CVE-2022-50102

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

video: fbdev: arkfb: Fix a divide-by-zero bug in ark_set_pixclock()

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 in: drivers/video/fbdev/arkfb.c:784: ark_set_pixclock(info, (hdiv * info->var.pixclock) / hmul); with hdiv=1, pixclock=1 and hmul=2 you end up with (1*1)/2 = (int) 0. and then in: drivers/video/fbdev/arkfb.c:504: rv = dac_set_freq(par->dac, 0, 1000000000 / pixclock); well get a division-by-zero.

The following log can reveal it:

divide error: 0000 [#1] PREEMPT SMP KASAN PTI RIP: 0010:ark_set_pixclock drivers/video/fbdev/arkfb.c:504 [inline] RIP: 0010:arkfb_set_par+0x10fc/0x24c0 drivers/video/fbdev/arkfb.c:784 Call Trace: fb_set_var+0x604/0xeb0 drivers/video/fbdev/core/fbmem.c:1034 do_fb_ioctl+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 ark_set_pixclock() first.

Affected Software

References

• https://git.kernel.org/stable/c/0288fa799e273b08839037499d704dc7bdc13e9a
• https://git.kernel.org/stable/c/15661642511b2b192077684a89f42a8d95d54286
• https://git.kernel.org/stable/c/236c1502520b7b08955467ec2e50b3232e34f1f9
• https://git.kernel.org/stable/c/2f1c4523f7a3aaabe7e53d3ebd378292947e95c8
• https://git.kernel.org/stable/c/76b3f0a0b56e53a960a14624a0f48b3d94b5e7e7
• https://git.kernel.org/stable/c/9ebc5031958c1f3a2795e4533b4091d77c738d14
• https://git.kernel.org/stable/c/a249e1b89ca25e1c34bdf96154e3f6224a91a9af
• https://git.kernel.org/stable/c/b9a66f23612b84617e04412169e155a4b92f632d