From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-89558: md/raid10: fix still_degraded being inverted in raid10_sync_request()
Date: Fri, 11 Sep 2026 21:44:07 +0200 [thread overview]
Message-ID: <2026091123-CVE-2026-89558-2b69@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
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.
The Linux kernel CVE team has assigned CVE-2026-89558 to this issue.
Affected and fixed versions
===========================
Issue introduced in 6.12 with commit fe6a19d40ceb44281905485f56dda715e3214e0e and fixed in 6.12.109 with commit 9bb8da6ecb330a5b1ac9b96f1e55f134a7aef1d4
Issue introduced in 6.12 with commit fe6a19d40ceb44281905485f56dda715e3214e0e and fixed in 6.18.50 with commit 0efabe6229dc683dbf6eeebd0f9fddc7971ed420
Issue introduced in 6.12 with commit fe6a19d40ceb44281905485f56dda715e3214e0e and fixed in 7.2.4 with commit 00449d752bee9c8787f42ea1bf533a9fb17f9b6b
Issue introduced in 6.12 with commit fe6a19d40ceb44281905485f56dda715e3214e0e and fixed in 7.3-rc1 with commit 47f1441b281decde6954a2fa82b4131637d685ac
Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.
Unaffected versions might change over time as fixes are backported to
older supported kernel versions. The official CVE entry at
https://cve.org/CVERecord/?id=CVE-2026-89558
will be updated if fixes are backported, please check that for the most
up to date information about this issue.
Affected files
==============
The file(s) affected by this issue are:
drivers/md/raid10.c
Mitigation
==========
The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes. Individual
changes are never tested alone, but rather are part of a larger kernel
release. Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all. If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
https://git.kernel.org/stable/c/9bb8da6ecb330a5b1ac9b96f1e55f134a7aef1d4
https://git.kernel.org/stable/c/0efabe6229dc683dbf6eeebd0f9fddc7971ed420
https://git.kernel.org/stable/c/00449d752bee9c8787f42ea1bf533a9fb17f9b6b
https://git.kernel.org/stable/c/47f1441b281decde6954a2fa82b4131637d685ac
reply other threads:[~2026-09-11 19:57 UTC|newest]
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