CVE-2022-49978: fbdev: fb_pm2fb: Avoid potential divide by zero error

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-06-18 · updated 2026-06-17
Weakness: CWE-369

Description

In the Linux kernel, the following vulnerability has been resolved: fbdev: fb_pm2fb: Avoid potential divide by zero error In `do_fb_ioctl()` of fbmem.c, if cmd is FBIOPUT_VSCREENINFO, 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 pm2fb_check_var Call Trace: <TASK> fb_set_var+0x367/0xeb0 drivers/video/fbdev/core/fbmem.c:1015 do_fb_ioctl+0x234/0x670 drivers/video/fbdev/core/fbmem.c:1110 fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1189

Affected products

Linux kernel: before 4.9.327; from 4.10 before 4.14.292; from 4.15 before 4.19.257; from 4.20 before 5.4.212; from 5.5 before 5.10.141; from 5.11 before 5.15.65 — fixed in 4.14.292, 4.19.257, 4.9.327, 5.10.141, 5.15.65, 5.19.7

How to fix

Upgrade to a fixed version: Linux kernel 4.14.292, 4.19.257, 4.9.327, 5.10.141. Check the vendor advisory for mitigations.

References

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