CVE-2022-48988: memcg: fix possible use-after-free in memcg_write_event_control()

Severity: high (CVSS 7.0 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-10-21 · updated 2026-08-04
Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: memcg: fix possible use-after-free in memcg_write_event_control() memcg_write_event_control() accesses the dentry->d_name of the specified control fd to route the write call. As a cgroup interface file can't be renamed, it's safe to access d_name as long as the specified file is a regular cgroup file. Also, as these cgroup interface files can't be removed before the directory, it's safe to access the parent too. Prior to 347c4a874710 ("memcg: remove cgroup_event->cft"), there was a call to __file_cft() which verified that the specified file is a regular cgroupfs file before further accesses. The cftype pointer returned from __file_cft() was no longer necessary and the commit inadvertently dropped the file type check with it allowing any file to slip through. With the invarients broken, the d_name and parent accesses can now race against renames and removals of arbitrary files and cause use-after-free's. Fix the bug by resurrecting the file type check in __file_cft(). Now that cgroupfs is implemented through kernfs, checking the file operations needs to go through a layer of indirection. Instead, let's check the superblock and dentry type.

Affected products

Linux kernel: from 3.14 before 4.14.302; from 4.15 before 4.19.269; from 4.20 before 5.4.227; from 5.5 before 5.10.159; from 5.11 before 5.15.83; from 5.16 before 6.0.13 — fixed in 4.14.302, 4.19.269, 5.10.159, 5.15.83, 5.4.227, 6.0.13

How to fix

Upgrade to a fixed version: Linux kernel 4.14.302, 4.19.269, 5.10.159, 5.15.83. Check the vendor advisory for mitigations.

References

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