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CRITICAL Introduced in 6.12

md StillDegraded Corruption

CVE-2026-89558

CVSS 9.8 / 10.0 NVD

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

KernelScan AI5.1MEDIUM

01

In the Linux kernel, the following vulnerability has been resolved: md/raid10: fix still_degraded being inverted in raid10_sync_request() Commit fe6a19d40ceb ("md/md-bitmap: merge md_bitmap_start_sync() into bitmap_operations") converted still_degraded from int to bool, but inverted the assignment in the loop that checks whether the array will still be degraded after the current device is recovered: "still_degraded = 1" became "still_degraded = false". As a result, recovering a device while another mirror is still missing calls md_bitmap_start_sync() with degraded == false, which clears bitmap bits that the still-missing device needs. When that device is re-added, its bitmap-based recovery finds the bits already cleared and skips every region written while the array was degraded, so it is marked In_sync while holding stale data: silent corruption. Reproducer (raid10 near=2, 4 disks, internal bitmap): - fail and remove one disk of each mirror pair - write to the degraded array - re-add both disks and let recovery finish - "check" reports mismatch_cnt=262272 after 256 MiB of degraded writes and file contents differ; the second disk's "recovery" completes in milliseconds because everything is skipped The same conversion in raid1 got it right (still_degraded = true). Restore the correct value.

02

Engine v0.6.0

Risk summary

A logic inversion in the RAID10 recovery code causes silent data corruption when a disk is re-added to a degraded array with an internal bitmap. The re-added disk is marked in-sync while holding stale data, and the array reports consistency when it is not. An attacker with root or CAP_SYS_ADMIN who can manage RAID disks can trigger this on any RAID10 array using internal bitmaps.

Affecteddrivers/md/raid10.c (md/raid10)

Vulnerability analysis

A refactoring of the RAID10 recovery path inverted a boolean that tracks whether the array will remain degraded after the current device finishes recovering. The code now reports the array as not degraded when it actually is, causing the bitmap to clear synchronization bits for regions that a still-missing mirror device needs. When that device is later re-added, its bitmap-based recovery sees those bits already cleared, skips every affected region, and marks the disk in-sync while it holds stale data — producing silent on-disk corruption. The fix restores the correct boolean value so the bitmap is handled properly during degraded recovery. Triggering this requires root or equivalent privileges to fail, remove, and re-add disks on a RAID10 array configured with an internal bitmap.

03

BranchIntroducedFixed inPatch commit
6.126.126.12.1099bb8da6ecb33
6.186.126.18.500efabe6229dc
7.26.127.2.400449d752bee
mainline6.127.3-rc147f1441b281d