fbdev: sis: Error out if pixclock equals zero
[ Upstream commit e421946be7d9bf545147bea8419ef8239cb7ca52 ] The userspace program could pass any values to the driver through ioctl() interface. If the driver doesn't check the value of pixclock, it may cause divide-by-zero error. In sisfb_check_var(), var->pixclock is used as a divisor to caculate drate before it is checked against zero. Fix this by checking it at the beginning. This is similar to CVE-2022-3061 in i740fb which was fixed by commit 15cf0b8. Signed-off-by: Fullway Wang <fullwaywang@outlook.com> Signed-off-by: Helge Deller <deller@gmx.de> Signed-off-by: Sasha Levin <sashal@kernel.org>
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@ -1474,6 +1474,8 @@ sisfb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
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vtotal = var->upper_margin + var->lower_margin + var->vsync_len;
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if (!var->pixclock)
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return -EINVAL;
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pixclock = var->pixclock;
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if((var->vmode & FB_VMODE_MASK) == FB_VMODE_NONINTERLACED) {
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