CVE-2020-25668

A flaw was found in Linux Kernel because access to the global variable fg_console is not properly synchronized leading to a use after free in con_font_op.

Weakness

The product utilizes multiple threads or processes to allow temporary access to a shared resource that can only be exclusive to one process at a time, but it does not properly synchronize these actions, which might cause simultaneous accesses of this resource by multiple threads or processes.

Affected Software

Extended Description

Synchronization refers to a variety of behaviors and mechanisms that allow two or more independently-operating processes or threads to ensure that they operate on shared resources in predictable ways that do not interfere with each other. Some shared resource operations cannot be executed atomically; that is, multiple steps must be guaranteed to execute sequentially, without any interference by other processes. Synchronization mechanisms vary widely, but they may include locking, mutexes, and semaphores. When a multi-step operation on a shared resource cannot be guaranteed to execute independent of interference, then the resulting behavior can be unpredictable. Improper synchronization could lead to data or memory corruption, denial of service, etc.

Potential Mitigations

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/25.html
• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/27.html
• https://cwe.mitre.org/data/definitions/29.html

References

• http://www.openwall.com/lists/oss-security/2020/10/30/1
• http://www.openwall.com/lists/oss-security/2020/11/04/3
• https://bugzilla.redhat.com/show_bug.cgi?id=1893287%2C
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=90bfdeef83f1d6c696039b6a917190dcbbad3220
• https://lists.debian.org/debian-lts-announce/2020/12/msg00015.html
• https://lists.debian.org/debian-lts-announce/2020/12/msg00027.html
• https://security.netapp.com/advisory/ntap-20210702-0005/
• https://www.openwall.com/lists/oss-security/2020/10/30/1%2C
• https://www.openwall.com/lists/oss-security/2020/11/04/3%2C