CVE-2024-26832: mm: zswap: fix missing folio cleanup in writeback race path

Vulnerability summary

CVE-2024-26832 is a medium (CVSS 5.5) Incomplete Cleanup vulnerability in linux. EPSS estimates a 0.22% chance of exploitation in the next 30 days, higher than 12.8% of scored vulnerabilities.

Timeline

1. 17-04-2024
   PublishedVulnerability first disclosed.
2. 23-05-2026
   Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: mm: zswap: fix missing folio cleanup in writeback race path In zswap_writeback_entry(), after we get a folio from __read_swap_cache_async(), we grab the tree lock again to check that the swap entry was not invalidated and recycled. If it was, we delete the folio we just added to the swap cache and exit. However, __read_swap_cache_async() returns the folio locked when it is newly allocated, which is always true for this path, and the folio is ref'd. Make sure to unlock and put the folio before returning. This was discovered by code inspection, probably because this path handles a race condition that should not happen often, and the bug would not crash the system, it will only strand the folio indefinitely.

• CWE-459Incomplete CleanupThe product does not properly "clean up" and remove temporary or supporting resources after they have been used.