CVE-2021-47254: gfs2: Fix use-after-free in gfs2_glock_shrink_scan

Severity: high (CVSS 7.8 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: 2024-05-21 · updated 2026-08-04
Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: gfs2: Fix use-after-free in gfs2_glock_shrink_scan The GLF_LRU flag is checked under lru_lock in gfs2_glock_remove_from_lru() to remove the glock from the lru list in __gfs2_glock_put(). On the shrink scan path, the same flag is cleared under lru_lock but because of cond_resched_lock(&lru_lock) in gfs2_dispose_glock_lru(), progress on the put side can be made without deleting the glock from the lru list. Keep GLF_LRU across the race window opened by cond_resched_lock(&lru_lock) to ensure correct behavior on both sides - clear GLF_LRU after list_del under lru_lock.

Affected products

Linux kernel: from 4.4.181 before 4.4.274; from 4.9.180 before 4.9.274; from 4.14.123 before 4.14.238; from 4.19.47 before 4.19.196; from 5.0.20 before 5.1; from 5.1.6 before 5.4.127 — fixed in 4.14.238, 4.19.196, 4.4.274, 4.9.274, 5.1, 5.10.45

How to fix

Upgrade to a fixed version: Linux kernel 4.14.238, 4.19.196, 4.4.274, 4.9.274. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2021-47254 or the next vulnerability affects your stack