In the Linux kernel, the following vulnerability has been resolved: fbdev: fbpm2fb: Avoid potential divide by zero error In do_fb_ioctl()
of fbmem.c, if cmd is FBIOPUTVSCREENINFO, var will be copied from user, then go through fb_set_var()
and info->fbops->fb_check_var()
which could may be pm2fb_check_var()
. Along the path, var->pixclock
won't be modified. This function checks whether reciprocal of var->pixclock
is too high. If var->pixclock
is zero, there will be a divide by zero error. So, it is necessary to check whether denominator is zero to avoid crash. As this bug is found by Syzkaller, logs are listed below. divide error in pm2fbcheckvar Call Trace: <TASK> fbsetvar+0x367/0xeb0 drivers/video/fbdev/core/fbmem.c:1015 dofbioctl+0x234/0x670 drivers/video/fbdev/core/fbmem.c:1110 fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1189