CVE-2022-49978

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> fbdev: fb_pm2fb: Avoid potential divide by zero error<br /> <br /> In `do_fb_ioctl()` of fbmem.c, if cmd is FBIOPUT_VSCREENINFO, var will be<br /> copied from user, then go through `fb_set_var()` and<br /> `info-&gt;fbops-&gt;fb_check_var()` which could may be `pm2fb_check_var()`.<br /> Along the path, `var-&gt;pixclock` won&amp;#39;t be modified. This function checks<br /> whether reciprocal of `var-&gt;pixclock` is too high. If `var-&gt;pixclock` is<br /> zero, there will be a divide by zero error. So, it is necessary to check<br /> whether denominator is zero to avoid crash. As this bug is found by<br /> Syzkaller, logs are listed below.<br /> <br /> divide error in pm2fb_check_var<br /> Call Trace:<br /> <br /> fb_set_var+0x367/0xeb0 drivers/video/fbdev/core/fbmem.c:1015<br /> do_fb_ioctl+0x234/0x670 drivers/video/fbdev/core/fbmem.c:1110<br /> fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1189