CVE-2021-46928: linux kernel — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: parisc: Clear stale IIR value on instruction access rights trap When a trap 7 (Instruction access rights) occurs, this means the CPU couldn't execute an instruction due to missing execute permissions on the memory region. In this case it seems the CPU didn't even fetched the instruction from memory and thus did not store it in the cr19 (IIR) register before calling the trap handler. So, the trap handler will find some random old stale value in cr19. This patch simply overwrites the stale IIR value with a constant magic "bad food" value (0xbaadf00d), in the hope people don't start to try to understand the various random IIR values in trap 7 dumps.

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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-755 CWE-755

Affected Products

Vendor	Product	Versions
linux	linux_kernel	< 5.10.90
linux	linux_kernel	5.11.0 — 5.15.13

References

Advisories & Patches

https://git.kernel.org/stable/c/484730e5862f6b872dca13840bed40fd7c60fa26 https://git.kernel.org/stable/c/d01e9ce1af6116f812491d3d3873d204f10ae0b8 https://git.kernel.org/stable/c/e96373f0a5f484bc1e193f9951dcb3adf24bf3f7 https://git.kernel.org/stable/c/484730e5862f6b872dca13840bed40fd7c60fa26 https://git.kernel.org/stable/c/d01e9ce1af6116f812491d3d3873d204f10ae0b8 https://git.kernel.org/stable/c/e96373f0a5f484bc1e193f9951dcb3adf24bf3f7

Frequently Asked Questions

What is CVE-2021-46928? +

In the Linux kernel, the following vulnerability has been resolved: parisc: Clear stale IIR value on instruction access rights trap When a trap 7 (Instruction access rights) occurs, this means the CPU couldn't execute an instruction due to missing execute permissions on the memory region. In this case it seems the CPU didn't even fetched the instruction from memory and thus did not store it in the cr19 (IIR) register before calling the trap handler. So, the trap handler will find some random old stale value in cr19. This patch simply overwrites the stale IIR value with a constant magic "bad food" value (0xbaadf00d), in the hope people don't start to try to understand the various random IIR values in trap 7 dumps. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2021-46928? +

CVE-2021-46928 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-2021-46928? +

CVE-2021-46928 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-2021-46928? +

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-2021-46928