CVE-2021-47195: linux kernel Use-After-Free — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: spi: fix use-after-free of the add_lock mutex Commit 6098475d4cb4 ("spi: Fix deadlock when adding SPI controllers on SPI buses") introduced a per-controller mutex. But mutex_unlock() of said lock is called after the controller is already freed: spi_unregister_controller(ctlr) -> put_device(&ctlr->dev) -> spi_controller_release(dev) -> mutex_unlock(&ctrl->add_lock) Move the put_device() after the mutex_unlock().

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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-416 Use After Free

Affected Products

Vendor	Product	Versions
linux	linux_kernel	< 5.15.5

References

Advisories & Patches

https://git.kernel.org/stable/c/37330f37f6666c7739a44b2b6b95b047ccdbed2d https://git.kernel.org/stable/c/6c53b45c71b4920b5e62f0ea8079a1da382b9434 https://git.kernel.org/stable/c/37330f37f6666c7739a44b2b6b95b047ccdbed2d https://git.kernel.org/stable/c/6c53b45c71b4920b5e62f0ea8079a1da382b9434

Other References

https://git.kernel.org/stable/c/11eab327a2a8bd36c38afbff920ae1bd45588dd4 https://git.kernel.org/stable/c/54c2c96eafcfd242e52e932ab54ace4784efe1dd

Frequently Asked Questions

What is CVE-2021-47195? +

In the Linux kernel, the following vulnerability has been resolved: spi: fix use-after-free of the add_lock mutex Commit 6098475d4cb4 ("spi: Fix deadlock when adding SPI controllers on SPI buses") introduced a per-controller mutex. But mutex_unlock() of said lock is called after the controller is already freed: spi_unregister_controller(ctlr) -> put_device(&ctlr->dev) -> spi_controller_release(dev) -> mutex_unlock(&ctrl->add_lock) Move the put_device() after the mutex_unlock(). It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2021-47195? +

CVE-2021-47195 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-2021-47195? +

CVE-2021-47195 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-2021-47195? +

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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