CVE-2022-49554

/// Technical description

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

zsmalloc: fix races between asynchronous zspage free and page migration

The asynchronous zspage free worker tries to lock a zspage's entire page

list without defending against page migration. Since pages which haven't

yet been locked can concurrently migrate off the zspage page list while

lock_zspage() churns away, lock_zspage() can suffer from a few different

lethal races.

It can lock a page which no longer belongs to the zspage and unsafely

dereference page_private(), it can unsafely dereference a torn pointer to

the next page (since there's a data race), and it can observe a spurious

NULL pointer to the next page and thus not lock all of the zspage's pages

(since a single page migration will reconstruct the entire page list, and

create_page_chain() unconditionally zeroes out each list pointer in the

process).

Fix the races by using migrate_read_lock() in lock_zspage() to synchronize

with page migration.

/// 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