CVE-2022-49978: linux kernel — Fix

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

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CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-369 CWE-369

Affected Products

Vendor	Product	Versions
linux	linux_kernel	< 4.9.327
linux	linux_kernel	4.10 — 4.14.292
linux	linux_kernel	4.15 — 4.19.257
linux	linux_kernel	4.20 — 5.4.212
linux	linux_kernel	5.5 — 5.10.141
linux	linux_kernel	5.11 — 5.15.65
linux	linux_kernel	5.16 — 5.19.7
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

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

Frequently Asked Questions

What is CVE-2022-49978? +

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 It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2022-49978? +

CVE-2022-49978 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2022-49978? +

CVE-2022-49978 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2022-49978? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2022-49978