CVE-2021-47342: linux kernel Use-After-Free — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: ext4: fix possible UAF when remounting r/o a mmp-protected file system After commit 618f003199c6 ("ext4: fix memory leak in ext4_fill_super"), after the file system is remounted read-only, there is a race where the kmmpd thread can exit, causing sbi->s_mmp_tsk to point at freed memory, which the call to ext4_stop_mmpd() can trip over. Fix this by only allowing kmmpd() to exit when it is stopped via ext4_stop_mmpd(). Bug-Report-Link: <[email protected]>

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CVSS v3.1 Score

7.8

HIGH

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

Weakness Type (CWE)

CWE-416 Use After Free

Affected Products

Vendor	Product	Versions
linux	linux_kernel	< 5.10.77
linux	linux_kernel	5.11 — 5.13.3

References

Advisories & Patches

https://git.kernel.org/stable/c/61bb4a1c417e5b95d9edb4f887f131de32e419cb https://git.kernel.org/stable/c/7ed572cdf11081f8f9e07abd4bea56a3f2c4edbd https://git.kernel.org/stable/c/b663890d854403e566169f7e90aed5cd6ff64f6b https://git.kernel.org/stable/c/61bb4a1c417e5b95d9edb4f887f131de32e419cb https://git.kernel.org/stable/c/7ed572cdf11081f8f9e07abd4bea56a3f2c4edbd https://git.kernel.org/stable/c/b663890d854403e566169f7e90aed5cd6ff64f6b

Frequently Asked Questions

What is CVE-2021-47342? +

In the Linux kernel, the following vulnerability has been resolved: ext4: fix possible UAF when remounting r/o a mmp-protected file system After commit 618f003199c6 ("ext4: fix memory leak in ext4_fill_super"), after the file system is remounted read-only, there is a race where the kmmpd thread can exit, causing sbi->s_mmp_tsk to point at freed memory, which the call to ext4_stop_mmpd() can trip over. Fix this by only allowing kmmpd() to exit when it is stopped via ext4_stop_mmpd(). Bug-Report-Link: <[email protected]> It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2021-47342? +

CVE-2021-47342 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2021-47342? +

CVE-2021-47342 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-2021-47342? +

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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