linux-kernel - [BUG] video: fbdev: sis: possible uninitialized-variable access in SiS_SetCRT2FIFO

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Message-ID: <e0f988f3-f010-6299-d000-5c035e5f2e2e@gmail.com>
Date:   Sat, 31 Jul 2021 14:28:39 +0800
From:   Li Tuo <islituo@...il.com>
To:     thomas@...ischhofer.net
Cc:     dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, baijiaju1990@...il.com
Subject: [BUG] video: fbdev: sis: possible uninitialized-variable access in
 SiS_SetCRT2FIFO_300()

Hello,

Our static analysis tool finds a possible uninitialized-variable access 
in the sis driver in Linux 5.14.0-rc3:

At the beginning of the function SiS_SetCRT2FIFO_300(), the variable 
modeidindex is not initialized.
If the following conditions are false, it remains uninitialized.
5346:    if(!SiS_Pr->CRT1UsesCustomMode)
5438:    if(!SiS_Pr->UseCustomMode)

But it is accessed at:
5466:    colorth = SiS_GetColorDepth(SiS_Pr,CRT2ModeNo,modeidindex) >> 1;

I am not quite sure whether this possible uninitialized-variable access 
is real and how to fix it if it is real.
Any feedback would be appreciated, thanks!

Reported-by: TOTE Robot <oslab@...nghua.edu.cn>

Best wishes,
Tuo Li