CVE-2022-50010

In the Linux kernel, the following vulnerability has been resolved:

video: fbdev: i740fb: Check the argument of i740calcvclk()

Since the user can control the arguments of the ioctl() from the user space, under special arguments that may result in a divide-by-zero bug.

If the user provides an improper 'pixclock' value that makes the argumet of i740calcvclk() less than 'I740RFREQFIX', it will cause a divide-by-zero bug in: drivers/video/fbdev/i740fb.c:353 pbest = min(15, ilog2(I740MAXVCOFREQ / (freq / I740RFREQFIX)));

The following log can reveal it:

divide error: 0000 [#1] PREEMPT SMP KASAN PTI RIP: 0010:i740calcvclk drivers/video/fbdev/i740fb.c:353 [inline] RIP: 0010:i740fbdecodevar drivers/video/fbdev/i740fb.c:646 [inline] RIP: 0010:i740fbsetpar+0x163f/0x3b70 drivers/video/fbdev/i740fb.c:742 Call Trace: fbsetvar+0x604/0xeb0 drivers/video/fbdev/core/fbmem.c:1034 dofbioctl+0x234/0x670 drivers/video/fbdev/core/fbmem.c:1110 fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1189

Fix this by checking the argument of i740calcvclk() first.