Cloudanix VulnDB

CVE-2026-89578

None

CVSS

—

EPSS

0.2%

Published

Sep 11, 2026

CISA due date

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Cloudanix analysis

Schedule a fix SSVC: Track

A bug in Linux storage handling can cause the system to freeze when certain programs write directly to mirrored disks, requiring a reboot to fix.

Exploitation
Local Privilege
Attacker needs
Local User
Complexity
Moderate
Impact
Denial Of Service
Component
OS kernel
Class
Denial of service
Remediation
Upgrade
Effort
Medium
Patch risk
Low

What it actually does

A flaw in dm-io's do_region() for DM_IO_BIO requests caused sector-based accounting to lose sub-sector fragments on misaligned O_DIRECT buffers, resulting in an infinite loop that submits empty bios and hangs I/O instead of properly cloning the source bio's biovec via bio_alloc_clone().

Why it matters to the business

Systems using device-mapper targets such as dm-mirror with direct I/O from misaligned buffers can experience I/O hangs that render storage unavailable, disrupting workloads and requiring reboots or manual intervention to recover.

How an attack unfolds

An attacker with local access submits a misaligned O_DIRECT read or write through a dm-mirror device; the kernel's sector accounting in do_region() drops the final fragment, causing repeated submission of zero-length bios that never complete and hang the I/O path.

How to fix it

Update the Linux kernel to a version containing the bio_alloc_clone() change that eliminates the manual biovec copy path for DM_IO_BIO requests; rebuild and reboot with the corrected kernel image.

How to confirm the fix worked

Confirm the running kernel contains the dm-io bio clone fix by inspecting the source or changelog for removal of the open-coded bvec dpages helpers and sector accounting loop; test with misaligned O_DIRECT I/O to dm-mirror to verify completion without hang.

Typical attack path

  1. Obtain local unprivileged access on a Linux system using dm-mirror or similar targets
  2. Open a file or device with O_DIRECT and a buffer whose page alignment produces a non-sector-multiple length
  3. Issue a read or write that triggers DM_IO_BIO handling in dm-io
  4. Trigger the infinite loop in do_region() that submits empty bios
  5. Observe I/O hang and resulting denial of service on the affected block device

How to detect it

Review kernel logs for repeated empty bio submissions or I/O stalls on dm devices; examine process traces showing blocked tasks in dm-io or block layer during direct I/O; correlate with application logs indicating hung storage operations.

What your security team should do

  • Prioritize kernel updates on any system exposing dm-mirror or dm-io to untrusted local users
  • Audit workloads for O_DIRECT usage with dm targets and consider disabling direct I/O where possible until patched
  • Monitor kernel update channels for backports of the bio_alloc_clone() change

The record

In the Linux kernel, the following vulnerability has been resolved: dm-io: clone the source bio instead of copying its biovec For DM_IO_BIO requests, do_region() built each destination bio by walking the source bio's biovec and re-adding the pages one at a time, tracking the remaining transfer in sectors. The vector lengths are byte granular and need not be sector aligned (e.g. a misaligned O_DIRECT buffer split across pages), so the sector-based accounting could lose a sub-sector fragment: to_sector() truncated the remainder and the outer loop spun forever submitting empty bios, hanging the I/O. There is no need to rebuild the biovec at all. The destination reads into (or writes from) exactly the same pages as the source bio, so the bio can simply clone the source's biovec with bio_alloc_clone() and remap it to the target device. The clone inherits the source's iterator and alignment, and the block layer splits it to the target's limits on submission, so the whole region maps to a single cloned bio with no manual page copying or sector accounting. This removes the per-page copy path (and its open-coded bvec dpages helpers) for bio-backed I/O and fixes the hang on misaligned direct I/O to a dm-mirror device. Page-list, vma and kmem sources keep the existing copy path.

Affected packages

Ecosystem Package Introduced Fixed