---
id: CVE-2026-46066
title: 'ceph: fix num_ops off-by-one when crypto allocation fails'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ceph: fix num_ops off-by-one when crypto allocation fails

  move_dirty_folio_in_page_array() may fail if the file is encrypted, the
  dirty folio is not the first in the b…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= d55207717ded95c8f2760a30e93319fa313186e6 <
    f65a96fe2467a9b184c6ae963d95a260a202c98e
  - >-
    Linux >= d55207717ded95c8f2760a30e93319fa313186e6 <
    5dd151799d826d3736ae60c2b22cbc9d96a2a613
  - >-
    Linux >= d55207717ded95c8f2760a30e93319fa313186e6 <
    6200f41d6fcf2ac7e24866431e381cbc914560e4
  - >-
    Linux >= d55207717ded95c8f2760a30e93319fa313186e6 <
    ba12c1e578890f6337a415b7dedf476c6d455105
  - >-
    Linux >= d55207717ded95c8f2760a30e93319fa313186e6 <
    a0d9555bf9eaeba34fe6b6bb86f442fe08ba3842
  - Linux 6.6
published: '2026-05-27'
updated: '2026-10-21'
sourceUpdated: '2026-10-21T12:41:16.157Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-46066'
references:
  - url: 'https://git.kernel.org/stable/c/f65a96fe2467a9b184c6ae963d95a260a202c98e'
  - url: 'https://git.kernel.org/stable/c/5dd151799d826d3736ae60c2b22cbc9d96a2a613'
  - url: 'https://git.kernel.org/stable/c/6200f41d6fcf2ac7e24866431e381cbc914560e4'
  - url: 'https://git.kernel.org/stable/c/ba12c1e578890f6337a415b7dedf476c6d455105'
  - url: 'https://git.kernel.org/stable/c/a0d9555bf9eaeba34fe6b6bb86f442fe08ba3842'
tags:
  - cve.org
epss: 0.0016
epssPercentile: 0.04784
ingestedAt: '2026-10-21T12:48:53.631Z'
---

## Overview

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

ceph: fix num_ops off-by-one when crypto allocation fails

move_dirty_folio_in_page_array() may fail if the file is encrypted, the
dirty folio is not the first in the batch, and it fails to allocate a
bounce buffer to hold the ciphertext. When that happens,
ceph_process_folio_batch() simply redirties the folio and flushes the
current batch -- it can retry that folio in a future batch.

However, if this failed folio is not contiguous with the last folio that
did make it into the batch, then ceph_process_folio_batch() has already
incremented `ceph_wbc->num_ops`; because it doesn't follow through and
add the discontiguous folio to the array, ceph_submit_write() -- which
expects that `ceph_wbc->num_ops` accurately reflects the number of
contiguous ranges (and therefore the required number of "write extent"
ops) in the writeback -- will panic the kernel:

    BUG_ON(ceph_wbc->op_idx + 1 != req->r_num_ops);

This issue can be reproduced on affected kernels by writing to
fscrypt-enabled CephFS file(s) with a 4KiB-written/4KiB-skipped/repeat
pattern (total filesize should not matter) and gradually increasing the
system's memory pressure until a bounce buffer allocation fails.

Fix this crash by decrementing `ceph_wbc->num_ops` back to the correct
value when move_dirty_folio_in_page_array() fails, but the folio already
started counting a new (i.e. still-empty) extent.

The defect corrected by this patch has existed since 2022 (see first
`Fixes:`), but another bug blocked multi-folio encrypted writeback until
recently (see second `Fixes:`). The second commit made it into 6.18.16,
6.19.6, and 7.0-rc1, unmasking the panic in those versions. This patch
therefore fixes a regression (panic) introduced by cac190c7674f.

## Affected

- `Linux >= d55207717ded95c8f2760a30e93319fa313186e6 < f65a96fe2467a9b184c6ae963d95a260a202c98e`
- `Linux >= d55207717ded95c8f2760a30e93319fa313186e6 < 5dd151799d826d3736ae60c2b22cbc9d96a2a613`
- `Linux >= d55207717ded95c8f2760a30e93319fa313186e6 < 6200f41d6fcf2ac7e24866431e381cbc914560e4`
- `Linux >= d55207717ded95c8f2760a30e93319fa313186e6 < ba12c1e578890f6337a415b7dedf476c6d455105`
- `Linux >= d55207717ded95c8f2760a30e93319fa313186e6 < a0d9555bf9eaeba34fe6b6bb86f442fe08ba3842`
- `Linux 6.6`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.