CVE-2024-57942: netfs: Fix ceph copy to cache on write-begin

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-01-21 · updated 2026-06-17

Description

In the Linux kernel, the following vulnerability has been resolved: netfs: Fix ceph copy to cache on write-begin At the end of netfs_unlock_read_folio() in which folios are marked appropriately for copying to the cache (either with by being marked dirty and having their private data set or by having PG_private_2 set) and then unlocked, the folio_queue struct has the entry pointing to the folio cleared. This presents a problem for netfs_pgpriv2_write_to_the_cache(), which is used to write folios marked with PG_private_2 to the cache as it expects to be able to trawl the folio_queue list thereafter to find the relevant folios, leading to a hang. Fix this by not clearing the folio_queue entry if we're going to do the deprecated copy-to-cache. The clearance will be done instead as the folios are written to the cache. This can be reproduced by starting cachefiles, mounting a ceph filesystem with "-o fsc" and writing to it.

Affected products

Linux kernel: from 6.12 before 6.12.10; 6.13-rc1, 6.13-rc2, 6.13-rc3, 6.13-rc4, 6.13-rc5, 6.13-rc6 — fixed in 6.12.10

How to fix

Upgrade to a fixed version: Linux kernel 6.12.10. Check the vendor advisory for mitigations.

References

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