CVE-2021-47635

Name of the Vulnerable Software and Affected Versions Linux kernel versions prior to 5.15.0-rc5

Description A bug in the Linux kernel's UBIFS (Unsorted Block Image File System) has been identified, which can cause a page migration issue. The problem arises when the PG private flag is set on a page without incrementing the reference count. This can lead to a situation where the page migration process believes the page is not in use by any other processes and attempts to migrate it, resulting in concurrent access to the page reference count. This can cause a kernel bug, leading to a crash.

Recommendations For Linux kernel versions prior to 5.15.0-rc5, consider applying the fix to increment the reference count when setting the PG private flag on a page. As a temporary workaround, consider disabling the ubifs migrate page() function until a patch is available. Restrict access to the vulnerable ubifs module to minimize the risk of exploitation. Avoid using the page cache get speculative() function in the affected API endpoint until the issue is resolved.