Kernel: blkio memory leakage due to blkcg and some blkgs are not freed after they are made offline.
Summary
A flaw was found in the blkgs destruction path in block/blk-cgroup.c in the Linux kernel, leading to a cgroup blkio memory leakage problem. When a cgroup is being destroyed, cgroup_rstat_flush() is only called at css_release_work_fn(), which is called when the blkcg reference count reaches 0. This circular dependency will prevent blkcg and some blkgs from being freed after they are made offline. This issue may allow an attacker with a local access to cause system instability, such as an out of memory error. Affected products named by the advisory: Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9.2 Extended Update Support; Red Hat Enterprise Linux 9.
What this means
In plain English
A flaw was found in the blkgs destruction path in block/blk-cgroup.c in the Linux kernel, leading to a cgroup blkio memory leakage problem. When a cgroup is being destroyed, cgroup_rstat_flush() is only called at css_release_work_fn(), which is called when the blkcg reference count reaches 0. This circular dependency will prevent blkcg and some blkgs from being freed after they are made offline. This issue may allow an attacker with a local access to cause system instability, such as an out of memory error.
Recommended action
Primary action: update to a vendor-listed fixed release: 6.4-rc7. Temporary workaround: A flaw was found in the blkgs destruction path in block/blk-cgroup.c in the Linux kernel, leading to a cgroup blkio memory leakage problem.
Rewritten locally from the scraped official advisory data above; no generative API is used. The vendor advisory is authoritative.
- before 6.4-rc7
Official advisory · high-confidence parse· fetched 4 hours ago·verify at source
- 6.4-rc7
Official advisory · high-confidence parse· fetched 4 hours ago·verify at source
Mitigation checklist
- A flaw was found in the blkgs destruction path in block/blk-cgroup.c in the Linux kernel, leading to a cgroup blkio memory leakage problem.
Official advisory · high-confidence parse· fetched 4 hours ago·verify at source
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