CVE-2024-50066

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

mm/mremap: fix move_normal_pmd/retract_page_tables race

In mremap(), move_page_tables() looks at the type of the PMD entry and the

specified address range to figure out by which method the next chunk of

page table entries should be moved.

At that point, the mmap_lock is held in write mode, but no rmap locks are

held yet. For PMD entries that point to page tables and are fully covered

by the source address range, move_pgt_entry(NORMAL_PMD, ...) is called,

which first takes rmap locks, then does move_normal_pmd().

move_normal_pmd() takes the necessary page table locks at source and

destination, then moves an entire page table from the source to the

destination.

The problem is: The rmap locks, which protect against concurrent page

table removal by retract_page_tables() in the THP code, are only taken

after the PMD entry has been read and it has been decided how to move it.

So we can race as follows (with two proces

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References