 ("drm/ast: Actually load DP501 firmware when 
>> required")
>> Signed-off-by: Su Hui <suhui@...china.com>
>> ---
>>   drivers/gpu/drm/ast/ast_dp501.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/ast/ast_dp501.c 
>> b/drivers/gpu/drm/ast/ast_dp501.c
>> index 1bc35a992369..d9f3a0786a6f 100644
>> --- a/drivers/gpu/drm/ast/ast_dp501.c
>> +++ b/drivers/gpu/drm/ast/ast_dp501.c
>> @@ -224,8 +224,10 @@ static bool ast_launch_m68k(struct drm_device *dev)
>>                   ast_load_dp501_microcode(dev) < 0)
>>                   return false;
>>   -            fw_addr = (u8 *)ast->dp501_fw->data;
>> -            len = ast->dp501_fw->size;
>> +            if (ast->dp501_fw) {
>> +                fw_addr = (u8 *)ast->dp501_fw->data;
>> +                len = ast->dp501_fw->size;
>> +            }
>>           }
>>           /* Get BootAddress */
>>           ast_moutdwm(ast, 0x1e6e2000, 0x1688a8a8);
>
> Hi,
>
> this looks like a false positive.
>
> If "!ast->dp501_fw", and ast_load_dp501_microcode()>=0, then 
> ast_load_dp501_microcode() will set a valid value in ast->dp501_fw.

Hi,

Sorry for the noise, you are right, this is a false positive.
I will take more careful next time.

Su Hui

>
> CJ