CVE-2026-23157

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

btrfs: do not strictly require dirty metadata threshold for metadata writepages

[BUG]

There is an internal report that over 1000 processes are

waiting at the io_schedule_timeout() of balance_dirty_pages(), causing

a system hang and trigger a kernel coredump.

The kernel is v6.4 kernel based, but the root problem still applies to

any upstream kernel before v6.18.

[CAUSE]

From Jan Kara for his wisdom on the dirty page balance behavior first.

This cgroup dirty limit was what was actually playing the role here

because the cgroup had only a small amount of memory and so the dirty

limit for it was something like 16MB.

Dirty throttling is responsible for enforcing that nobody can dirty

(significantly) more dirty memory than there's dirty limit. Thus when

a task is dirtying pages it periodically enters into balance_dirty_pages()

and we let it sleep there to slow down the dirtying.

When the system is over

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References