CVE-2024-40935: linux kernel Use-After-Free — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: cachefiles: flush all requests after setting CACHEFILES_DEAD In ondemand mode, when the daemon is processing an open request, if the kernel flags the cache as CACHEFILES_DEAD, the cachefiles_daemon_write() will always return -EIO, so the daemon can't pass the copen to the kernel. Then the kernel process that is waiting for the copen triggers a hung_task. Since the DEAD state is irreversible, it can only be exited by closing /dev/cachefiles. Therefore, after calling cachefiles_io_error() to mark the cache as CACHEFILES_DEAD, if in ondemand mode, flush all requests to avoid the above hungtask. We may still be able to read some of the cached data before closing the fd of /dev/cachefiles. Note that this relies on the patch that adds reference counting to the req, otherwise it may UAF.

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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	5.19 — 6.1.95
linux	linux_kernel	6.2 — 6.6.35
linux	linux_kernel	6.7 — 6.9.6
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/320ba9cbca78be79c912143bbba1d1b35ca55cf0 https://git.kernel.org/stable/c/3bf0b8030296e9ee60d3d4c15849ad9ac0b47081 https://git.kernel.org/stable/c/85e833cd7243bda7285492b0653c3abb1e2e757b https://git.kernel.org/stable/c/e73fac95084839c5178d97e81c6a2051251bdc00 https://git.kernel.org/stable/c/320ba9cbca78be79c912143bbba1d1b35ca55cf0 https://git.kernel.org/stable/c/3bf0b8030296e9ee60d3d4c15849ad9ac0b47081 https://git.kernel.org/stable/c/85e833cd7243bda7285492b0653c3abb1e2e757b https://git.kernel.org/stable/c/e73fac95084839c5178d97e81c6a2051251bdc00

Other References

https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html

Frequently Asked Questions

What is CVE-2024-40935? +

In the Linux kernel, the following vulnerability has been resolved: cachefiles: flush all requests after setting CACHEFILES_DEAD In ondemand mode, when the daemon is processing an open request, if the kernel flags the cache as CACHEFILES_DEAD, the cachefiles_daemon_write() will always return -EIO, so the daemon can't pass the copen to the kernel. Then the kernel process that is waiting for the copen triggers a hung_task. Since the DEAD state is irreversible, it can only be exited by closing /dev/cachefiles. Therefore, after calling cachefiles_io_error() to mark the cache as CACHEFILES_DEAD, if in ondemand mode, flush all requests to avoid the above hungtask. We may still be able to read some of the cached data before closing the fd of /dev/cachefiles. Note that this relies on the patch that adds reference counting to the req, otherwise it may UAF. It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2024-40935? +

CVE-2024-40935 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-2024-40935? +

CVE-2024-40935 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-2024-40935? +

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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