CVE-2022-49554 Information

Mar 01, 2025 cve

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.

Reference

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